National Weather Service San Juan PR
508 AM AST Wed May 10 2017
.SYNOPSIS...
An upper level trough meandering aloft will combine with abundant
low level moisture enhancing showers and thunderstorm activity
through at least late Thursday. A mid to upper level ridge is
expected to build over the region by Saturday into next week. At
the surface, troughs will move across the islands the next few
days. A surface high pressure over the central Atlantic will
maintain an east to east southeast wind flow across the northeast
Caribbean for the next few days.
&&
SHORT TERM...Today through Friday...
The broad band of moisture from an old frontal boundary has moved
into the Leeward islands and will stall there today. This has caused
mid and upper level clouds to clear--at least temporarily--and will
provide additional heating for the activation of shower and
thunderstorms around midday across much of western and interior
Puerto Rico. Southeast flow at the surface will cause showers to
again favor the northwest portion of the island. Although a short
wave has passed through the area and caused good convection,
thunderstorms and some flooding, we are still in the broad base of
the upper level trough that will continue to generate very favorable
conditions today and tomorrow. On Friday upper level support ends
and we are on the back edge of the moisture at mid levels, this will
limit the convection that will be favored by strong heating.
Although showers will continue through the period, the most intense
showers and thunderstorms are expected today and another round of
heavy rain may trigger some river flooding and areas of urban and
small stream flooding which will exasperate the situation of already
saturated and unstable soils to create mudslides. Therefore a flash
flood watch will be issued for the period from noon today to 6 PM
AST today.
.LONG TERM...Saturday trough Wednesday...
A ridge aloft is expected to build over the region by the upcoming
weekend into next week. However, model guidance quickly bring a
tropical wave with abundant tropical moisture across the region
Sunday or Monday. This scenario can increase the potential for
showers and thunderstorms across the islands. Moisture is forecast
to rapidly decrease Tuesday into mid week. The lingering moisture
will result in periods of showers and thunderstorms during the
afternoons and early evening hours due to the combination of
daytime heating and local effects mainly along the Cordillera and
western sections of Puerto Rico. The U.S. Virgin Islands, as well
as the windward sections of PR, can expect passing showers mainly
during the overnight and early morning hours each day.
&&
.AVIATION...
Isold SHRA will continue across eastern PR and
local waters to the north through 10/14Z. Aft 09/16Z afternoon
SHRA/TSRA developing across PR, but mainly wrn and interior, will
cause mtn obscurations and VCSH/VCTS at TJBQ, TJMZ, TJPS, and
possibly TJSJ between 09/17Z and 04/23Z. TEMPO MVFR conds possible
at TJBQ/TJMZ between 09/18Z and 04/21Z. Winds will be mainly from
the ESE at 5-15KT with sea breezes developing after 04/14Z. Max
winds west 50-70 kts at FL410-470 incrg thru 11/12z.
&&
.MARINE...
Mariners can expect seas between 2 and 5 feet across the region,
but are urged to exercise caution across the Anegada Passage and
the U.S. Virgin Islands surrounding waters due to winds between
15 to 20 knots. Elsewhere expect east to east southeast winds
between 10 and 15 knots. Seas expected to continue at less than 5
feet for the next several days. A trof pattern will enhance
showers and thunderstorms formation across the coastal waters.
Therefore, mariners and beach goers should be alert and monitor
the local marine products as weather conditions can deteriorate
quickly over the waters and coastal areas.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 86 76 / 50 30 30 20
STT 84 76 85 75 / 50 40 40 30
&&