Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 230813
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
413 AM AST Tue May 23 2017

.SYNOPSIS...Mostly fair and stable weather conditions with high
concentrations of saharan dust particulates will continue across
the region for the next several days. A surface high across the
central Atlantic will maintain an easterly trade wind flow across
the region for most of the forecast period. A wetter pattern is
possible early next week as a tropical wave moves across the
region.

&&

.SHORT TERM...Today through Thursday...
Partly cloudy skies prevailed across Puerto Rico and the U.S. Virgin
Islands overnight. Doppler radar detected some light passing showers
mainly across the local waters. Some light passing showers can be
expected this morning, but overall dry and hazy conditions are
expected to prevail.

Model guidance suggests that Saharan Air Layer is expected to
continue affecting the local region today. This will maintain hazy
skies and warmer than normal temperatures across the region for the
next several days. However, residual moisture will combine with
strong daytime heating, sea breeze convergence and mountains lifting
to induce a new round of showers and possible thunderstorms over
central interior, western and northwest Puerto Rico each afternoon.
Significant precipitation is not expected to affect the U.S. Virgin
Islands.

.LONG TERM...Friday through Wednesday...
An upper level ridge will remain as the main weather feature
across the northeast Caribbean until at least Saturday. An upper
level low and an associated upper level trough is expected to
develop just to the east northeast of the region by the upcoming
weekend, eroding the upper ridge. However, the upper trough axis is
expected to remain to the east of the region maintaining the
local islands under the subsidence side of the trough. A Surface
high pressure across the central Atlantic is expected to produce a
moderate easterly trade winds across the region. Model guidance
also continue to indicated that a Saharan Air Layer will persist
over the area through most of the forecast period resulting in
hazy, relatively dry and stable airmass over the northeast
Caribbean into the upcoming weekend. A tropical wave along 40 West
this morning will continue to move westward approaching to the
Lesser Antilles on Monday an moving over the eastern Caribbean on
Tuesday and across the local islands late Tuesday and Wednesday.
This feature will result in an increase in cloudiness, showers and
thunderstorms over the local islands and surrounding waters late
in the forecast period.

&&

.AVIATION...VFR conditions will prevail across all TAF sites through
at least 23/16z. VCSH can be expected across TJMZ and TJBQ with
mountain obscurations. Low level winds will be mainly southeast at
10 to 15 kts with higher gusts.

&&

.MARINE...High pressure over the Central Atlantic will increase
the trade winds across the surrounding waters, resulting in
posible seas building up to 6 feet across the Atlantic Waters by
midweek. Marine conditions will then gradually improve through the
weekend when seas subsiding to 2-4 feet across most of the
waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  80  90  80 /  20  10  10  20
STT  89  80  90  80 /  20  10  10  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...FC
LONG TERM....JF



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