Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 200122
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
922 PM AST Mon Feb 19 2018

.UPDATE...Isolated and brief showers were observed late int he
afternoon with a bit more scattered showers in the evening across
northern PR. Variably cloudy skies with isolated to scattered
brief showers are expected overnight across the Atlantic waters,
northern USVI and north and eastern PR. The rainfall
accumulations are expected to be minimal as these showers are
moving quickly. Available moisture is expected to remain low on
Tuesday so the chance of measurable rain is expected to be low.

&&

.AVIATION...VFR conds expected through the local terminals for the
next 24 hours. VCSH possible but the SHRA are moving quickly so
they should be brief over any one point. Winds will be mainly from
the ENE overnight at 10-15KT and gusty, increasing up to 20KT
after 20/13Z with gusts up to 30KT. Some sea breeze variation
could be observed at TJPS after 20/14Z, turning winds a bit more
from the SE.

&&

.MARINE...Seas are now hazardous with seas that could reach 10
feet tonight across the offshore Atlantic and Caribbean waters as
well as the Mona Passage. Seas up to 8 feet elsewhere except the
coastal waters SW of PR where seas will be up to 5 feet. Seas will
increase after midweek as winds increase even more. There is a
high risk of rip currents across most of the local beaches of PR
and the USVI, except for western PR.

&&

.PREV DISCUSSION... /issued 440 PM AST Mon Feb 19 2018/

SYNOPSIS...High pressure building in the western Atlantic will
sink slowly south during the week while weakening only slowly
generating fresh to strong breezes across the area.

SHORT TERM...Tonight through Wednesday. Partly sunny skies with
breeze conditions prevailed across Puerto Rico and the U.S. Virgin
Islands today. Very light passing showers were observed. Winds
between 20 to 25 mph were observed across some localized area,
mainly in higher elevations. Strong surface high pressure is the
responsible for these weather conditions. A very dry air mass has
encompassed the region. As a result, limited shower activity is
expected through at least Wednesday. An increase in low level
moisture is expected on Wednesday.

LONG TERM...Thursday through Monday...(Previous discussion)

Pronounced northeast to east northeast low level flow will begin
to subside by mid week but will still be moderate to fresh by
Sunday. A weak cold front will usher in cooler and relatively
drier air Wednesday night through Thursday night. Patches of
moisture and weak, rumpled remnants of fronts will pass through
for the rest of the period insuring that brief scattered showers
keep windward slopes damp Friday through next Monday. A weak upper
level low will pinch off the trough extending toward the area at
250 mb on Thursday to enhance some of the showers that will occur.
When it lifts north it will bring an 85 knot jet of southwest
winds across the area, but generally flow will be subsident on
this side of the low until late in the weekend.

AVIATION...VFR conds are expected to prevail through the forecast
cycle with brief -SHRA/SHRA possible at the Leeward and USVI
terminals as well as JSJ/JBQ. ENE winds 15-25 knots with higher
gusts, becoming at around 12-15 knots overnight.

MARINE...Local buoy were showing an increase in seas with buoy
41053 located around 170 nautical miles northeast of San Juan
indicating near 7 feet. Seas are expected to remain hazardous for
the rest of the week. Small Craft advisories continue in effect.

FIRE WEATHER...Latest surface observations indicated relative
humidity values at Camp Santiago drop to 39% late this afternoon.
Although relative humidity values will remain near threshold level
tonight, winds are expected to decrease across the southern
plains.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  72  81  73  81 /  30  30  30  40
STT  71  85  71  83 /  30  30  30  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Wednesday morning for Central
     Interior-Culebra-Mayaguez and Vicinity-North Central-
     Northeast-Northwest-Ponce and Vicinity-San Juan and
     Vicinity-Southeast-Southwest-Vieques-Western Interior.

     Small Craft Advisory from 8 AM Wednesday to 6 PM AST Thursday
     for Southeast.

VI...High Rip Current Risk through Wednesday morning for St Croix.

     Small Craft Advisory until 6 PM AST Friday for St.Thomas...St.
     John...and Adjacent Islands.

AM...High Rip Current Risk through Wednesday morning for Coastal
     Waters OF Southwestern Puerto Rico out 10 NM-Coastal Waters
     of Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 6 PM AST Thursday for Coastal Waters
     of Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 6 PM AST Friday 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 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.

&&

$$

SHORT TERM...JA
LONG TERM....FC


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