Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 221513

Area Forecast Discussion
National Weather Service San Juan PR
1113 AM AST Sun Oct 22 2017

.UPDATE...Some brief trade wind showers affected portions of
Eastern PR during the early morning hours with accumulations of
less than a tenth of an inch observed. Mostly fair weather
conditions will continue to prevail across the region throughout
the day as dry air at the mid to upper levels will continue to
restrict rainfall activity. Locally and diurnally induced showers,
however, may still develop across portions of western PR during
the afternoon hours. The aformentioned dry air, however, will
cause these showers to be short-lived with no significant
accumulations expected.


.AVIATION...Mostly VFR conditions will prevail across all
terminals during the entire forecast period. Brief reductions to
MVFR conditions may occur near or over TJBQ and TJMZ due to
possible SHRA fm 22/16z to 22/22z. E-SE winds of 10-15KT with sea
breeze variations through this afternoon. Winds diminishing below
10KT after 23/00z.


.MARINE...Seas up to 5 feet with winds up to 15 knots across the
Atlantic waters. Choppier conditions across the Caribbean waters
with seas up to 6 feet and winds up to 20 knots, therefore, small
craft operators are urged to exercise caution. Low to moderate
rip current risk across all the local beaches.


.PREV DISCUSSION... /issued 412 AM AST Sun Oct 22 2017/

SYNOPSIS...Upper level ridge will continue as the main weather
feature across the region until at least Monday. This feature will
continue to produce a relatively dry and stable weather pattern
across the forecast area. An upper trough northeast of the region is
expected to sink southward over the Lesser Antilles by midweek
increasing the moisture across the local islands.

SHORT TERM...Today through Monday...
Isolated passing showers during the early morning hours mostly
along the east coastal sections of the islands. Mostly fair
weather skies expected across Puerto Rico and the U.S. Virgin
Islands during the rest of the day with limited shower development
expected across the forecast area. Shower activity if any should
focused along parts of the interior and west sections of Puerto
Rico with mostly sunny and fair weather skies elsewhere. Previous
TJSJ 22/00Z upper air sounding as well as the Satellite derived
precipitable water products both suggest continued dry and stable
airmass to persist through Monday except for occasional patches of
trade wind moisture which may lead to periods of early morning
and afternoon shower activity of short duration over parts of the
islands. No significant weather feature or impacts are anticipated
at this time.

LONG TERM...Tuesday through
An upper level low/trough northeast of the region is expected to
sink southward toward the Leeward Antilles on Tuesday and
Wednesday. This feature will result in a gradual increase in
moisture across the region by midweek. However, at this moment
not significant or widespread precipitation is expected.
A tropical wave is expected to reach the region Friday generating
a better chance of showers and thunderstorms through next

AVIATION...Prevailing VFR conds at all terminals durg entire prd.
Few-Sct cld lyrs FL025-FL035. Isold SHRA en route btw islands. Mstly
CLR ovr much of land areas except for few passing SHRA along E
coastal sections of islands til 22/12z. Isold-Sct SHRA fm 22/16z-
22/22z ovr ctrl mtn range of PR and VCSH NR TJMZ. SFC wnds Lgt and
vrb bcmg fm E-SE  10 to 15 kts w/ocnl higher gust along coastal
areas aft 22/14z-22/23z.

MARINE...Seas up to 6 feet and winds up to 20 knots will continue
across the surrounding waters through early in the week. Small
Craft are urged to exercise caution across most of the coastal
waters. A low to moderate risk of rip currents is expected to
remain across most of the local beaches.


SJU  89  77  87  75 /  20  20  20  20
STT  88  77  87  76 /  20  20  20  30




LONG TERM....JA is the U.S. government's official web portal to all federal, state and local government web resources and services.