Caribbean - Central America Weather

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
406 PM AST Mon Mar 19 2018

.SYNOPSIS...A seasonal weather pattern is expected to prevail
much of the workweek with afternoon showers developing each day
over the Cordillera Central and west sections of Puerto Rico. A
frontal boundary will move close to the local isles Friday into
the upcoming weekend.

&&

.SHORT TERM...Tonight through Wednesday...

As expected, scattered to numerous showers developed this afternoon
over the Cordillera Central and west sections of Puerto Rico. These
showers are expected to dissipated this evening, leaving clear to
partly cloudy skies across the region. Low temperatures would be in
the low 70s across lower elevations and in the upper 60s at higher
elevations. Brief isolated passing showers, if any, are expected
mainly across windward areas tonight, elsewhere rain-free conditions
will prevail.

Although a mid to upper level ridge will build across the local
isles through the forecast cycle, precipitable water is not expected
to decrease significantly. PW values will remain near the normal
range, which is enough to combine with sea breezes to result in
afternoon showers both days. ESE winds continue, therefore afternoon
showers will be focused over W and NW PR.

.LONG TERM...Thu thru Tue.../issued 442 AM AST Mon Mar 19 2018/

Thursday, A vertical stacked ridge will promote fair weather earlier
on Thursday but, the ridging will begin to weak late in the day due
to an approaching cold front. East southeast winds will carry warm
moist tropical air over the islands late in the day, as result
isolated to numerous showers will be possible across the northern
coast of Puerto Rico during the evening.

Friday, a col will form to the northeast of Puerto Rico as a cold
front continues to make its way closer to Puerto Rico with showers
and variable winds.

Saturday-Sunday, Currently model guidance is showing a frontal
passage Saturday or early Sunday. A prevailing east northeast wind
flow, upper level instability combined with low level moisture will
keep the islands in an unsettled pattern with showers mainly during
the morning and afternoon.

Monday-Tuesday, winds will remain out of the east northeast with
patches of low level moisture moving across the islands as the
surface and mid level ridge tries to reestablish itself over the
local area.

&&

.AVIATION...Brief MVFR conds will remain possible at JMZ/JSJ/JBQ
thought 19/22z. Elsewhere VFR conds to continue. ESE 10 to 12 kts,
becoming light and variable overnight.

&&

.MARINE...Tranquil marine conditions will continue to prevail across
the local waters during the next few days with seas below the
Small Craft criteria. Seas will increase the upcoming weekend as
a northerly swell reaches the local waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 75 88 / 20 10 20 20
STT 73 84 75 85 / 40 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
504 AM AST Tue Mar 20 2018

.SYNOPSIS...Mid to upper level ridge is forecast to build and hold
over the northeast Caribbean today through Wednesday. This will limit
any significant convection across the region. The ridge aloft is to
then erode by the latter part of the work week and into the upcoming
weekend, as a polar trough will build and spread across the western
Atlantic. This will be supported by a cold front which is expected
to approach the region by the end of the week. The associated frontal
boundary is forecast to bring an increase in low leve moisture and
allow a better chance for shower development across the islands and
coastal waters.

&&

.SHORT TERM...Today through Thursday...
A mid to upper level ridge is forecast to build over the islands
through mid-week. Low level winds will continue from the southeast
today, in response to a dissipating shear line north of the region.
TPW values will remain near the normal for March at least until
Wednesday. Although little or no shower activity is expected during
the morning, under a light southeasterly wind flow sea breezes are
expected to aid in the development of showers mainly across the
interior and northwest portion of Puerto Rico during the afternoon.
Also, shower development would remain possible downwind from the
U.S. Virgin Islands.

Winds are forecast to back from the east on Wednesday, as a surface
high pressure intensify over the Eastern Atlantic. The ridge aloft
will inhibit shower activity through much of the day, but the
available moisture will be enough to result in isolated to scattered
showers across the interior and western areas of Puerto Rico.

Thursday, the vertical stacked ridge will continue to promote fair
weather earlier on Thursday. Then, an approaching cold front with a
pre-frontal trough will combined with a warm tropical air mass to
increase the chance of shower development across the northern coast
of Puerto Rico.

.LONG TERM...Fri thru Wed...
Weakly induced surface trough will maintain a light southeasterly
wind flow across the region through Friday as a cold front will
continue to move across the western Atlantic and approach the region
from the northwest. Light southeast wind along with available moisture
convergence and diurnal effects will give way to afternoon showers
mainly over parts of the central interior and northwest sections of
PR.

By Saturday and Sunday winds are to become more east to northeast then
dominantly northeasterly Monday through Wednesday, as a surface high
pressure ridge will build and spread across the western Atlantic. Meanwhile,
the remnants of the aforementioned cold front/frontal boundary and associated
moisture field is so far forecast to sink southwards across the
region over the upcoming weekend and bring an increase in cloudiness
and shower activity.

The mid to upper level high pressure ridge is forecast to erode by Friday
and through the weekend as a polar trough will deepen and move across
the west and central Atlantic. This will create a high zonal/westerly
wind flow and provide good ventilation and instability aloft, while
eroding the trade wind cap inversion over the upcoming weekend. Therefore
for the weekend, expect the combination of the prevailing northeast
winds, upper level instability and low level moisture convergence to
keep the islands and regional waters in an unsettled weather pattern
with increasing showers especially during the early morning and afternoon
hours.

Tuesday thorough Wednesday mid to upper level ridge will build across
the southwest atlantic, while a surface high pressure is forecast to
set up north of the region. This will tighten the local pressure gradient
and thus increase the northeast trade winds resulting in occasional
patches of shallow low level moisture advection across the coastal
waters and parts of the islands. The shower activity should however
be mainly during the early morning and late afternoon hours with
mostly fair weather skies to prevail once again during the daytime
as the building ridge aloft will suppress convective development.

&&

.AVIATION...VFR conds are expected to prevail through the fcst
period. Showers and cloud are expected to form across the interior
and NW coast of PR btwn 20/16-22z. Which could bring SHRA/-SHRA and
brief MVFR conds at TJBQ and VCSH at TJMZ. Sfc winds will be calm to
light and vrb becoming from the SE at 10 kt with sea breeze
variations aft 20/14Z.

&&

.MARINE...Tranquil marine conditions will prevail across the local
waters during the next few days with seas of 2 to 5 feet and east to
southeast winds between 10 to 15 knots. Winds and seas are expected
to increase by the upcoming weekend as a surface high pressure ridge
builds north of the region and a northerly swell reaches the regional
waters and some of the local passages.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 88 75 / 10 10 20 50
STT 85 74 86 76 / 10 10 20 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
425 PM AST Tue Mar 20 2018

.SYNOPSIS...A fair and mainly stable weather pattern is expected
to prevail through Thursday with some afternoon showers developing
each day over the Cordillera Central and west sections of Puerto
Rico. The chance for shower activity will increase as a frontal
boundary moves closer to the area Friday and into the upcoming
weekend.

&&

.SHORT TERM...Tonight thru Thursday...

As expected, scattered showers developed this afternoon over the
Cordillera Central and west sections of Puerto Rico. These showers
are expected to dissipated this evening, leaving clear to partly
cloudy skies. Isolated passing showers, if any, are expected
mainly across windward areas overnight.

A mid to upper level ridge will continue to prevail across the
forecast area through at least late Thursday. This feature is
expected to quickly erode as a deep polar through moves across the
western Atlantic. Based on the latest guidance, precipitable
water will remain in the normal range through Thursday with a
sharp increase expected on Friday as a frontal boundary, which is
associated with the polar trough, moves closer to the local
islands.

Therefore, a seasonal weather pattern is expected to prevail Wed-
Thu with some afternoon showers developing each day over the
Cordillera Central and west sections of Puerto Rico. The chance
for shower activity will increase on Friday as the frontal
boundary moves closer to the area.

.LONG TERM...Fri thru Wed.../issued 504 AM AST Tue Mar 20 2018/

Weakly induced surface trough will maintain a light southeasterly
wind flow across the region through Friday as a cold front will
continue to move across the western Atlantic and approach the
region from the northwest. Light southeast wind along with
available moisture convergence and diurnal effects will give way
to afternoon showers mainly over parts of the central interior and
northwest sections of PR.

By Saturday and Sunday winds are to become more east to northeast
then dominantly northeasterly Monday through Wednesday, as a
surface high pressure ridge will build and spread across the
western Atlantic. Meanwhile, the remnants of the aforementioned
cold front/frontal boundary and associated moisture field is so
far forecast to sink southwards across the region over the
upcoming weekend and bring an increase in cloudiness and shower
activity.

The mid to upper level high pressure ridge is forecast to erode by
Friday and through the weekend as a polar trough will deepen and
move across the west and central Atlantic. This will create a high
zonal/westerly wind flow and provide good ventilation and
instability aloft, while eroding the trade wind cap inversion over
the upcoming weekend. Therefore for the weekend, expect the
combination of the prevailing northeast winds, upper level
instability and low level moisture convergence to keep the islands
and regional waters in an unsettled weather pattern with
increasing showers especially during the early morning and
afternoon hours.

Tuesday thorough Wednesday mid to upper level ridge will build
across the southwest atlantic, while a surface high pressure is
forecast to set up north of the region. This will tighten the
local pressure gradient and thus increase the northeast trade
winds resulting in occasional patches of shallow low level
moisture advection across the coastal waters and parts of the
islands. The shower activity should however be mainly during the
early morning and late afternoon hours with mostly fair weather
skies to prevail once again during the daytime as the building
ridge aloft will suppress convective development.

&&

.AVIATION...Brief MVFR conds will remain possible at JMZ & JBQ
thought 20/22z. Elsewhere VFR conds to continue. ESE 10 to 12
kts, becoming light and variable overnight.

&&

.MARINE...Tranquil marine conditions will continue to prevail
across the local waters during the next few days with seas below
the Small Craft criteria. Seas will increase the upcoming weekend
as a northerly swell reaches the local waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 88 75 87 / 10 20 50 50
STT 74 86 76 85 / 10 20 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Wed Mar 21 2018

.SYNOPSIS...Strong surface high pressure ridge across the north central
Atlantic will maintain a light to moderate east to southeast
windflow across the region through Thursday. Strong mid to upper
level ridge will also hold across the northeastern Caribbean
through Thursday.The ridge aloft will erode by Friday and into the
weekend, as a deepening polar trough will enter and move across
the western Atlantic. Surface winds are also forecast to become
more northeasterly by Friday through the weekend, as a cold front
and associated frontal boundary is expected to move across the
region, as a surface high pressure ridge builds across the
southwestern Atlantic.

&&

.SHORT TERM...Today through Friday...
As expected, mostly clear to partly cloudy skies prevailed across
the islands overnight. A few passing showers were detected across
the local waters with just a few of them moving inland over the
eastern sections of Puerto Rico and U.S. Virgin Islands.

Satellite imagery depicted an area of clouds and showers approaching
from the east. Mimic and GOES-16 TPW products indicated values
between 1.3 and 1.5 inches, which are around the normal values of
March Climatology. As this air mass approaches, passing clouds with
isolated showers are possible across the U.S. Virgin Islands and
eastern Puerto Rico during the morning hours at times. However,
rainfall amounts are expected to be less than one-tenth of an inch.
Then showers are expected to develop over the western interior and
western sections of Puerto Rico, as well as downwind from El Yunque
into the San Juan Metro area late this morning into the afternoon
hours. Elsewhere, mostly sunny to partly cloudy skies with little or
no shower activity.

A mid to upper level ridge with near normal PW values will continue
to prevail across the forecast area through at least Thursday
morning. As a result, a seasonal weather pattern will prevail
through this period.

Moisture is expected to pool over the islands by late Thursday
afternoon into the weekend as a frontal boundary (which is
associated to a polar trough) and associated surface trough move
closer to the region. The chance for shower activity and
thunderstorm development will increase after Thursday afternoon as
instability aloft, surface convergence and moisture increase across
the islands.

.LONG TERM...Sat thru Thu...Surface winds will become more east to
southeast as the cold front and associated frontal boundary is still
forecast to move across the area through the weekend. By Sunday, winds
are to become more east northeast then predominantly northeasterly
Monday through Thursday as a surface high pressure ridge will build
and spread across the western Atlantic. The remnants of the aforementioned
cold front/frontal boundary and associated moisture field is expected
to sink farther southwards. This in turn will bring a significant increase
in cloudiness and shower activity as well as better chance for thunderstorm
activity across the region.

The mid to upper level high pressure ridge is forecast to erode by over
the weekend as a polar trough deepens and moves across the west and
central Atlantic. This pattern will increase instability aloft
and provide good ventilation, while eroding the trade wind cap
inversion over the upcoming weekend. The combination of the
prevailing northeast winds, upper level instability and good low
level moisture convergence will support an unsettled weather
pattern with increasing shower activity and chance for isolated
thunderstorms across the coastal waters and local islands
especially during the early morning and afternoon hours.
Conditions are to then gradually improve by late Monday through
Thursday as a deep layered High pressure ridge builds once again
across the southwest Atlantic.

Near the end of the period expect a gradual tightening of the local
pressure gradient and thus and increase in the northeast trade winds.
As a result expect occasional patches of shallow low level moisture
advection across the coastal waters and parts of the islands. By
then the associated passing shower activity should be mainly during
the early morning and late afternoon hours with mostly fair weather
skies to prevail once again during the daytime as the building ridge
aloft will suppress convective development.

&&

.AVIATION...VFR conds are expected to prevail through the morning
hours. Passing showers and cloud are expected to affect E-PR/USVI
btwn 21/12z-18z, which could bring VCSH at TJSJ/TIST/TISX. Then
afternoon SHRA/-SHRA will develop across the interior and the W-PR
btwn 21/17-22z resulting in brief MVFR conds at TJBQ and possibly at
TJMZ. Sfc winds will be calm to light and vrb becoming from the E at
10-15 kt with sea breeze variations aft 21/14Z. Gusty winds btwn 20-
27 kts are possible.

&&

.MARINE...Overall tranquil marine conditions will prevail across
the local waters at least through Thursday with seas of 3 to 5
feet and east to southeast winds between 10 to 18 knots. Seas will
increase by the upcoming weekend, as a high pressure ridge builds
across the southwest Atlantic and a northerly swell reaches the
regional waters and some of the local passages.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 87 74 / 20 50 50 40
STT 86 76 84 75 / 30 50 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
524 AM AST Thu Mar 22 2018

.SYNOPSIS...
Showers and clouds will increase in coverage and intensity
especially across the U.S. Virgin Islands and eastern Puerto Rico
as a moist air mass approach from the east through the morning. An
induce surface trough will combine with local effect and diurnal
heating to result in showers and thunderstorms over the interior
and western sections of Puerto Rico during the afternoon hours.
The potential for shower and thunderstorm activity is forecast to
increase late tonight through the weekend, as a mid to upper
level trough breaks the trade wind cap and a surface boundary
move closer to the islands.

&&

.SHORT TERM...Today through Saturday...
Moisture is expected to continue to pool across the region as an
induced surface trough moving across the region will increase the
moisture convergence over the islands and surrounding waters
during the rest of today through Friday. A weakening cold front
and associated frontal boundary will continue to sink southwards
across the region Friday and through the upcoming weekend, along
with a deepening polar trough which will enter and move across the
west Atlantic. The trough will quickly erode the mid to upper
level ridge aloft now in place across the region over the next few
days.

Expect increasing cloudiness along a better potential for showers
and isolated thunderstorm development across the islands and coastal
waters beginning this afternoon and continuing through Friday and
Saturday when conditions are expected to deteriorate.

At this time the worst weather conditions appear to be on Friday
afternoon and Saturday as the upper level jet segment rounds the
base of the trough and move overhead allowing good divergence aloft
to combine with the low level moisture convergence and local
effects. Rainfall especially during the afternoons may be locally
heavy at times mainly over parts of the interior and northwest
sections of PR. However for today, some streamer-like afternoon
convection will be possible in and around the San Juan metro area as
well as on the downwind side of the USVI and adjacent islands.

Friday afternoon and Saturday expect increasing showers and isolated
thunderstorm development across the region due to the instability
aloft and good moisture pooling. Urban and small stream flooding
will therefore be possible over parts of north and western PR
especially on Friday and Saturday. Some of the U.S. Virgin islands
can also expect periods of isolated to scattered early morning
passing showers, followed by mostly isolated afternoon shower in the
form of streamers during the rest of the day. Increasing shower
activity and possibly isolated thunderstorms is also forecast for
parts of the USVI during the weekend, as the frontal boundary sink
farther southward across the islands. Therefore, ponding of water on
roadways and in poor drainage areas will also be possible in
isolated spots across the islands.

.LONG TERM...Sunday through Friday.
By Sunday, a frontal boundary will induce an east to northeast
wind flow across the islands. Moisture pooling will combined with
a shortwave trough, which is expected to enhance shower and
thunderstorm activity. GFS Galvez-Davidson index suggested a good
potential for this activity across the Atlantic Waters, north and
east Puerto Rico, and the northern U.S. Virgin Islands during the
night and early morning hours. Then showers and thunderstorms are
expected to move across the interior and southwestern sections
through the afternoon hours. This moist and unstable atmosphere
is expected through Monday. A surface high pressure spreading
from the west to central Atlantic will push the frontal boundary
over the islands until dissipates through around mid week. Based
on the latest model guidance, the islands will move into a wet and
unstable pattern.

A second frontal boundary is forecast to approach the islands as
a Polar trough amplified Tuesday and Wednesday. The proximity of
this deep trough will increase instability aloft and provide good
ventilation. The combination of low level convergence, favorable
upper level dynamic and plenty of tropical moisture will support
an unsettled weather pattern through at least Thursday.

By the second part of the upcoming week, model guidance are
suggesting a a gradual improvement as a vertically stacked ridge
builds once again across the region. Under this weather pattern
expect little or no shower activity with pleasant temperatures.

&&

.AVIATION...
BKN-OVC cld lyrs btw FL200-FL250...SCT ocnl BKN lyrs nr
FL020...FL040...FL100 due to passing low-mid lvl clouds with SHRA.
Few tops nr FL150 ovr coastal waters and en route btw local islandS
til 22/14z. Prevailing VFR at all terminals except for passing SHRA
vcty TNCM/TKPK/TIST/TISX/TJNR/TJSJ til 22/15z/. Aft 22/17z... Aftn
SHRA/isold TSRA mainly ovr E and W interior and NW PR with periods
of MVFR conds VCTY TJMZ/TJBQ til 22/22z DUE TO SHRA/VCTS. SFC wnds
fm E-SE 10-15 kts slightly higher and gusty with sea breeze
variations and passing SHRA.

&&

.MARINE...
Overall tranquil marine conditions will prevail across the local
with seas of 3 to 5 feet and east to southeast winds around 15
knots. A north to northwest swell is forecast to reach the islands
late Saturday into Sunday, which could increase seas between 6 and
8 feet. Marine conditions will improve Monday and Tuesday, but
seas will increase once again by mid-week of the upcoming week as
another swell invade the coastal waters.

The potential for thunderstorms is expected to increase late
tonight into at least the first part of the upcoming week across
the Atlantic Waters, especially during the night time and early
morning hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 75 86 75 / 50 40 70 60
STT 85 75 85 74 / 50 50 60 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
514 PM AST Thu Mar 22 2018

.SYNOPSIS...
Mid to high clouds moved across the islands with the
heaviest shower activity along portions of northwest and northern
Puerto Rico. Streamers did develop today but quickly collapsed
over northeast Puerto and the U.S. Virgin Islands. Low level
moisture will continue to increase over the region through the
weekend and moisten the dry layers, which will result in showers
and isolated thunderstorms through early Sunday.

&&

.SHORT TERM...Tonight through Saturday...
The short term period will be quite active with rain and isolated
thunderstorms across portions of western and northern Puerto Rico
through Saturday. Urban and small stream flooding will be be
possible over parts of north and western Puerto Rico on Friday and
Saturday. Some of the U.S. Virgin islands can also expect periods
of isolated to scattered early morning passing showers, followed
by mostly isolated afternoon shower in the form of streamers
during the rest of the day

At the low levels east southeast winds will continue to pull
deep tropical moisture over the region through Sunday. The
combination of a weak surface trough which will provide lift and,
deep tropical moisture and will result in scattered to numerous
showers across northern, central and northwest Puerto Rico through
the weekend. Saturday, the aforementioned trough will phase out
and become a weak shear line across Puerto Rico, dissipating on
Sunday.

At the mid to upper levels, the 21/12Z TJSJ sounding still shows
drier air from 750 to 300 mb. This has somewhat limited
thunderstorm growth today due to westerly winds shearing higher
clouds tops off.

Friday, the drier air begins to moisten with the only drier layer
remaining at between 600 to 300 mb. This is why showers will
become more concentrated over portions of northern, central and
northwest Puerto Rico Friday afternoon.


.LONG TERM....PREV DISCUSSION... /issued 524 AM AST Thu Mar 22 2018/
By Sunday, a frontal boundary will induce an east to northeast
wind flow across the islands. Moisture pooling will combined with
a shortwave trough, which is expected to enhance shower and
thunderstorm activity. GFS Galvez-Davidson index suggested a good
potential for this activity across the Atlantic Waters, north and
east Puerto Rico, and the northern U.S. Virgin Islands during the
night and early morning hours. Then showers and thunderstorms are
expected to move across the interior and southwestern sections
through the afternoon hours. This moist and unstable atmosphere
is expected through Monday. A surface high pressure spreading
from the west to central Atlantic will push the frontal boundary
over the islands until dissipates through around mid week. Based
on the latest model guidance, the islands will move into a wet and
unstable pattern.

A second frontal boundary is forecast to approach the islands as
a Polar trough amplified Tuesday and Wednesday. The proximity of
this deep trough will increase instability aloft and provide good
ventilation. The combination of low level convergence, favorable
upper level dynamic and plenty of tropical moisture will support
an unsettled weather pattern through at least Thursday.

By the second part of the upcoming week, model guidance are
suggesting a a gradual improvement as a vertically stacked ridge
builds once again across the region. Under this weather pattern
expect little or no shower activity with pleasant temperatures.


&&

.AVIATION...
VFR conditions will continue to prevail through the
23/00 TAF period. SHRA will decrease across northwest sections of
Puerto Rico by sunset. SFC east southeast winds 5 to 10 kt across
all TAF until 23/12Z.


&&

.MARINE...
Tranquil marine conditions across the region with seas
ranging between 3 to 5 feet, and an east southeast winds of 10 to
15 kts. A northern swell is forecast to reach the region on late
Saturday into Sunday. The northern swell will cause seas to
increase to 6 to 8 feet across most of the local water ways
starting on late Saturday.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 75 85 / 40 70 60 60
STT 75 85 74 85 / 40 60 60 60

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Fri Mar 23 2018

.SYNOPSIS...
Tropical moisture and atmospheric instability are expected to
increase through the weekend. As a result showers and
thunderstorms are expected to increase in coverage and intensity.
An induce surface trough will combine with the available
moisture, local effect and diurnal heating to result in showers
and thunderstorms over the interior and western sections of Puerto
Rico during the afternoon hours. Then, most of the activity will
move across the local waters through the overnight hours.

&&

.SHORT TERM...Today through Sunday...
Low level moisture convergence will continue to increase across
the area today through Sunday as an induced surface trough moving
through the region will increase the pooling of moisture over the
islands and surrounding waters through Saturday. A weakening cold
front/shear line and associated frontal boundary will continue to
sink southwards across the region today through the upcoming
weekend. This feature along with a deepening polar trough will
move across the west Atlantic and quickly erode the mid to upper
level ridge now in place across the region. East to southeast low
level winds will persist today, but is forecast to become more
east northeast by Saturday, then finally northeasterly on Sunday
as a surface high pressure ridge will build north of the region.

Instability aloft along with moisture convergence and local
effects, will increasing afternoon cloudiness and promote a better
potential for showers and isolated thunderstorm development across
the islands and coastal waters. This unfolding pattern will continue
through Saturday when the overall weather conditions are expected to
quickly deteriorate.

At this time, the worst weather conditions across region stills
appear to be beginning later this afternoon and continuing through
Saturday, when an upper level jet segment crosses the region while
supporting divergence aloft along with the good low level moisture
convergence and local effects. Rainfall during the afternoons will
be locally heavy at times especially over parts of the interior,
north central and northwest sections of PR ,as well as in isolated
spots on the USVI particularly on Saturday and Sunday. Isolated
afternoon convection will also be possible along the east interior
of PR where streamers may later form and affect parts of the San
Juan metro area, as well as around the adjacent islands and on the
downwind side of the USVI.

Urban and small stream flooding will therefore be possible over
parts of north,central and western PR today and on Saturday. Some of
the U.S. Virgin islands can also expect periods of isolated to
scattered early morning passing showers, followed by mostly isolated
afternoon shower in the form of streamers during the day. However,
increasing shower activity and isolated thunderstorms is also
possible for some of the USVI during the weekend, as the frontal
boundary sinks farther southward across the islands. As a result,
ponding of water on roadways and in poor drainage areas will remain
possible in isolated areas.

.LONG TERM...Monday through Saturday...
The lingering moisture, the proximity of a shear line and a jet
segment aloft would create unsettled weather conditions through
the first part of the upcoming week. GFS Galvez-Davidson index
continues to support the formation of thunderstorms across the
region through this period, especially across the Atlantic
Waters, north and east Puerto Rico, and across the U.S. Virgin
Islands during the night and early morning hours. Then, afternoon
convection is expected to affect the interior and southwestern
sections of mainland PR.

A second frontal boundary is forecast to approach the islands as
a Polar trough amplified late Tuesday into Wednesday. The
proximity of this deep trough will increase instability aloft
and provide good ventilation. The combination of low level
convergence, favorable upper level dynamic and plenty of tropical
moisture will support an unsettled weather pattern through at
least Thursday. When, FROPA was suggested around Thursday,
bringing pleasant temperatures and little or no shower activity.

Friday into the upcoming weekend, model guidance are suggesting a
a gradual improvement as a vertically stacked ridge builds once
again across the region.

Minor changes were done to the long term forecast. Except little
changes in the arrival of the expected activity for Monday through
Wednesday. Because, the latest guidance showed somewhat drier
conditions through this period.

&&

.AVIATION...
VFR conds expected at all terminals through 23/14Z. SCT ocnl BKN
cld lyrs nr FL022...FL040...FL120 with passing SHRA mainly ovr
coastal waters and btw islands til 23/14z. SHRA/Isold TSRA likely
vcty of TJMZ, TJBQ and TJPS fm 23/17z-23/23z... and ovr ATL
coastal waters. VFR elsewhere. Winds will be lgt/vrb, bcmg fm the
east with sea breeze variations at 10-15kts aft 23/13z.

&&

.MARINE...
Tranquil marine conditions expected today, seas will be 5 feet or
less through this evening. Then, seas will slowly increase at 6
feet tonight into Saturday until the arrival of a northerly swell
across the Atlantic Waters late Saturday into Sunday.

Marine conditions will improve Monday and Tuesday, but seas will
increase once again by mid-week of the upcoming week, as a long
period northerly swell is forecast to invade the coastal waters.

The proximity of a frontal boundary and good ventilation aloft
would increase the potential for thunderstorm formation,
especially across the Atlantic waters after this afternoon through
early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 86 74 / 60 60 60 50
STT 84 73 85 74 / 40 60 60 50

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
517 PM AST Fri Mar 23 2018

.SYNOPSIS...
Tropical moisture will continue to pool over the region through
Tuesday. A shearline and upper level jet will provide support for
isolated thunderstorms through late Sunday. Several Urban and
small stream flood advisories needed to be issued due to the
heavy rain over portions of southwest, western interior and
northwest Puerto Rico. The potential for urban and small stream
flooding will remain across the same areas through late Saturday.
Early next week surface ridge builds in from the west with
isolated showers possible mostly during the day.

&&

.SHORT TERM...tonight through Monday...
Low level moisture will continue to periodically move across the
region from the east. A weak front that will soon turn into a
weak shearline will remain over the local islands through late
Monday. As a result showers with isolated thunderstorms across
portions of southwest, south central Puerto on Saturday. Similar
to today expect streamers to effect the islands early in the
morning and the afternoon so other areas can also expect showers
on Saturday.

Low level winds will be east southeast through tonight,
then turning to the east northeast tomorrow. On Sunday winds will
be out of the northeast. An upper level jet segment crosses the
region while supporting divergence aloft along with the good low
level moisture convergence and local effects could cause Urban and
small stream flooding possible over parts of north, central and
western Puerto Rico on Saturday afternoon.

Sunday, a drier air mass will begin to impinge on the region late
in the afternoon but, showers will be possible over western,
southwest part of the cordillera. Troughiness at the low, mid and
upper levels will still reside over Puerto Rico and the U.S.
Virgin islands with northeast winds which will drag drier air into
the region and thwart showers activity through early Tuesday.

.LONG TERM...PREV DISCUSSION... /issued 522 AM AST Fri Mar 23 2018/
By Sunday, a frontal boundary will induce an east to northeast
wind flow across the islands. Moisture pooling will combined with
a shortwave trough, which is expected to enhance shower and
thunderstorms activity. GFS Galvez-Davidson index suggested a
good potential for this activity across the Atlantic Waters, north
and east Puerto Rico, and the northern U.S. Virgin Islands during
the night and early morning hours. Then showers and thunderstorms
are expected to move across the interior and southwestern
sections through the afternoon hours. This moist and unstable
atmosphere is expected through Monday. A surface high pressure
spreading from the west to central Atlantic will push the frontal
boundary over the islands until dissipates through around mid
week. Based on the latest model guidance, the islands will move
into a wet and unstable pattern.

A second frontal boundary is forecast to approach the islands as
a Polar trough amplified Tuesday and Wednesday. The proximity of
this deep trough will increase instability aloft and provide good
ventilation. The combination of low level convergence, favorable
upper level dynamic and plenty of tropical moisture will support
an unsettled weather pattern through at least Thursday.

By the second part of the upcoming week, model guidance are
suggesting a a gradual improvement as a vertically stacked ridge
builds once again across the region. Under this weather pattern
expect little or no shower activity with pleasant temperatures.

&&

AVIATION....VFR conds expected at all terminals overnight and
through 24/15Z. BKN sky at around FL060 will improve after 24/00Z,
then mostly cloudy skies across PR could cause CIGS at FL060 or so,
the USVI should have FEW or SKC. VCSH for TJMZ to improve after
23/23Z and only light and brief SHRA expected overnight across the
local terminals. SHRA/TSRA possible after 24/16Z, which could affect
areas near the terminals in PR.

&&

.MARINE...
Seas will increase to 5 - 6 feet on Saturday with east northeast
winds of 5 to 12 kts. A northernly swell will move into the local
waters Saturday and will remain through early Monday. A bigger
swell event is expect early next week due to a cut of low deeding
in the east Atlantic waters. A Small Craft Advisory is in effect
for the Atlantic offshore waters tonight until late Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 86 74 85 / 60 60 50 50
STT 73 85 74 84 / 60 60 50 50

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 AM AST Sat Mar 24 2018

.SYNOPSIS...A dissipating and diffuse frontal boundary/shear
line will result in periods of showers with isolated thunderstorms
through the weekend. A drier and stable air mass is expected
by mid week next week.

&&

.SHORT TERM...Today through Monday...

A dissipating and diffuse frontal boundary/shear line across the
region will continue to provide abundant low level moisture across
the local island and surrounding waters through at least Monday.
This moisture in combination with daytime heating, local effects
and the aid of an amplifying polar trough across the western
Atlantic will provide sufficient instability across the forecast
area through the forecast period. Low levels winds are expected to
turn more from the east northeast today. As a result the development
of scattered to numerous showers and isolated thunderstorms are
expected to be more prevalent across portions of central and
southwest sections of Puerto this afternoon. Rainfall will be
locally heavy at times especially over those sections of Puerto
Rico. Urban and small stream flooding will therefore be possible
this afternoon and again Sunday Afternoon. Most of the thunderstorm
activity is expected to diminish early Saturday evening, leaving
partly cloudy skies with isolated to scattered shower activity
tonight through early Sunday morning. However, for Sunday
afternoon, similar conditions are expected.

By Monday, low level moisture will begin to decrease very slowly.
However, the prevailing east northeast low level wind flow will
combine again with daytime heating and the proximity of an upper
level trough to induce again the development of shower and
thunderstorms activity over central and southwest sections of
Puerto Rico as well as across the U.S. Virgin Islands.

.LONG TERM...Tuesday through Sunday....

As a broad mid to upper level trough across the western Atlantic
shifts eastward into the central Atlantic, a ridge pattern aloft
will slowly build across the forecast area Wednesday and hold
through the upcoming weekend. Under the aforementioned building
ridge, low level moisture is expected to erode across the eastern
Caribbean.

Therefore, there is a high chance for passing showers with
isolated thunderstorms across the northern half of Puerto Rico
and the USVI Tuesday morning followed by showers and thunderstorms
developing over and south of the Cordillera Central Tuesday
afternoon. Still expect some lingering moisture on Wednesday, as
a result, expect another round of afternoon showers along the
southern slopes of Puerto Rico. Limited shower activity with
pleasant temperatures is expected Thursday onwards.

&&

.AVIATION...Mostly VFR conditions are expected across the local
flying area through 24/16Z. SHRA/TSRA will begin to develop after
24/16Z, which could affect TJBQ and TJMZ. SHRA are also possible
across the leeward, USVI, TJPS and TJSJ taf sites after 24/16Z.
Winds will be easterly up to 10 knots until 24/13z, increasing to
10- 15kt after 24/13Z with sea breeze variations.

&&

.MARINE...A northerly swell is expected to invade the local waters
later today to result in hazardous seas particularly across the
offshore Atlantic waters tonight and Sunday. Seas building 5 to 7
feet with occasional seas up to 9 feet by tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 84 75 / 40 50 50 40
STT 84 74 84 74 / 70 50 50 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
513 PM AST Sat Mar 24 2018

.SYNOPSIS...
Unsettled weather will continue through early Sunday
due to a weak boundary that will remain over Puerto Rico through
early next week. This feature will cause scattered showers and
isolated thunderstorms across portions of northern, central and
interior of Puerto Rico. A drier airmass is expected to erode
away the the moisture across the region by mid week as a result
fair weather with an occasional passing shower for Puerto Rico and
the U.S. Virgin Islands.

&&

.SHORT TERM...Tonight through Tuesday...
The diffuse tail of the shearline is still across Puerto Rico as
evidenced by the BKN/OVC layer of mid clouds (10-13 Kft)seen in the
satellite picture. This boundary is being sustained by the converging
northeast winds on the northwest side of the boundary and the east
southeast winds on the southeast side of the boundary. There will be
some give and take in the position of the boundary as the two forces
compete tonight, Sunday and Monday. On Tuesday the moisture on and
ahead of the main boundary will forge southeast. The boundary will
slowly dissipate as moisture attempts to move into the area from the
east southeast but is shunted more south of the area. However, the
net effect will be decreasing moisture after Sunday. A weak boundary
will pass through early Tuesday and late Wednesday. This will lead
to good chances for showers each day whose position will
increasingly depend of the surface winds and strength of the sea
breeze, however low level winds will remain near the surface.

.LONG TERM...Tuesday through Sunday...PREV DISCUSSION...PREV
DISCUSSION... /issued 500 AM AST Sat Mar 24 2018/

As a broad mid to upper level trough across the western Atlantic
shifts eastward into the central Atlantic, a ridge pattern aloft
will slowly build across the forecast area Wednesday and hold
through the upcoming weekend. Under the aforementioned building
ridge, low level moisture is expected to erode across the eastern
Caribbean.

Therefore, there is a high chance for passing showers with
isolated thunderstorms across the northern half of Puerto Rico
and the USVI Tuesday morning followed by showers and thunderstorms
developing over and south of the Cordillera Central Tuesday
afternoon. Still expect some lingering moisture on Wednesday, as
a result, expect another round of afternoon showers along the
southern slopes of Puerto Rico. Limited shower activity with
pleasant temperatures is expected Thursday onwards.

&&

.AVIATION...SHRA/TSRA will shift to more central portions of Puerto
Rico with mtn obscurations and MVFR/IFR conds. However TAF sites
where MVFR is psbl are limited to TJMZ. SHRA are also possible arnd
TIST/TISX. Aft 25/02Z a band of SHRA off the NW coast of PR will
apch TJBQ. Winds will increase to 10-15kt with sea/land breeze
variations. Maximum winds WSW increasing to 80 kt at FL400 by 25/12Z.


&&

.MARINE...
A northerly swell will move into the outer Atlantic waters later
today. This will create hazardous seas across the Atlantic
offshore waters tonight through Sunday. Seas will ranging from 5
to 7 feet across the outer waters, while the local water ways will
range from 4 to 6 feet with winds out east northeast 5 to 10 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 84 75 85 / 50 50 40 40
STT 74 84 74 82 / 50 50 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Sun Mar 25 2018

.SYNOPSIS...There is a chance for shower and thunder activity
across the forecast area through at least Wednesday. Expect
frequent passing showers across windward areas as well as
afternoon showers with thunderstorms developing over and south
of the Cordillera Central each day. A drier and stable air mass
is expected to encompass the area on Thursday.

&&

.SHORT TERM...Today through Tuesday...

The remnants of a frontal boundary will remain across the region
today before dissipates on Monday. Latest satellite images depicted
a layer of low to mid level cloudiness across the region in
association with the remnants boundary. This moisture in combination
with daytime heating and local effects will provide sufficient
instability across the forecast area today. Low levels winds will
continue from the northeast today. As a result the development of
scattered to numerous showers and isolated thunderstorms are
expected to be more prevalent across portions of central and
southwest sections of Puerto this afternoon. Rainfall will be
locally heavy at times especially over those sections of Puerto
Rico. Urban and small stream flooding will therefore be possible
this afternoon. Most of the shower and thunderstorm activity is
expected to diminish early Sunday evening, leaving partly cloudy
skies with isolated to scattered shower activity tonight through
early Monday morning.

The boundary remnants are expected to dissipate by Monday, resulting
in a decrease in available low level moisture across the region.
However, the east northeast low level wind flow will combine again
with daytime heating and the proximity of an upper level trough to
the west of the region to induce again the development of shower and
possible thunderstorm activity over central and southwest sections
of Puerto Rico as well as across the U.S. Virgin Islands. Model
guidance suggests that another weak frontal boundary will reach the
region late Tuesday and Wednesday, resulting in an increase in
moisture and showers across the forecast area.

.LONG TERM...Wednesday thru Monday...

As a broad mid to upper level trough across the western Atlantic
shifts eastward into the central Atlantic, a ridge pattern aloft
will slowly build across the forecast area Wednesday and hold
through Sunday. This feature is then expected to erode early next
week as trofiness develops across the western Atlantic and into
the central Caribbean. At lower levels, a surface high pressure
north of the area will yield a northeasterly wind flow much of
the forecast period.

As a result, there is a chance for shower activity Wednesday
afternoon across SW PR as moisture prevails across the eastern
caribbean. Thursday onwards, under a building ridge, limited
moisture and northeasterly winds, expect dry and stable weather
conditions with pleasant temperatures. Although mainly fair
weather will continue Sun thru Mon, locally scattered showers
across the US Virgin islands and eastern Puerto Rico are likely.

&&

.AVIATION...SHRA/TSRA across NW puerto Rico will continue to
produce brief period of MVFR across TJBQ and TJMZ through at least
25/12z. VCSH are expected elsewhere across the local flying area
until 25/16z. Winds will increase to 10 to 15 knots after 25/12z
with sea breeze variations after 25/16z. SHRA/TSRA will develop
again across central and southwest sections of PR after 25/17z,
resulting in mountains obscurations and periods of MVFR across
TJBQ and TJMZ and possible TJPS through at least 25/23z

&&

.MARINE...A northerly swell will result in hazardous seas across
the offshore Atlantic waters throughout the day but subsiding
tonight into Monday morning. Seas up to 7 feet across the Atlantic
offshore waters and subsiding 4 to 6 feet by tonight. The next
northerly swell is expected to reach the local Atlantic waters
Wednesday with seas increasing near 8 feet and occasional seas up
to 10 feet.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 75 86 75 / 50 40 40 40
STT 84 74 85 74 / 50 40 40 40

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
500 PM AST Sun Mar 25 2018

.SYNOPSIS...
Scattered showers will continue across portions of northern,
interior and southwest Puerto Rico through Monday. As a result of heavy
rainfall over the last several day Urban and small stream
flooding is possible tonight through early Monday Morning.
Remember turn around don`t drown. A front/boundary will dive south
and pass Puerto Rico on Thursday with drier air behind the
boundary. The drier will put an end to widely scattered showers
across Puerto Rico and the U.S. Virgin islands.

&&

.SHORT TERM...Tonight through Wednesday...
The shear line that has produced the showers across Puerto Rico
since Saturday night has been enhanced by upper level divergence at
the right entrance of an 80 knot jet. This shear line is still
across the Atlantic waters and is showing signs of retreating toward
the northwest. Hence showers are expected to continue over the
Atlantic waters through Monday morning. The GFS is bringing drier
air into the area from the east this evening such that relative
humidity of less than 40 percent at 850 mb should cover the
southeast half of the forecast area by 26/03Z. Moisture recovers
somewhat after 26/12Z and convection in the interior and western
portion of Puerto Rico is expected again Monday. During this time
mid layers will dry considerably as the GFS takes the boundary to
the southeast and brings in very dry air at mid levels by 26/18Z.
This will also keep any thunderstorms that develop from becoming
anything more than isolated events and only over land. Tuesday looks
a little sunnier and less showers are expected over all, but
afternoon convection will receive a little boost from heating and
light low-level wind flow. Also bubbles of upper level divergence
will pass through when upper level flow turns west. A second and
final boundary followed by modified dry air will come through late
on Wednesday and strong convergence at 250 mb should end most shower
activity except for that on the southwest portion of Puerto Rico
during the best heating of the afternoon.

&&

.LONG TERM...Wednesday thru Monday...From previous discussion
issued at 455 AM AST San Mar 265 2018...

As a broad mid to upper level trough across the western Atlantic
shifts eastward into the central Atlantic, a ridge pattern aloft
will slowly build across the forecast area Wednesday and hold
through Sunday. This feature is then expected to erode early next
week as trofiness develops across the western Atlantic and into
the central Caribbean. At lower levels, a surface high pressure
north of the area will yield a northeasterly wind flow much of
the forecast period.

As a result, there is a chance for shower activity Wednesday
afternoon across SW PR as moisture prevails across the eastern
caribbean. Thursday onwards, under a building ridge, limited
moisture and northeasterly winds, expect dry and stable weather
conditions with pleasant temperatures. Although mainly fair
weather will continue Sun thru Mon, locally scattered showers
across the US Virgin islands and eastern Puerto Rico are likely.

&&

.AVIATION...MVFR/IFR conds persisting in NW PR and over TJBQ as well
as TIST should relent BY 25/19Z but CIGS blo 050 may cont til aft
25/21Z in SHRA with mtn obscurations. Elsewhere conds VFR. Drier air
will move as far east as the ern third of PR by 26/02Z effectively
ending MVFR/SHRA. SHRA to cont over Atlantic waters for approach to
TSJU/TJBQ from NW.

&&

MARINE...A northerly swell will result in hazardous seas across
the offshore Atlantic waters tonight with seas subsiding
throughout tonight. Seas up to 7 feet across the Atlantic
offshore waters and subsiding 4 to 6 feet by tonight. The next
northerly swell is expected to reach the local Atlantic waters
Wednesday with seas increasing near 8 feet and occasional seas up
to 10 feet. The high risk of rip currents still remains along the
northern coast of Puerto Rico through Monday Night.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 86 75 85 / 40 40 40 70
STT 74 85 74 84 / 20 40 40 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
402 AM AST Mon Mar 26 2018

.SYNOPSIS...A dissipating frontal boundary will continue to result
in shower and thunderstorm activity across the forecast area today.
The frontal boundary remnants are expected to move southward,
across the Caribbean Waters by Tuesday and Wednesday, resulting
in drier and stable air across the region.

&&

.SHORT TERM...Today through Wednesday...
Cloudy skies prevailed across the forecast area with showery
conditions observed across the USVI and northeast Puerto Rico.
Temperatures were in the low to mid 70s along the coastal areas
under light and variable winds.

200mb heights will continue to fall as a broad mid to upper level
trough across the western Atlantic amplifies across the central and
eastern Caribbean. At lower levels, a surface boundary across the
central Atlantic and into the eastern Caribbean will continue to
promote moisture advection across the local isles. Although this
moisture is expected to move away by Tuesday, a second boundary is
expected to advect additional moisture on Wednesday.

Therefore,there is a high chance for showers and thunderstorms
through the forecast period. Expect passing showers across the USVI
and north and east Puerto Rico with afternoon showers and
thunderstorms developing over and south of the Cordillera each day.
These showers will result in urban flooding as well as rises along
small streams and rivers, particularly across the southwest quadrant
of Puerto Rico where the heaviest rain is expected this afternoon.

.LONG TERM...Thursday through Tuesday...
An upper level low pressure center and its associated broad mid
to upper level trough will continue to shift eastward across the
central Atlantic Thursday and Friday. As this happens, an upper
level ridge is expected to build very slowly over the region
Friday and for the rest of the forecast period. As a result
moisture is expected to erode rapidly Thursday, limiting the
shower activity across the local islands until at least Sunday.

A strong surface high pressure across the Central Atlantic will
continue to drift southeastward Thursday and Friday. This surface
high will be replaced by another strong surface high pressure that
is expected to move across the southwestern Atlantic Thursday and
Friday. This high will move just north of the region by Saturday,
maintaining a northeast low level wind flow across the local
islands until at least Sunday. Small patches of low level
moisture embedded in the northeast wind flow will reach the region
from time to time inducing periods of isolated showers over the
local islands until Sunday. However, under a building ridge, limited
moisture and northeasterly winds, expect mostly dry and stable
weather conditions with pleasant temperatures most of the period.
Winds are expected to become more eastward by Monday next week. As
a result a slight increase in moisture is expected by that time.

&&

.AVIATION...Periods of MVFR or even IFR conds in SHRA/TSRA will
remain possible at all TAF sites, particularly JMZ/JSJ/IST as a
surface front prevails across the forecast area. Easterly winds at
10 knots with some sea breeze variations throughout the day.

&&

.MARINE...A northerly swell will continue to result in seas up to
6 feet across the Atlantic waters today. The next northerly swell
is expected to reach the local Atlantic waters by Wednesday with
seas increasing up to 10 feet and occasional seas up to 11 feet.
A high risk of rip currents remains along the Northwest to
northeast beaches of Puerto Rico through early Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 83 75 / 50 50 70 70
STT 85 72 84 73 / 50 50 70 70

&&

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
402 AM AST Mon Mar 26 2018

.SYNOPSIS...A dissipating frontal boundary will continue to result
in shower and thunderstorm activity across the forecast area today.
The frontal boundary remnants are expected to move southward,
across the Caribbean Waters by Tuesday and Wednesday, resulting
in drier and stable air across the region.

&&

.SHORT TERM...Today through Wednesday...
Cloudy skies prevailed across the forecast area with showery
conditions observed across the USVI and northeast Puerto Rico.
Temperatures were in the low to mid 70s along the coastal areas
under light and variable winds.

200mb heights will continue to fall as a broad mid to upper level
trough across the western Atlantic amplifies across the central and
eastern Caribbean. At lower levels, a surface boundary across the
central Atlantic and into the eastern Caribbean will continue to
promote moisture advection across the local isles. Although this
moisture is expected to move away by Tuesday, a second boundary is
expected to advect additional moisture on Wednesday.

Therefore,there is a high chance for showers and thunderstorms
through the forecast period. Expect passing showers across the USVI
and north and east Puerto Rico with afternoon showers and
thunderstorms developing over and south of the Cordillera each day.
These showers will result in urban flooding as well as rises along
small streams and rivers, particularly across the southwest quadrant
of Puerto Rico where the heaviest rain is expected this afternoon.

.LONG TERM...Thursday through Tuesday...
An upper level low pressure center and its associated broad mid
to upper level trough will continue to shift eastward across the
central Atlantic Thursday and Friday. As this happens, an upper
level ridge is expected to build very slowly over the region
Friday and for the rest of the forecast period. As a result
moisture is expected to erode rapidly Thursday, limiting the
shower activity across the local islands until at least Sunday.

A strong surface high pressure across the Central Atlantic will
continue to drift southeastward Thursday and Friday. This surface
high will be replaced by another strong surface high pressure that
is expected to move across the southwestern Atlantic Thursday and
Friday. This high will move just north of the region by Saturday,
maintaining a northeast low level wind flow across the local
islands until at least Sunday. Small patches of low level
moisture embedded in the northeast wind flow will reach the region
from time to time inducing periods of isolated showers over the
local islands until Sunday. However, under a building ridge, limited
moisture and northeasterly winds, expect mostly dry and stable
weather conditions with pleasant temperatures most of the period.
Winds are expected to become more eastward by Monday next week. As
a result a slight increase in moisture is expected by that time.

&&

.AVIATION...Periods of MVFR or even IFR conds in SHRA/TSRA will
remain possible at all TAF sites, particularly JMZ/JSJ/IST as a
surface front prevails across the forecast area. Easterly winds at
10 knots with some sea breeze variations throughout the day.

&&

.MARINE...A northerly swell will continue to result in seas up to
6 feet across the Atlantic waters today. The next northerly swell
is expected to reach the local Atlantic waters by Wednesday with
seas increasing up to 10 feet and occasional seas up to 11 feet.
A high risk of rip currents remains along the Northwest to
northeast beaches of Puerto Rico through early Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 83 75 / 50 50 70 70
STT 85 72 84 73 / 50 50 70 70

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
448 PM AST Tue Mar 27 2018

.SYNOPSIS...

Unsettled weather will once again be possible across some areas
of Puerto Rico tomorrow due to the upper level trough and low
level moisture convergence. Thursday afternoon weather conditions
will improve as the trough move to the south and northeast of the
Puerto Rico. A mid to upper level ridge will build across the
region as result fair weather conditions with an occasional shower
through Saturday.

&&

.SHORT TERM...Tonight through Friday...

The short term will focus on the expected hazards within the next
24 hours that will occur due to the conditions listed below.

1) Conditionally unstable atmosphere at the surface, mid and
upper levels.
2) Low level moisture convergence.
3) Proximity of a weak shear line and Trough
4) upper level jet
5)Northerly swell
6) Rip current risk
7) Small craft advisory

Main messages:
- Due to heavy rainfall that occured last weekend and early this
week urban and small stream flooding is possible especially in
low line areas and poor drainage area.

-Upper and low level instability could result in frequent
lightning, brief heavy rain and strong winds of 30 mph during
the afternoon on Wednesday.

-High rip currents along the northern portions of Puerto Rico and
the U.S. Virgin Islands through Friday.

-Small craft advisory is in effect for the outer North Atlantic
waters through Thursday.

-Weather conditions will improve by midday Thursday morning.

A weak shear line will eventually weaken across Puerto Rico later
tonight or early Wednesday morning. At this time steep mid level
lapse rate has caused hazardous weather with heavy rainfall,
frequent lightning and winds greater than 30 mph. This activity
mostly occured across Ponce and vicinity, and portions of
northwest and southeast Puerto Rico. TJSJ sounding showed the low,
mid, and upper level lapse rate around 6 C/km which is
conditionally unstable.

Wednesday, unsettled weather will continue due to the trough of
low pressure approaching the outer waters of Puerto Rico this
along with the reasons listed above will cause numerous showers
with frequent lightning and strong winds. This will be possible
mostly over northeastern, central, interior portions of Puerto
Rico. Although, we can`t rule out convection developing in other
areas of Puerto Rico.

Thursday and Friday, early Thursday morning lingering moisture
will create scattered showers mostly across portions of southwest
and southeast Puerto Rico. By mid morning the front will move off
the southern coast of Puerto Rico with improving weather
conditions. A strong high pressure system will move in behind the
front and provide fair weather conditions with occasional trade
wind showers.

&&

.LONG TERM...Friday through Wednesday...PREV DISCUSSION...
/issued 444 AM AST Tue Mar 27 2018/

Upper level ridge will hold through the weekend, maintaining
relatively dry and stable atmospheric conditions across the area.
At the surface, a weak low level perturbation will approach the
northeast Caribbean by Saturday, increasing somewhat the chances
for showers. Another low level perturbation is expected on
Tuesday.

&&

.AVIATION....

TEMPOs are in place for TJPS/TJMZ due to TSRA and
MVFR ceiling. IFR conditions will be possible across these sites.
Elsewhere, passing showers and thunderstorms will continue through
at least the evening hours. Unsettled weather conditions are
expected through the forecast period. SHRA will diminish at
TJPS/TJMZ after 27/23z but TJSJ/TIST/TISX and possibly TJBQ could
expect SHRA with isol TSRA from time to time overnight.

&&

.MARINE...

Seas between 3-6 feet are expected across local waters tonight.
But, a northerly swell is will move into the local waters
Wednesday morning thus causing the local Atlantic waters, the
Mona passage and the coastal waters of western Puerto Rico to
become hazardous from Wednesday morning through Thursday
afternoon. As a result, small craft advisories will be in effect
Wednesday morning for most of the local water ways. High rip
currents risks for the northern portions of northern Puerto Rico
and most of the U.S. Virgin Islands through Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 83 74 80 / 70 70 40 20
STT 71 84 72 83 / 70 70 40 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Wed Mar 28 2018

.SYNOPSIS...Upper level low northeast of the area will linger
north of the Lesser Antilles through the end of the work week.
A surface high pressure system will build across the western
Atlantic next few days. A very dry air mass will encompass the
region Thursday and Friday.

&&

.SHORT TERM...Today through Friday...

Scattered to numerous showers are once again expected today across
portions of the local forecast area today. In the morning hours, the
highest chance of rain is across the local waters, eastern and
northern PR and the northern USVI. The remaining available moisture
will combine with the local effects and upper level trough to cause
the development of showers and isolated thunderstorms across the
interior, south and eastern sections of PR and near the northern
USVI, lesser chance but still a chance of showers and a thunderstorm
or two across the remaining sections of the local area. The showers
and thunderstorms expected today may not be as strong or numerous as
yesterday, depending on how quickly the dry air approaches. At this
time, the latest guidance still suggests that the dry air will not
arrive until late tonight, which will give enough time for showers
and thunderstorms to affect the local islands this afternoon, and
possibly cause urban and small stream flooding with rapid river
rises once again. Much better weather is expected for Thursday and
Friday as drier air and a more stable atmosphere prevails. There
will be also a nice northerly breeze which should keep maximum
daytime temps generally in the low 80s across the lower elevations
and in the 70s across the higher elevations from today through
Friday.

This weather pattern is due to a shearline over the local area which
is moving southwest and is expected to be outside of the local area
late tonight, at the same time that an upper trough over the area
will gradually move east as an upper low strengthens northeast of the
local islands. Available moisture will be near normal today, drying
up late tonight quite significantly, and remaining below normal
through at least Friday.

Marine conditions are very hazardous and more details will be described
in the marine section of the discussion.

.LONG TERM...Saturday through Thursday...

Very dry conditions are forecast to continue Saturday, before
areas of moisture associated with an upper level low affects the
local area on Sunday and Monday next week. For the beginning of
next week, a weal low level perturbation is forecast to move
across the region, increasing somewhat the chances for showers.

&&

.AVIATION...Mainly VFR conds are expected in the morning hours
across the local terminals, however, there will be showers and
thunderstorms today that will cause TEMPO MVFR conds across the
local terminals. VCSH/VCTS were put in TAF as opposed to TEMPO
groups because of uncertainty in timing, but most of the activity is
expected after 28/15Z. Winds will be from the N-NE at 10 kt early in
the morning, increasing to 15-20kt after 28/14Z with sea breeze
variations.

&&

.MARINE...Buoy 41043 located near 170 miles northeast of San Juan,
was showing increasing seas of 8 feet. Seas are expected to
rapidly increase late this morning into this afternoon as a
northerly swell invades the local waters. Small Craft and high
surf advisories are in effect. also, A high risk of rip current
is in effect.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 81 74 81 73 / 60 40 20 20
STT 85 71 83 73 / 40 40 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Thu Mar 29 2018

.SYNOPSIS...Surface high pressure across the western Atlantic will
continue to dominates the local region through at least Sunday. An
upper level low will remain northeast of the local islands
through Saturday. Drier and more stable air is beginning to make
its move southward behind the low and around the northeastern
periphery of the high.

&&

.SHORT TERM...Today through Saturday...

Much drier and stable airmass has moved into the local area.
Compared to the past few days, much better weather is expected today
and Friday as the drier and stable airmass prevails. There will be
also a nice north northeasterly breeze which should keep maximum
daytime temps generally in the low 80s across the lower elevations
and in the 70s across the higher elevations from today through
Friday and the overnight minimum temperatures will be around 70
degrees in the lower elevations and in the low to mid 60s across the
higher elevations. Saturday looks to be another day of mainly fair
weather but a small patch of moisture may briefly bring scattered
showers to the area, which could briefly affect Puerto Rico, even
though the amounts of rain are not expected to be too significant.
So overall pleasant weather expected for the next few days. However,
the marine conditions will be very hazardous, particularly today and
Friday. Please see the marine portion of the discussion and the
local marine products for more details.

.LONG TERM...Sunday through Friday...

Upper level ridge will hold throughout the forecast period. An
area of low level moisture embedded in the trade winds is forecast to
affect the local region on Tuesday next week. An increase in
shower activity is then expected. Rest of the forecast period is
expected to remain dry, with limited shower development.

&&

.AVIATION...VFR conds are expected today across the local
terminals as a dry and stable airmass dominates the area. Winds will
be from the N-NE at 10-15 kts with occasional gusts today. Sea
breeze variations are expected at TJPS.

&&

.MARINE...Buoy 41053 in San Juan is showing seas up to 9 feet
with a period of 15 seconds this morning. Hazardous marine
conditions with dangerous surf conditions will continue through
tomorrow. As a result, Small craft and high surf advisories
continue in effect. Seas between 8-10 feet are expected through
Friday night, slowly improving thereafter.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 80 72 82 75 / 20 20 20 20
STT 82 71 83 74 / 20 20 10 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
503 AM AST Fri Mar 30 2018

.SYNOPSIS...Surface high pressure across the western Atlantic will
continue to dominates the local region through at least Sunday. An
upper level low will remain northeast of the local islands
through Saturday. Drier and more stable air is beginning to make
its move southward behind the low and around the northeastern
periphery of the high.

&&

.SHORT TERM...Today through Sunday...

Drier than normal and stable airmass will prevail today across the
local area, greatly limiting the shower activity to only a few light
and brief showers that would likely leave very minimal accumulations
if any. Northeasterly winds will continue today, which should keep
maximum daytime temps generally in the low 80s across the lower
elevations and in the 70s across the higher elevations and the
overnight minimum temperatures will be around 70 degrees in the
lower elevations and in the low to mid 60s across the higher
elevations. Saturday still is expected to be another day of mainly
fair weather but scattered showers may affect the local area, which
could briefly affect Puerto Rico. Basically the same pattern that is
expected today, that of brief and light showers in the morning
hours, but Saturday should have more of such showers and maybe leave
a few hundredths of an inch of rain accumulations. Also, scattered
showers are possible across the western interior and southwestern PR
on Saturday afternoon. A change in wind direction is expected on
Sunday, which will change the locations where the brief showers
affect land areas. Even though the available moisture is expected to
be below normal for Sunday, the winds will gradually shift to an
easterly direction and the expected brief showers may affect the
eastern sections of PR and the USVI. Again, these showers possible
on Sunday are not expected to be too significant, there is simply no
upper level support for sustained and persistent showers and the
moisture is very limited.

The marine conditions will continue to be very hazardous today, even
though the local seas are gradually diminishing. Please see the
marine portion of the discussion and the local marine products for
more details.

.LONG TERM...Monday through Saturday...

For Monday, a weak low level disturbance will approach the region
from the east. As a result, an increase in cloudiness with showers
is expected to affect the local islands. For Tuesday through
Saturday, trade winds will transport patches of low level moisture
across the region.

&&

.AVIATION...VFR conds are expected today across the local
terminals as a dry and stable airmass dominates the area. Brief and
light VCSH expected at TJSJ and TIST through 30/14Z. Winds will be
from the NE at 10-15 kts with occasional gusts today, especially
after 30/14Z, diminishing wind speeds after 30/22Z. Sea breeze
variations are expected at TJPS.

&&

.MARINE...Seas will continue to subside today. Seas between 5 to 7
feet will be possible across the offshore Atlantic waters during
the first part of the day. Later, seas will diminish even more.
However, the risk of rip current will remain high through at least
Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 81 72 83 74 / 20 20 20 20
STT 83 70 85 73 / 20 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
441 PM AST Fri Mar 30 2018

.SYNOPSIS...Surface high pressure across the western Atlantic will
continue to dominates the local region through at least Sunday. An
upper level low will remain northeast of the local islands
through Sunday. Drier and more stable air will continue across the
northeast Caribbean for the next several days.

&&

.SHORT TERM...Tonight through Sunday...
An upper level low will hold to the east northeast of the local
region for the rest of the weekend. The Local islands will remain
under the subsident side of the aforementioned upper trough
tonight through Sunday. This will produce drier than normal and
stable airmass across the local area, limiting the shower
activity over the local islands. Only a few showers are possible
each afternoon mostly across southwestern sections of Puerto Rico.
However, not significant accumulations are expected.

A surface high pressure across the western Atlantic is expected to
maintain a northeasterly low level wind flow across the region
during the weekend. This wind flow will keep maximum daytime
temperatures generally in the low 80s across the lower elevations
and in the 70s across the higher elevations and the overnight
minimum temperatures will be around 70 degrees in the lower
elevations and in the low to mid 60s across the higher elevations.
Slightly higher temperatures are expected across the southern
sections of Puerto Rico due to compressional warming. A slight
increase in shower activity is expected by Saturday as a surge of
moisture moves across the region. However, not significant or
widespread precipitation is expected. Local winds are expected to
become more from the east late Sunday and early next week. Thus,
the focus of the afternoon shower will move to the western
sections of Puerto Rico with brief shower activity across eastern
sections of Puerto Rico and the US Virgin Islands, but not
significant or widespread precipitation is expected at this time.

The local seas will continue to gradually diminishing and now are
below the Small Craft Advisory Criteria. However, small craft are
urged to exercise caution across the Local Atlantic and passages.

.LONG TERM...Monday through Saturday...From previous Discussion...
For Monday, a weak low level disturbance will approach the region
from the east. As a result, an increase in cloudiness with
showers is expected to affect the local islands. For Tuesday
through Saturday, trade winds will transport patches of low level
moisture across the region.

&&

.AVIATION...VFR conds are expected to continue through the fcst
prd. The sfc winds will continue from the NE at 10 to 15 knots with
occasional gusts, diminishing below 10 kts overnight (aft 30/23z).
Passing -SHRA will move mainly in the VCTY of TJSJ/TIST and possibly
TJBQ, while mostly clear to partly cloudy skies are expected
elsewhere.

&&

.MARINE...A long period northerly swell will continue to
diminish tonight. Mariners can expect a fresh northeasterly wind
flow through at least early Sunday.

For the beach goers, the risk of rip currents continues high
across the Atlantic Beaches of PR.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 72 83 74 84 / 30 30 20 20
STT 70 85 73 84 / 0 20 20 20

[cycloneye]

Area Forecast Discussion
National Weather Service San Juan PR
452 AM AST Sat Mar 31 2018

.SYNOPSIS...Below normal moisture is still expected through
Monday, which should limit the shower activity coverage and
intensity, so only isolated to light scattered showers are
expected through Monday. The local winds will remain from the NE
through the weekend, shifting to an easterly direction on Monday
and then SE by Tuesday and Wednesday as an induced SFC trough
moves in, bringing deep moisture. Upper trough will be over
Hispaniola on Tuesday and Wednesday, which should cause enough
instability for showers and thunderstorms over the local area.

&&

.SHORT TERM...Today through Monday...

Clear to partly cloudy skies prevailed across Puerto Rico and the
U.S. Virgin Islands overnight. Some showers were noted mainly
across the Atlantic waters. Local area remains under the influence
of an upper level ridge which is maintaining relative dry weather
conditions across the local area. The northeast wind flow will
transport patches of low level moisture from time to time today.
Showers will be focus mainly across the north and northeast
sections of Puerto Rico during the morning hours, followed by
afternoon convection to develop across the southwestern sections
of Puerto Rico.

For Sunday and Monday, a relatively dry air mass will encompass
the region, limiting the shower development. After Monday, an
induced surface trough will approach the local islands from the
southeast. As a result, increasing cloudiness with showers and
possible thunderstorms are expected thereafter.

.LONG TERM...Tuesday through Sunday...

The fair weather we have been enjoying and that we expect through
Monday may come to an abrupt end on Tuesday into Wednesday as an
induced SFC trough moves in, bringing plenty of deep moisture.
This trough will combine with the deep moisture and an upper
trough over Hispaniola, which will give us plenty of instability
to help sustain showers and thunderstorms over the local islands.
Locally heavy showers and some thunderstorms are very possible if
the model guidance were to verify and this weather pattern pans
out as it appears. At this time we kept the forecast as scattered
heavy showers with isolated thunderstorms for Tuesday and
Wednesday due to only moderate confidence that everything will
line up as the long range models indicate. Having said that, if
the models continue to show consistency in the forecast, the
forecast will likely reflect the higher confidence.

For Thursday, showers and thunderstorms are also possible, but
likely due to the combination of higher than normal moisture and
the local effects since the upper trough is expected to have
moved out of the local area. Then for the following weekend, at
this time it looks like locally induced showers and thunderstorms
are possible for Puerto Rico while only isolated showers for the
USVI since an upper ridge may be over the local area by then but
moisture will be near normal and it may combine with the local
effects and diurnal heating.


&&

.AVIATION...VFR conditions will prevail across the forecast area
through at least 31/22z. Some showers can be expected in the
vicinity of TJMZ this afternoon. Low level winds will be mainly
northeast at 10 to 15 kts.


&&

.MARINE...Seas continue to diminish and at this time we are
expecting seas of up to 6 feet. Winds will be up to 15 knots from
the NE today. There is still a high risk of rip currents from the
northwest to the northeast beaches of Puerto Rico today. Many of
the remaining beaches have a moderate risk of rip currents which
include eastern and western PR, Vieques and Culebra islands, the
eastern half of Saint Croix and the north and western beaches of
Saint Thomas.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 74 85 75 / 30 20 20 20
STT 84 71 84 72 / 20 20 20 20