Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 241447
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1047 AM AST SUN JUL 24 2016

.UPDATE...Some passing showers were observed across the local
area...mainly over the coastal waters. Passing showers will
continue to affect the region from time to time the rest of this
morning...with some showers and possible isolated thunderstorms
expected to develop over the western interior and northwest sections
of Puerto Rico. No changes were made to forecast grids this
morning.

&&

.AVIATION...Mainly VFR conditions are expected to prevail, however,
passing trade wind showers could reach the Leeward, USVI and eastern
PR terminals thru the fcst period. Streamers are expected to develop
by mid to late morning across the USVI, resulting in periods of -RA
at times and SCT cigs between FL025-FL070. SHRA/TSRA will develop
over the interior and western PR with areas of mtn obscurations
between 16Z-22z, resulting in TEMPO MVFR conditions at TJBQ/TJMZ.
Also, SHRA can affect at times TJSJ during the afternoon hours.


&&

.MARINE...No changes to previous discussion.


&&

.PREV DISCUSSION... /issued 511 AM AST SUN JUL 24 2016/

SYNOPSIS...An upper level trough/TUTT west of Puerto Rico is
enhancing the instability across Puerto Rico and the U.S. Virgin
Islands. Another surge of moisture associated with a tropical wave
is expected on Tuesday. Drier and more stable pattern will return
to the islands by midweek. Then...Another TUTT will be positioned
over the region between Thursday and Friday bringing once again
unstable conditions.

DISCUSSION...Satellite Precipitable Water Analysis shows an area
of deep moisture associated with an induced trough over the Northeast
Caribbean Region. This high moisture content will combine with the
instability aloft to support scattered to numerous showers across
the local waters and portions of the islands today. Although...
most of the showers will remain over the local waters this morning...
some showers will move inland over the eastern third of Puerto Rico
the rest of the morning. Stronger showers and isolated thunderstorms
are expected over portions of the Cordillera Central and parts of
the North and West Puerto Rico this afternoon. The U.S. Virgin
Islands will experience scattered showers at times.

Slightly drier pattern is anticipated on Monday as the TUTT moves
over the Central and Wrst Caribbean. However...scattered showers
remain in the forecast...especially across western Puerto Rico
during the afternoon hours. Operational models indicate deep
moisture associated with a tropical wave reaching the local
region on Tuesday. This will result in another round of showers
and thunderstorms across the local area. Generally stable pattern
is forecast by midweek as a drier air mass with Saharan Dust will
reach the local islands.

Unstable conditions will likely return to the islands at the end
of the work week as another upper trough/TUTT will move over the
islands. Therefore...expect another round of showers and thunderstorms.

AVIATION...Mainly VFR conditions are expected to prevail, however,
passing trade wind showers could reach the Leeward, USVI and eastern
PR terminals thru the fcst period. Streamers are expected to develop
by mid to late morning across the USVI, resulting in periods of -RA
at times and SCT cigs between FL025-FL070. SHRA/TSRA will develop
over the interior and western PR with areas of mtn obscurations
between 16Z-22z, resulting in TEMPO MVFR conditions at TJBQ/TJMZ.
Also, SHRA can affect at times TJSJ during the afternoon hours. Low
level winds prevail E-ESE at 10-20 knots with sea breeze variations
after 14Z.

MARINE...Typical seas are forecast across the local waters. Mariners
can expect seas of 3-5 feet and winds around 10-20 knots over the
next several days. Small craft operators should exercise due to
winds up to 20 knots across the coastal waters of Northern Puerto
Rico. However...no Small Craft Advisories are anticipated over
the next 5-7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  77  87  79 /  40  30  20  50
STT  88  78  89  79 /  50  30  20  50

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

71/72



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