Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 232004

Area Forecast Discussion
National Weather Service San Juan PR
404 PM AST Tue May 23 2017

.SYNOPSIS...So far only few showers were detected over the west
interior of Puerto Rico. Mostly sunny, hot and hazy conditions
prevailed elsewhere. The fairly dry air mass with suspended
Saharan dust particulates is expected to persist and affect the
forecast through the end of the week. An upper level ridge is
forecast to build across the islands,therefore, fair weather
conditions, warm temperatures and little or no shower activity
will continue through the end of the work week.


.SHORT TERM...Rest of today through Thursday...
Model guidance suggests that Saharan Air Layer is expected to
linger across the region for the next several days, but lesser
concentration is expected by Thursday. Overall sunny and hazy
skies with warmer than normal temperatures are expected to prevail
across most of the region.

A strong mid level ridge will remain in place and limit convective
development, however, a short wave is expected to quickly move across
the region on Wednesday and reach the lesser antilles by Thursday.
This feature along with limited moisture availability, strong daytime
heating, sea breeze convergence and local forcing should aid in
the development of showers and possibly an isolated thunderstorm
on Wednesday afternoon. Lesser activity expected on Thursday. The
shower activity should be focused over the central interior, western
and northwest Puerto Rico each day. Little or no significant rainfall
is expected over the adjacent islands including the U.S. Virgin Islands
at this time as conditions are forecast to remain fairly dry.

.LONG TERM...Friday through Wednesday...
Mid to upper level upper level ridge will remain the main weather
feature across the northeast Caribbean through Saturday. An upper
level low and an associated trough is forecast to develop and linger
just east of the region through the upcoming weekend. The upper trough
axis is also forecast to remain east of the region maintaining the
islands on the subsidence side of the trough. Surface high pressure
across the central Atlantic is expected to maintain moderate easterly
trade winds across the region. Model guidance suggests that the Saharan
Air Layer will persist over the area through most of the weekend
resulting in hazy and a relatively dry airmass. However, a tropical
wave will move westward across the tropical Atlantic and approach to
the Lesser Antilles by Monday.It is then forecast to move over the
eastern Caribbean Tuesday through Wednesday. This feature should bring
an increase in tropical moisture transport and consequently increase
the chance for showers and thunderstorms over the local islands and
surrounding waters. Stay tuned.


.AVIATION...VFR conds will prevail across all TAF sites. A Saharan
air layer will persist across the region, but vis is not expected
to decrease below 6SM. Although VFR conds expected, SHRA cannot be
ruled out across the NW quadrant of PR with VCSH at TJMZ/TJBQ til
23/22z. SKC durg overnight with ISOLD -SHRA en route from the Leeward
Islands and USVI. Sfc winds mainly southeast at 10-15 kts with higher
gusts. Winds are expected at 10 knots or less aft 23/23z.


.MARINE...High pressure building north of the region will aid in
slightly increasing the trade winds across the surrounding waters,
resulting in posible seas building up to 6 feet across the Atlantic
waters and local passages through Wednesday. Marine conditions will
then gradually improve through the weekend when seas subsiding to
4 feet or less across most of the waters.


SJU  80  92  79  90 /  10  10  10  20
STT  81  88  79  87 /  20  10  10  20




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