Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 281401
Area Forecast Discussion
National Weather Service San Juan PR
1001 AM AST THU JUL 28 2016
Mostly fair weather with mostly clear to partly cloudy skies
prevailed across the local islands this morning. A few passing
trade wind showers have been detected mainly across the local
waters with only a few of them briefly affecting the US Virgin
Islands and eastern coastal areas of Puerto Rico. So far, no
significant rainfall accumulation occured inland throughout the
morning hours. As the day progresses, an increase in moisture
in association with an approaching upper level trough, is expected
to aid in shower and thunderstorm development across the waters
and across the interior and western portions of Puerto Rico this
afternoon. Showers and possible thunderstorms could also affect
the metropolitan area of San Juan. Some flood advisories can be
expected this afternoon for these areas.
Mostly VFR cond thru the rest of the forecast period. SHRA/TSRA
with mtn obscuration expected across interior and western
portions of PR from 16Z-22Z, possibly affecting TJMZ and TJBQ.
SHRA/VCTS possible for TJSJ and TJPS. Low level winds mainly from
the east at 10-15 kts with higher gusts and sea breeze variations.
There is a moderate risk of rip currents for some of the northern
coasts of Puerto Rico. Seas up to 4 feet and winds up to 15 kts
expected to continue. Hazardous marine conditions possible in and
near strong showers and thunderstorms.
.PREV DISCUSSION... /issued 524 AM AST THU JUL 28 2016/
SYNOPSIS...A surface high pressure will continue to dominates
the local region through Saturday night. An upper level trough
will move across the area today. An active tropical wave will
affect the local area Sunday and Monday. Saharan Air Layer will
encompass the region after the wave.
DISCUSSION...Passing showers were seen across the coastal waters
overnight. Some of these showers affected the local islands...but
rainfall accumulation were minimal. This increase in moisture is
associated with an approaching upper level trough which is located
northeast of the U.S. Virgin Islands. Although this trough is not
strong enough...will aid in the development of showers and
thunderstorms mainly over the western interior and west section of
An active tropical wave...currently located in the central
Atlantic it is expected to approach the local area by Sunday. At
this time...models agreed on the timing of the wave but disagree
somewhat on the strength of the wave. The ECMWF model forecast a
stronger wave affecting the local area...compared to the GFS. The
most important thing it is that both models agreed on active
weather beginning on Sunday morning and continuing through Monday
morning. We will continue to closely monitor the evolution of this
wave next few days. Stay tuned.
AVIATION...Mostly VFR conditions with a Saharan air layer could
slightly reduce VIS at the local terminals but still expected to be
P6SM during the next 24 hours. For this morning, VCSH and brief SHRA
possible over the Leewards, USVI and TJSJ TAF sites. Easterly winds
to increase to around 10-15 KT and gusty after 28/13Z prevailing
from the E with sea breeze variations. SHRA/TSRA expected to develop
over PR after 28/16Z with mountain obscurations. VCTS/TSRA likely to
affect areas in and around TJPS and TJMZ, VCSH/SHRA at TJBQ.
MARINE...Tranquil marine conditions are expected to continue
through at least Saturday. Seas up to 4 feet and winds up to 15
knots are expected.
.PRELIMINARY POINT TEMPS/POPS...
SJU 91 79 89 80 / 20 30 30 20
STT 90 79 89 81 / 40 30 30 20