National Weather Service San Juan PR
430 AM AST Sun May 14 2023
.SYNOPSIS...Showers and thunderstorms are expected to develop
across western areas of Puerto Rico as well as portions of the
San Juan metro area this afternoon. A similar weather pattern is
expected to prevail much of the upcoming workweek due to available
moisture, diurnal heating and local effects. The risk for urban
and small stream flooding, heat indices in the upper 90 degrees
to the low 100s, and low to moderate risk of rip currents
continues.
&&
.SHORT TERM...Today through Tuesday...
The overall pattern is for today to be slightly less active than
yesterday, followed by an overall drier day tomorrow. The wettest
day of the short term period is likely to be Tuesday.
Patchy moisture is pushing into the region from the east and
southeast this morning. Precipitable water values will remain
generally within seasonally typical values over the region. This
will help to sustain a typical shower pattern, overall. The steering
flow is generally southeasterly, though there is quite a bit of
shear above around 700 hPa, with winds becoming more southerly then
west-southwesterly. This could result in showers being over some of
north central Puerto Rico again today, though overall the pattern
indicates that the peak in activity will be over northwestern and
interior Puerto Rico. Streamer development is also likely in the
east again today.
Tomorrow, a dry slot is expected to move over part of the region,
including southern and western portions. This will inhibit,
somewhat, the shower activity over the region. However, moisture
levels are likely to only dip to around the lower end of normal, so
some shower activity is still likely. Additionally, an upper-level
jet is expected to be over the region on Monday, resulting in a
modest increase in instability. Because of this, Monday is still
likely to see active weather, though it could be the driest day of
the period.
For Tuesday, moisture will increase. The overall steering flow will
be slower than previous days, as the high pressure over the central
Atlantic will weaken and be pushed eastward by an approaching
surface trough. This will result in moisture convergence over the
islands through the day on Tuesday. Model guidance is more bullish
on an upper-level trough that is expected to pass by the region to
the northwest than it has been in previous days. Because of this,
there is less certainty in the forecast, but this does suggest the
potential for some troughing at around 250 hPa just west of the
islands on Tuesday. If this does verify, Tuesday would also bring an
increase in instability alongside the increase in moisture. Because
of this, it is likely that Tuesday will bring enhanced shower
activity. The steering flow is also forecast to become a bit more
southerly overall through the afternoon, which could push the peak
in shower activity eastward to over most of northern Puerto Rico.
&&
.LONG TERM...Wednesday through Monday...
A mid to upper level ridge pattern is expected to prevail across
the forecast area Thu-Fri, as the aforementioned trofiness at
around 250 hPa dissipates north of the forecast area early in the
cycle. Nevertheless, the ridge pattern aloft will be short-lived
with the 250 hPa heights falling once again Saturday into the rest
of the upcoming weekend. At lower levels, a surface high pressure
located across the northeast Atlantic will continue to yield east
to east southeast winds. This will promote moisture advection and
precipitable water values near or above seasonal levels much of
the week.
Under this evolving pattern, locally induced afternoon showers and
thunderstorms are expected across western areas of Puerto Rico each
day. The risk for urban and small stream flooding, mudslides in
areas of steep terrain, as well as water surges along rivers will
be elevated. Daytime temperatures across Puerto Rico and the U.S.
Virgin Islands will remain in the mid to upper 80s and low 90s
along the coastal areas and in the mid 80s across the central
portions. Heat indices will stay in the upper 90 degrees to the
low 100s along the coastal areas of the islands.
Based on the latest guidance, the wettest day in the long term
forecast is likely to be Wednesday.
&&
.AVIATION...Generally VFR conds expected next 24 hours for most
aerodromes. Passing SHRA cont over the waters thru morning; SHRA
near TIST/TISX/TJSJ likely to have little to no operational
impacts at terminals. Afternoon SHRA/TSRA expected for interior
and W/NW/N PR. Streamer dvlpmnt off of terrain likely in E, incl
San Juan streamer. Greatest risk of impacts is for TJBQ, followed
by TJSJ; cannot rule out brief MVFR or worse, esp for TJBQ.
Passing SHRA return tonight.
&&
.MARINE...Mariners should expect seas between 3 to 5 feet, with
occasional seas up to 6 feet. Showers with isolated thunderstorms
are expected each afternoon at the coastal areas of western and
northwestern Puerto Rico. Choppy seas could be locally hazardous
in and around thunderstorms. Winds will be from the SE at 10 to 15
knots, with higher gusts near thunderstorms. There is a moderate
risk of rip currents along the north and east facing beaches of
Puerto Rico and Culebra.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&
$$
SHORT TERM...CRS
LONG TERM....OM
AVIATION...CRS