Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 260455 AAA
AFDSJU

Area Forecast Discussion...UPDATED
National Weather Service San Juan PR
1255 AM AST Sun Jan 26 2020

.UPDATE...Light rain persists over much of western Puerto Rico and
will only slowly dissipate. Zones were updated to reflect the
wetter forecast. Flooding is not expected, but saturated soils may
become unstable in steep terrain.

&&

.AVIATION...Periods of MVFR conds may be encountered around PR
TAF sites TJSJ/TJPS until aft 26/10Z. Mtn obscurations. Sfc winds
remain light and less than 5 knots except over Caribbean waters
near heavier showers.

&&

.MARINE...No changes to the marine discussion.


&&

.PREV DISCUSSION... /issued 902 PM AST Sat Jan 25 2020/

UPDATE...Moderate to heavy showers developed across southwestern
portions of Puerto Rico shortly after 7 PM, affecting mainly the
municipalities of Yauco and Guanica. Localized amounts of up to
1.5 inches have fallen across Guanica according to doppler radar
estimates. Additional showers are also affecting portions of
northeastern Puerto Rico, including the San Juan metro area. These
showers are expected to continue across these areas during the
next couple of hours with improving weather conditions expected
overnight. An increase in shower activity is expected on Sunday
afternoon as the low-level moisture associated with the remnants
of a cold front move over the area. Showers are expected to first
develop across portions of interior Puerto Rico and then extend
into portions of northern and southern Puerto Rico during the
late afternoon and early evening hours. The steering flow will
continue to remain very light, therefore, the showers that
develop will be slow-movers once again and pose a risk for some
urban and small stream flooding in areas that receive the
heaviest activity. Showers are also expected to increase in
coverage across the USVI, with the best chance expected during the
afternoon and evening hours.

AVIATION...Mainly VFR conditions expected through 26/16z. Sct
SHRA across northeastern PR will result in VCSH mainly across
TJSJ. Sct SHRA activity is expected to develop across the local
area after 26/16z, affecting mainly TJSJ/TJPS/TJMZ and the USVI
terminals. TEMPO MVFR conditions are possible. Winds are expected
to be light and variable through the period with sea breeze
variations developing after 26/14z.

MARINE...Hazardous seas of up to 7 feet are expected to continue
through the overnight period, gradually diminishing to below 6
feet on Sunday as the northerly swell diminishes across the
Atlantic waters and local passages. A high risk of rip currents
continues for the north-facing beaches of Puerto Rico, Culebra,
Vieques, and Saint Thomas during the overnight period.

PREV DISCUSSION... /issued 140 PM AST Sat Jan 25 2020/

SYNOPSIS...
Rainfall activity is expected in the afternoon hours across the
interior and northeastern sections of Puerto Rico due to low
level moisture associated with the remnants of the previous
front. This moisture in combination with the local effects will
continue to help in the development of showers through the next
workweek. A northerly swell is causing hazardous seas up to 8
feet across the Atlantic waters and local passages through
Sunday.

SHORT TERM...Today through Monday...

Low-level moisture associated with the cold front located just
southeast of the region in combination with the local and diurnal
effects will result in showers across the interior and northwestern
section of Puerto Rico. Those showers are expected to stay more
time over the same area due to a steering wind flow very weak
today. For that reason, we can expected generous amounts of rain
over sections of Puerto Rico but only minor amounts to the U.S.
Virgin Islands. On Sunday, at upper levels a patch of moisture
will move north into the region. In combination with low-level
moisture associated with the remnants of the front will enhance
the showers activity and cloudiness. The development of these
showers are expected across interior, south central and eastern
Puerto Rico. For the U.S. Virgin Islands, some isolated to
scattered showers are expected. winds are forecast to remain
gentle for Sunday through Monday and will result in showers
activity more longer over the same area

LONG TERM...Tuesday through Sunday...
The long term period start with a wind flow from south-southeast
this will enhanced the low-level moisture across the region at
least until Thursday. These low-level moisture in combination with
the local and diurnal effects will result in scattered to
isolated showers. Winds are forecast to remain between lights to
gentle leading slow moving showers during this period. There is
just a slight thunderstorm threat, but the potential will again be
there for localized areas of flooding where the most persistent
showers set up. Areas affected by recent earthquakes will still be
susceptible to these forecasted showers. Friday looks to be a
transition day, as the flow at low to mid levels will switch to
northerly as a front passes to our north. Drier conditions are
forecasted to prevail behind the front, and this is suggested by
both the American and European models which adds to our confidence
in this forecast.

AVIATION...
A frontal boundary lingering near the region
will produce cloudiness and showers across the islands. Clouds are
expected to develops over the interior of PR and USVI through the
afternoon. SHRA will concentrate mainly over the vicinity of St
Thomas, and the interior, north and east Puerto Rico btwn 25/18-
26/02z. Another round of SHRA/+SHRA will develop after 26/15z over
PR/USVI. Light and VRB winds will continue with localized sea breeze
variations and some gusty winds near showers.

MARINE...
Hazardous marine conditions will continue across the Atlantic Waters
and Caribbean Passages through at least Sunday. Mariners can expect
seas up to 8 feet with occasional seas up to 10 feet across the
Atlantic waters, Mona and Anegada Passages. For the Caribbean
waters, tranquil marine conditions are expected for the next several
days with seas up to 5 feet with occasionally seas up to 6 feet.
Also, winds will continue mainly light and variable.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  73  83  74  85 /  40  60  40  40
STT  72  82  73  82 /  50  70  70  40

&&

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

VI...High Rip Current Risk through this afternoon for St.Thomas...St.
     John...and Adjacent Islands.

AM...Small Craft Advisory until 8 AM AST this morning for Atlantic
     Waters of Puerto Rico and USVI from 10 NM to 19.5N-Coastal
     Waters OF Northwestern Puerto Rico out 10 NM-Coastal Waters
     of Northern Puerto Rico out 10 NM-Mona Passage Southward to
     17N.

     Small Craft Advisory until 2 AM AST early this morning for
     Coastal Waters OF Southwestern Puerto Rico out 10 NM-
     Coastal Waters of Northern USVI and Culebra out 10 NM.

&&

$$

SHORT TERM...WS
LONG TERM....MB
PUBLIC DESK...99


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