Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 202026
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
426 PM AST Fri Apr 20 2018

.SYNOPSIS...Broad surface high pressure will continue across the
eastern Atlantic through early next week. Patches of moisture
embedded in the trades will move occasionally across the region
for the next several days, inducing the development of showers and
thunderstorms each afternoon across interior and western Puerto
Rico with isolated to scattered showers across the U.S. Virgin
Islands and eastern Puerto Rico during the nights and early
morning hours.

&&

.SHORT TERM...Tonight through Sunday...
A patch of moisture embedded in the trades moved across the U.S.
Virgin Islands, Vieques, Culebra as well as across the eastern
sections of Puerto Rico this morning inducing the development of
scattered to numerous passing showers over those sectors. This
moisture in combination with daytime heating and local effects
will continue to produce showers and thunderstorms over western
and interior sections of Puerto Rico until late this afternoon.

Drier air will continue to move across the region tonight and
Saturday. However...patches of moisture embedded in the trades
will move occasionally across the region during the next several
days. This moisture will induce the development of isolated to
scattered showers across the U.S. Virgin Islands, Vieques, Culebra
as well as across the eastern sections of Puerto Rico during the
night and early morning hours followed by scattered showers and
isolated thunderstorms across western and interior sections of
Puerto Rico each afternoon. Latest satellites images depicted
another patch of moisture to the east of the region. This feature
is expected to produce scattered showers tonight and early
Saturday morning across the local waters, USVI and eastern PR.
By Sunday, drier air is expected to dominate the region. Not
significant changes are expected in the present weather pattern
during the forecast period.

.LONG TERM...Monday through Friday...From previous reasoning...
Moisture peaks on Monday and Tuesday and an upper level trough
will support thunderstorm development each day. But overall the
same weather pattern is expected to prevail each day. Shower and
thunderstorm development is expected to develop each afternoon
over portions of western Puerto Rico. Trade wind showers will
persist across the USVI and eastern portions of PR during the
overnight and early morning hours. Drier air is expected to move
once again from the east by Friday. Day time maximum temperatures
are expected to reach the high 80s to low 90s across the lower
elevations and overnight minimum temperatures are expected to
range from the low 60s across the higher elevations to low 70s
along the lower elevations.

&&

.AVIATION...Periods of MVFR conds likely in and around JMZ/JBQ and
possibly JSJ in SHRA/TSRA through 20/22z. Expect VCSH at the Leeward
and USVI terminals this afternoon and early tonight. ESE winds
around 10-15 knots with some sea breeze variations, becoming at 10
knots or less overnight.

&&

.MARINE...A long period northeast swell will continue to result
in life threatening rip currents across the north, east and
southeast facing beaches of Puerto Rico, Culebra, Vieques and St.
Croix. Small craft advisories are in effect for the offshore
waters and passages due to seas up to 7 feet. East winds will
continue at 15 to 20 knots across the region through the weekend.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  86  75  87 /  40  40  20  10
STT  76  85  75  87 /  40  20  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for Central Interior-
     Culebra-North Central-Northeast-Northwest-San Juan and
     Vicinity-Southeast-Vieques-Western Interior.

VI...High Rip Current Risk through late Saturday night for St Croix.

AM...High Rip Current Risk through late tonight for Coastal Waters of
     Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 PM AST this evening for Anegada
     Passage Southward to 17N-Caribbean Waters of Puerto Rico
     from 10 NM to 17N-Mona Passage Southward to 17N.

     Small Craft Advisory until 6 PM AST Saturday for Atlantic Waters
     of Puerto Rico and USVI from 10 NM to 19.5N.

&&

$$

SHORT TERM...WS
LONG TERM....JF



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