Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 252033

Area Forecast Discussion
National Weather Service San Juan PR
433 PM AST Sun Jun 25 2017

.SYNOPSIS...An overall dry and stable air mass prevailed across
much of the region today with little or no shower activity observed
across the region. The exception was over the west interior of Puerto
Rico where showers and an isolated thunderstorms developed and produced
brief periods of moderate to locally heavy rainfall. This activity however
was of short duration. A tropical wave continued to cross the eastern
Caribbean with associated moisture spreading westward along the leading
edge now just south of the U.S. Virgin Islands.


.SHORT of today through Tuesday...

Moisture associated with the tropical wave will continue to spread
west and north across the region overnight through early Monday
as this wave will quickly move westward and exit the region by
Monday afternoon. This moisture advection should favor the development
of additional showers and thunderstorms across the Caribbean Waters
and portions of the U.S. Virgin Islands and eastern PR. In the wake
of the tropical wave, a drier air mass associated with an extensive
area of Saharan dust will spread over the region by Monday afternoon
and continue through Tuesday. This drier airmass is then expected
to encompass the region and limit shower activity.

.LONG TERM...Wednesday through Monday...

Overall dry and somewhat hazy conditions are expected to prevail across
the islands at least through Wednesday, with shower and thunderstorm
development limited to mainly across the west sections of Puerto Rico
during the afternoons. Elsewhere, mostly fair weather skies and somewhat
hazy conditions should prevail.

Moisture is expected to quickly increase across the forecast area once
again on Thursday and through the remainder of next week as another
easterly disturbance will arrive and spread across the region area.
Recent model guidance all continue to suggest a fairly moist and unstable
environment will persist across the region at least into the weekend.
Therefore the potential will remain high for shower and thunderstorm
development across the regional waters and local islands at least during
the latter part of next week. Passing late evening and early morning
showers should affect the windward areas, followed by locally and diurnally
induced convection across the interior and west sections of Puerto Rico
during the afternoon. Some of this activity will also be enhanced due
to the proximity of a developing Tutt low Thursday through Friday.


.AVIATION...VFR conditions will prevail across most of the TAF sites
expect TJBQ and TJMZ where MVFR are possible in SHRA/TSRA thru 22Z.
SHRA/TSRA associated with a tropical wave will move into the flying
area this evening. Most of the TSRA activity will remain over the
Caribbean Waters...however brief SHRA may affect the Leeward Islands
and USVI at times. VFR conds will return by 26/18Z. Low level winds
will be mainly east southeast at 10 to 15 kts.


.MARINE...Mariners can expect overall seas of 3-5 ft, and prevailing
easterly winds of 15-20 knots across most of the coastal waters and
local passages overnight through Monday. This will create choppy
seas. A tropical wave moving across the eastern Caribbean overnight
through Monday will also increase the chance for isolated thunderstorms
mainly across the Caribbean waters. This will also create hazardous
sea conditions mainly across the offshore coastal waters.


SJU  79  89  79  90 /  40  40   0  30
STT  79  89  79  90 /  50  50  10  30




LONG TERM....RAM is the U.S. government's official web portal to all federal, state and local government web resources and services.