Area forecast discussion
National Weather Service San Juan PR
1035 PM AST Sat may 18 2013
Update...afternoon showers that affected the interior and western
sections of PR dissipated around sunset...leaving mostly clear to
partly cloudy skies. Satellite imagery shows a line of high clouds
moving in but little to no low clouds. In addition...terminal
Doppler radar does not show precipitation over the area. Relatively
dry air is expected to continue moving in tonight into Sunday
morning...keeping things fairly quiet overnight.
Available moisture is expected to gradually increase on Sunday
into Monday. Moderate to locally heavy showers and isolated
thunderstorms are once again possible across portions of the
interior and western Puerto Rico on Sunday afternoon...with a few
showers elsewhere...most likely due to streamers off the islands
and El Yunque Rain Forest.
The current forecast package is consistent with the latest
guidance and observations...therefore no significant changes were
made to the forecast package.
&&
Aviation...VFR conds will prevail all areas until around
19/16z. Showers/thunderstorms and rain will develop after 19/16z and create general
mountain obscurations in western PR MVFR/locally IFR in rain showers and low ceilings.
Also come MVFR may be seen at tist between 19/17-22z due to cloud
streamers off upwind islands. Winds aloft east-east-southeast 5-15 knots up through 12
kft. Maximum winds westerly 60 knots between 40-48 kft.
&&
Marine...smal craft should exercise caution due to winds of up to
19 knots. Seas are expected to remain at 5 feet or less. This
general pattern in marine conditions is expected for the next few days.
&&
Previous discussion... /issued 247 PM AST Sat may 18 2013/
Synopsis...short wave trough is expected to reach Puerto Rico
and the U.S. Virgin Islands on Monday. Local pressure gradient
will continue to tighten as surface high builds and relocates
to the north of the forecast area. A broad middle to upper level
trough is expected to extend across the western Atlantic into
the central Caribbean early next work week.
Discussion...as expected...skies were mostly sunny across Puerto
Rico...Culebra and Vieques early this morning...becoming partly
to variably cloudy during the late morning and afternoon hours.
Across the U.S. Virgin Islands...partly cloudy skies prevailed
throughout the day. Terminal Doppler radar as well as satellite
imagery indicated limited shower activity so far.
A generally fair weather pattern will continue to prevail across
the forecast area at least through middle week...with passing showers
across the east coastal sections of the islands during the morning
hours...followed by afternoon convection which will be mainly
focused across western Puerto Rico. By middle week...a broad trough
is forecast to extend from the western Atlantic into the central
Caribbean...with divergent side of associated jet over the area.
This will bring enough moisture and favorable upper level dynamics
over Puerto Rico and U.S. Virgin Islands to result in a better
chance of shower and thunderstorm activity.
Aviation...MVFR conds will remain possible through 18/21z along
the Cordillera Central and at tjmz in areas of shra/tsra. Mountain tops
may be obscured over western interior of PR. For the northern leeward
and USVI islands...mainly VFR conds are expected.
Marine...tranquil seas expected to prevail for the next several
days...with seas up to 5 feet. Easterly trade winds will continue
to gradually increase as local pressure gradient tightens.
&&
Preliminary point temps/pops...
sju 77 87 77 86 / 10 20 20 20
stt 76 87 76 87 / 20 20 20 20
&&
Sju watches/warnings/advisories...
PR...none.
Vi...none.
Coastal waters...none.
&&
$$
12/25
