Area Forecast Discussion
Issued by NWS San Juan, PR

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204
FXCA62 TJSJ 172038
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
438 PM AST Sat Feb 17 2018

.SYNOPSIS...Surface high pressure continues to the north of the
local islands, causing moderate east to east northeast winds
across the local area. The local pressure gradient will tighten
early in the workweek as a stronger surface high pressure
develops across the northwestern Atlantic.

&&

.SHORT TERM...Tonight through Monday...Partly cloudy skies
prevailed across Puerto Rico and the U.S. Virgin Islands today. An
area of cloudiness moved across the area, with little
precipitation observed. Latest satelite images depicted a dry air
mass encompassing the region from the east. This dry air mass will
result in less shower activity. Partly cloudy to clear skies are
expected tonight into Sunday morning. A patch of low level
moisture embedded in the trade winds is expected to reach the
local area Sunday morning. Strong high pressure will build across
the region late sunday into Monday, maintaining relatively dry
weather conditions across the islands.

.LONG TERM....LONG TERM...Tuesday through Sunday...(previous
discussion)

Patches of moisture will pass through at times, causing brief
showers over the local area. These showers will mainly be observed
across the local waters, USVI, Vieques and Culebra as well as
northern and eastern PR, especially during the nighttime and early
morning hours. A strong SFC high pressure across the northwestern
Atlantic will cause the local pressure gradient to tighten early
in the workweek, which will cause windy conditions locally. These
winds will likely inhibit the usual sea breeze convergence in the
afternoon hours across western PR, which means that the areas that
could be affected by rain will probably be the local islands and
north and eastern PR, even during the daytime hours. Wednesday
looks to be the day with the best moisture so it is the day, in
the long term range of the forecast, that will likely observe the
best rainfall coverage, however, it is still expected to be
somewhat windy so the showers observe should be very brief. No
major change in the overall pattern is expected other than maybe
the wind speeds decreasing by Thursday.

&&

.AVIATION...A dry air mass will limit SHRA across the islands, but
Winds btwn 10 and 20 kt will push clouds and trade wind showers at
times mainly across TIST/TJSJ. SHRAs due to diurnal effects are
expected across the SW quadrant of PR resulting in VCSH at
TJMZ/TJPS. SCT-BKN cld lyrs nr FL025...FL050...FL080. Expect
easterly winds at 10-20 kt with gusts in/near SHRA. Winds are
expected to drop around 10 kt overnight.

&&

.MARINE...Seas have diminshed to around 6 feet across the local
waters.However, hazardous marine conditions are expected to
continue through at least mid next week. Seas will increase once
again late Sunday night. As a result, small craft advisories will
be in effect. Winds up to 20 knots are also expected.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  72  84  74  83 /  30  30  30  20
STT  72  84  72  84 /  30  30  30  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 PM AST this evening for Northeast-
     San Juan and Vicinity-Southeast.

     Small Craft Advisory from 8 PM Sunday to 8 AM AST Wednesday for
     Southeast.

     High Rip Current Risk through Sunday evening for North Central-
     Northwest-Western Interior.

VI...Small Craft Advisory from 8 PM Sunday to 8 AM AST Wednesday for
     St.Thomas...St. John...and Adjacent Islands.

AM...Small Craft Advisory from 8 PM Sunday to 8 AM AST Wednesday for
     Anegada Passage Southward to 17N-Atlantic Waters of Puerto
     Rico and USVI from 10 NM to 19.5N-Caribbean Waters of
     Puerto Rico from 10 NM to 17N-Coastal Waters of Northern
     Puerto Rico out 10 NM-Coastal Waters of Northern USVI and
     Culebra out 10 NM-Coastal Waters of Southern Puerto Rico
     out 10 NM-Coastal Waters of Southern USVI Vieques and
     Eastern Puerto Rico out 10 NM-Mona Passage Southward to 17N.

&&

$$

SHORT TERM...CAM
LONG TERM....FC



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