034
FXCA62 TJSJ 232042
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
442 PM AST Sat Nov 23 2024

.SYNOPSIS...
Unsettled weather is expected to prevail, with increasing showers
and thunderstorms. This will maintain the risk of flooding
elevated in some areas. Marine and coastal conditions will
deteriorate this week as another northerly swell arrives.

&&

.SHORT TERM...Tonight trough Monday...

Variable weather conditions persisted in the morning hours, with
some brief showers across southeastern sections of Puerto Rico and
mostly partly cloudy skies across the rest of the islands. Shower
activity starts in the afternoon, affecting mainly the north-central
areas with rainfall estimates between one to two inches. Daytime
temperatures were in the mid to upper 80s, with some isolated
areas in the low 90s across the coastal areas and much cooler across
the mountains.

Tonight, variable weather conditions will persist as moisture
from the Caribbean continues to move across the region and a deep
polar trough continues to deep across the northwestern Caribbean.
For Sunday, the islands will be under the same pattern; at the
surface, winds will turn more from the east-southeast, and
moisture from a surface perturbation, now over the lesser
Antilles, will increase the potential to observe shower activity
across northeast Puerto Rico and the U.S. Virgin Islands in the
morning hours. In the afternoon hours, the Galvez-Davison Index
indicate the potential for stronger convection, with thunderstorm
development likely.

On Monday, surface winds will be backing from the east in
response to the interaction with the frontal boundary and the
surface ridge dominating over the western Atlantic. Although
moisture will be reduced on Monday, shower activity is expected
across the interior and west of Puerto Rico.

.LONG TERM...Tuesday through Saturday.../from prev discussion/

A surface high will gradually build over the central Atlantic and
a broad surface low is expected to develop south of Jamaica early
in the fcst period. This will promote a moist south to southeasterly
wind flow across the local area throughout the workweek. However,
the best moisture content is expected to remain over the Hispaniola
and the Mona Passage. Regardless, the precipitable water content
is expected to range between 1.75 to around 2 inches from late Tuesday
through the end of the long term period. This moisture content in
combination with daytime heating and the sea breeze convergence
will cause afternoon shower and thunderstorm development over
portions of the interior and western PR. At upper levels, a polar
trough is expected to remain far north, and the sub-tropical jet
should remain northwest of the area as a ridge builds over the
eastern Caribbean for most of the period. In response the 500 mb
temperatures will increase by a degree or two, fluctuating between
-5 and -6 degrees Celsius, enough to support afternoon convection.

High temperatures are expected to range between the upper 80s and
low 90s in general across the urban areas and lower elevations of
the islands.


&&

.AVIATION...
(18Z TAFs)

Prevailing VFR conds at all TAF sites durg prd. SHRA/Isold TSRA will
cont ovr regional waters and local passages and en route btw
islands. Over land areas and until 23/22z SHRA/ Isold TSRA will dvlp
ovr the interior sections of PR and move northwards towards the
coastal areas. Isold SHRA psbl ovr coastal waters of the USVI
terminals with incr SHRA psbl aft 23/23Z, as a surface trough will
approach the region from the east. SFC wnds btw 8-12 knots with hir
gusts and sea breeze variations. L/LVl wnds veering fm SE-SW 10-15
kts BLO FL180 bcmg fm w and incr w/ht ABV.

&&

.MARINE...
Showers and thunderstorms will continue to affect portions of the
offshore Atlantic, Caribbean waters and Mona Channel through the rest
of the weekend. Tonight, the winds should remain light to gentle from
the east to southeast. On Sunday, the winds should become gentle to
moderate combine with a long- period north to northwest swell.
Therefore, small craft advisories were issued and will be in effect
from late Sunday into Monday particularly over the offshore and
nearshore Atlantic waters as well as along across the waters near
Virgin Gorda and Anegada Island. Hazardous marine conditions are
expected to prevail through early next workweek.

&&

.BEACH FORECAST...
Pulses from a northerly swell will begin to arrive the islands
tonight and into the workweek, with a high rip current risk for
the north-facing beaches of Puerto Rico, Culebra, Saint Thomas and
Saint John. The risk will increase to high in Saint Croix Sunday
night or Monday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Sunday night for PRZ001-002-
     005-008-010-012.

VI...High Rip Current Risk from Sunday evening through late Sunday
     night for VIZ001.

AM...Small Craft Advisory from midnight Sunday night to 5 PM AST
     Tuesday for AMZ711-712-716.

&&

$$

RADAR...ERG
MARINE....MMC