Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 250149
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
949 PM AST Sat Feb 24 2018

.UPDATE...An isolated thunderstorm with numerous showers developed
this evening over the Mona Passage just south of Mona Island. This
activity was aided by a TUTT near the Dominican Republic. Trade
wind showers continued over the local Atlantic waters and the
waters from eastern PR to the Anegada Passage, with a few
affecting portions of the islands as they streamed westward. For
the rest of the overnight hours...same pattern of trade wind
showers are expected to prevail with some enhancement by the
meandering TUTT to the northwest of the region. On Sunday, better
moisture content is forecast to move across the region and showers
will be heavy at times with thunderstorm development once again
possible over portions of the interior and southwestern PR and
during the evening hours over the western waters of PR.


&&


.AVIATION...Mainly VFR conds expected to prevail during the next
24 hours across all terminals. However, trade wind SHRA could
result in tempo MVFR across the Leeward/USVI and eastern PR
terminals through Sunday morning. Latest 25/00z indicated E-ENE
winds between 8-21 kts below FL100.


&&

.MARINE...Seas will continue to subside through Sunday and all
small craft advisories will expire by Sunday afternoon across all
regional waters. However a long period northeast swell will
increase seas once again by midweek next week. Moderate trades
around 10-15 kt will prevail from the east to northeast during the
next several days.

A high risk of rip currents will continue on Sunday across the
northern beaches of PR, Culebra and St. Croix.


&&

.PREV DISCUSSION... /issued 429 PM AST Sat Feb 24 2018/

SYNOPSIS...Surface high pressure will hold across the western
Atlantic just north of the area while weakening over the rest of
weekend and into early next week. As a result winds will continue
to diminish and hazardous marine conditions to subside. An upper
level trough will linger west of the region over Hispaniola and
Jamaica until early in the week. This will result in favorable
conditions for the development of showers across the local
islands.

SHORT TERM...Tonight through Monday...
Latest radar observations as well as satellite images depicted
scattered showers across the Atlantic waters moving from time to
time across the local islands. This activity will continue to
affect mostly the U.S. Virgin Islands, Vieques, Culebra as well
the northern and eastern sections of Puerto Rico tonight and
Sunday morning with brief periods of moderate to locally heavy
rain possible. As a result some areas may observe ponding of
water along roads and poorly drained areas. Showers and possible a
couple of thunderstorms are also expected to develop across the
interior and western sections of Puerto Rico Sunday and Monday
Afternoon.

A surface high pressure will hold across the western Atlantic
north of region while weakening until early next week. This
feature is expected to maintain an east to east northeast low
level wind flow across the region for the next several days.
At the same time, a mid to upper level trough and a subtropical
Jet is expected to linger close to the region in a favorable
position for the development of showers and possible thunderstorms
until at least Monday. A drying trend is expected across the
forecast area starting on Tuesday.

LONG TERM...Tuesday through Sunday...
Surface high pressure will fade in the western Atlantic just
north of the local area by Tuesday, but will be replaced by a
second high moving out of the eastern United States Wednesday
through Thursday with continued brief shower activity across the
local islands. A mid level ridge is forecast to build across the
southwestern Atlantic by mid next week and hold through at least
the end of the work week. This will limit shower activity area-
wide. Therefore, very stable atmospheric conditions are forecast
to prevail across the region during the long term period.

AVIATION...SCT-BKN cld lyrs nr FL025..FL050...FL090 durg prd with
passing SHRA at TJSJ/TIST/TISX/TJBQ and en route btw PR and Nrn
Leeward islands. Slight chance of Isld TSRA VCTY TJMZ/TJPS til
24/22z with TEMPO MVFR psbl in SHRA. SFC winds fm ENE 15-20 knots,
with OCNL higher gusts til 24/23z. L/lvl winds ENE btw 20-30 kts blo
FL200...bcmg fm SW incr w/ht ABV...MAX Wnd 80-100 kts NE of PR btw
FL300-FL350.

MARINE...Local buoys were indicating seas between 6-8 feet at around
9 seconds period this afternoon. Seas will continue to decrease
tonight through the rest of weekend. For those reasons, the high
surf advisory was cancelled but rough breaking wave action will
continue to result in life threatening rip currents along the
northern exposed beaches of PR and portions of the smaller islands
through the rest of weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  81  72  81  72 /  60  60  60  70
STT  82  71  82  72 /  60  60  60  70

&&

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

     High Rip Current Risk until 6 AM AST Sunday for Mayaguez and
     Vicinity.

VI...High Rip Current Risk through Sunday afternoon for St Croix.

     Small Craft Advisory until 8 AM AST Sunday for St.Thomas...St.
     John...and Adjacent Islands.

AM...Small Craft Advisory until 8 AM AST Sunday for Caribbean Waters
     of Puerto Rico from 10 NM to 17N-Coastal Waters of Northern
     USVI and Culebra out 10 NM-Coastal Waters of Southern USVI
     Vieques and Eastern Puerto Rico out 10 NM.

     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-Coastal Waters of Northern Puerto Rico
     out 10 NM-Mona Passage Southward to 17N.

     Small Craft Advisory until 2 AM AST Sunday for Coastal Waters OF
     Northwestern Puerto Rico out 10 NM.

&&

$$

SHORT TERM...DS
LONG TERM....JF


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