Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 222011
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
411 PM AST Thu Feb 22 2018

.SYNOPSIS...Strong surface high pressure over the western
Atlantic just north of the region will continue to result in
breezy conditions across the region through at least Friday.
Trade wind shower pattern will continue to bring areas of showers
across the USVI and the northern sections of PR each day. Upper
level trough and associated jet maxima will move over the region
Friday through Saturday. This will increase the chances of showers
across the region.

&&

.SHORT TERM...Tonight through Saturday...
Terminal Doppler radar indicated isolated to scattered passing
showers moving southwestward from the Atlantic waters, affecting
mostly the U.S. Virgin Islands, Vieques, Culebra as well the
northern and eastern sections of Puerto Rico. This activity is
expected to continue tonight. However, rainfall amounts have been
minimal if any. The remnants of a weak frontal boundary will
continue to dissipate across the Caribbean waters just south of
the region. Strong surface high pressure will hold across the
western Atlantic through at least Tuesday, next week. An upper
level trough extends southwest from an upper level low across the
central Atlantic, several hundred miles to our north and is
accompanied on its southern periphery by a strengthening jet. This
jet will cross the area from the southeast Friday into Saturday
morning bringing strong upper winds over the region. The strong
surface high pressure across the western Atlantic will continue to
bring patches of low level moisture across the local islands for
the nest several days. This moisture will combine with the strong
upper level winds and upper trough to allow shower activity to
increase Friday and Saturday. There is also a possibility of
thunderstorms developing over Puerto Rico Friday and Saturday.
Although the showers in the thunderstorms could be heavy flooding
is not expected due to the rapid movement the showers. In summary,
showers will continue across the windward slopes of Puerto Rico
and at least the northern U.S. Virgin Islands tonight and increase
through Friday night aided by the trough and jet just mentioned.
Showers should also be forced across most of Puerto Rico north of
the Cordillera Central in the moderate to fresh trade winds that
will persist through at least Saturday.

.LONG TERM...Sunday through Thursday...from previous discussion...
High pressure north of the region will hold through Tuesday
maintaining a moderate to locally fresh east to northeast trade
wind flow across the area. Trade wind showers will continue to
move and increase in frequency during the first part of next week.
Meanwhile, upper level trough over the central Caribbean will
continue to aid in the development of showers with possible
thunderstorm development through Tuesday. Urban and small stream
flooding in isolated areas will be possible with the heaviest
showers during the long term period.

&&

.AVIATION...VFR conds are expected to prevail through the forecast
cycle with VCSH at the Leeward and USVI terminals as well as
JSJ/JBQ. ENE winds 15-20 knots with higher gusts, becoming at around
10-12 knots overnight.

&&

.MARINE...Rough seas continue across the regional waters except
in the coastal southwestern waters of PR. Seas will range between
8-12 feet and east to northeast trades at 15-25 knots will
continue across the region. Winds will gradually decrease through
the weekend as well as the seas. However, SCA are in effect
through the weekend due to seas still reaching 7-8 feet. High
surf advisory continues for the northern beaches of PR and the
USVI through Friday afternoon. High risk of rip currents will
continue through the weekend across the northern beaches of the
islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  82  73  81 /  70  70  60  60
STT  72  82  72  83 /  60  50  40  30

&&

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

     High Surf Advisory until 6 PM AST Friday for Culebra-North
     Central-Northeast-Northwest-San Juan and Vicinity-Southeast-
     Western Interior.

     Wind Advisory until 6 PM AST this evening for Culebra-Mayaguez
     and Vicinity-North Central-Northeast-Northwest-San Juan and
     Vicinity-Southeast-Vieques-Western Interior.

     High Rip Current Risk through late Friday night for Central
     Interior-Southeast.

     Small Craft Advisory until 8 PM AST Friday for Southeast.

VI...High Rip Current Risk through Saturday afternoon for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     High Surf Advisory until 6 PM AST Friday for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     Wind Advisory until 6 PM AST this evening for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     Small Craft Advisory until 8 PM AST Friday for St.Thomas...St.
     John...and Adjacent Islands.

AM...High Rip Current Risk through Saturday afternoon for Coastal
     Waters of Northern USVI and Culebra out 10 NM-Coastal
     Waters of Southern USVI Vieques and Eastern Puerto Rico out
     10 NM.

     High Surf Advisory until 6 PM AST Friday for Coastal Waters of
     Northern USVI and Culebra out 10 NM-Coastal Waters of
     Southern USVI Vieques and Eastern Puerto Rico out 10 NM.

     Wind Advisory until 6 PM AST this evening for Coastal Waters of
     Northern USVI and Culebra out 10 NM-Coastal Waters of
     Southern USVI Vieques and Eastern Puerto Rico out 10 NM.

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

     Small Craft Advisory until 8 PM AST Friday for Coastal Waters of
     Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 6 PM AST Saturday for Caribbean
     Waters of Puerto Rico from 10 NM to 17N-Coastal Waters OF
     Northwestern Puerto Rico out 10 NM-Coastal Waters of
     Northern Puerto Rico out 10 NM-Coastal Waters of Northern
     USVI and Culebra out 10 NM-Coastal Waters of Southern USVI
     Vieques and Eastern Puerto Rico out 10 NM-Mona Passage
     Southward to 17N.

     Small Craft Advisory until 2 PM AST Sunday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N.

&&

$$

SHORT TERM...JA
LONG TERM....JF
AVIATION...JA


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