Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 222115

Area Forecast Discussion
National Weather Service San Juan PR
515 PM AST Wed Nov 22 2017

.SYNOPSIS...A surge of low level moisture is expected on Thursday
and Friday. Drier conditions return later in the weekend. Mid to
upper level ridge will continue to hold for the next several days.
A short wave trof moves close to the area by mid week next week.


.SHORT TERM...Thursday through Saturday...

Precipitable water content will be at normal to above normal
levels(~1.75 inches) on Thursday and Friday as moisture increases
from the east with the trade winds. Therefore, expect showers
with a chance for isolated thunderstorms to develop mainly over
the Cordillera Central into the western interior portions of the
islands. Elsewhere, partly cloudy skies with passing showers are
expected from time to time. Fair weather conditions return during
the weekend as drier air filters once again and PWAT content drops
to below normal levels.

.LONG TERM...FROM PREVIOUS DISCUSSION....Sunday through Friday...

The high pressure at 700 mb forming north of us Thursday and
Friday will move northeast and shear out on Sunday due to an
approaching cold front. Areas of drier air will pass through on
Sunday before moisture again begins to increase Monday and Monday
night over us ahead of the front. The front will stall out
northwest of the area Tuesday through Thursday. During the
interaction of weak local troughs moving in the easterly low level
flow toward the front, moisture increases and scattered showers
begin to affect much of Puerto Rico and the U.S. Virgin Islands.
Low pressure at lower levels develops north of Hispaniola later
next week in response to a short wave that dives southeast during
the week and crosses the area on Wednesday causing a low to cut-
off north of the forecast area. This and an upper level jet around
the short wave and subsequent cut-off low will also enhance
showers in only modestly moist east to east southeast low-level
flow continuing across the area through the end of next week.


.AVIATION...VFR conds across the local flying durg prd. Few SHRA
ovr coastal waters btw islands fm22/23z-23/14z. Sfc wnd bcmg lgt/vrb
aft 22/23z...bcmg fm E 10-15 kts aft 23/14z with sea breeze
variations. L/lvl wnds fm SE 5-15 kts blo FL100...then bcm fm SW-W
and incr w/ht ABV. No sig wx impacts anticipated across the flying
area attm.


.MARINE...Small craft advisory in effect for the offshore
Atlantic waters due to 7 ft seas from tonight through Thursday.
Small crafts should exercise caution across the coastal waters of
eastern Puerto Rico and the USVI as well across the Anegada
passage due to seas up to 6 feet. A moderate risk of rip currents
continues for much of the north and east facing beaches of the


SJU  77  86  77  88 /  30  50  50  50
STT  76  86  77  87 /  50  50  50  50


PR...Flash Flood Watch through Thursday afternoon for Northwest-
     Western Interior.

AM...Small Craft Advisory from 8 PM this evening to 2 PM AST Thursday
     for Atlantic Waters of Puerto Rico and USVI from 10 NM to



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