Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 032101
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
501 PM AST Sun Mar 3 2024

.SYNOPSIS...

Variable weather conditions will persist for the rest of the
night as moisture remains in the region. For Monday into Friday,
variable weather conditions will persist as well. Unstable weather
conditions are forecast for the last part of the workweek as an
upper-level trough moves to the area, resulting in more frequent
showers. Hazardous marine and coastal conditions will persist for
several days as a northeasterly swell invades the local waters.

&&

.SHORT TERM...Rest of Today through Tuesday...

Clusters of showers were observed during the early afternoon
hours across northeastern sections of Puerto Rico as a patch of
moisture filtered into the local region. This moisture will
persist for the remainder of the afternoon, increasing the
potential for shower activity across the interior and southwestern
sections of Puerto Rico. So far, at 5 PM, rainfall accumulations
were around one inch over Yauco and Sabana Grande, with other
areas reporting less than one inch. Daytime temperatures have
remained near normal, ranging from the low to mid-80s along the
coastal regions and around the 70s across the mountain areas.

For Monday, the islands will be influenced mainly by a surface
high pressure system in the northeastern Atlantic, extending into
the Caribbean. This surface feature will continue to promote east-
northeasterly winds across the region, bringing patches of shallow
moisture for the early morning hours of Monday. Consequently, the
islands can anticipate showers occasionally, affecting the
coastal areas, particularly in the northeastern sections in the
morning hours, followed by afternoon showers over the southwestern
and the western interior.

By late Monday into Tuesday, conditions will change at the mid-
level as the mid-level ridge weakens, leading to some instability.
At the same time, model guidances suggest another patch of
shallow moisture reaching the islands under the easterly winds.
This combination of factors will enhance the frequency of passing
showers across windward sections of the islands on Tuesday
morning, as suggested by the high-resolution models.

&&

.LONG TERM...Wednesday through Sunday...from previous
discussion...

Patches of moisture associated with a lingering surface trough
over the central Atlantic are expected to move close or north of
the region early in the forecast cycle under northeasterly
steering winds. This will promote shower activity across the
windward areas of the islands. Later in the workweek into the
weekend, an upper-level trough and associated surface front are
expected to exit the U.S. East Coast and move over the western
Atlantic. A broad surface high pressure over the north-central
Atlantic will shift southwards by the end of the week, causing the
winds to shift from the southeast. A warming trend is expected by
midweek. Meanwhile, the frontal system will absorb the weak
surface trough well north of the region.

By Thursday, the 500 MB temperatures could drop around -10 degrees
Celsius as the mid-to upper-level trough passes close to the area.
In addition, the moisture content will increase to around or just
above normal levels(1.45-1.60 inches) through Saturday as the
trade wind cap relaxes under the lighter southeasterly winds.
However, the 500 mb temperatures will warm to around -4C by
Saturday as a mid-level ridge builds over the central Caribbean.
In general, shower activity will increase from Thursday through
Saturday across Puerto Rico and the U.S. Virgin Islands. For
Sunday, northeasterly winds will return as a weak surface high
pressure moves north of the area, and overall fair weather
conditions should prevail as the mid-level ridge promotes drier
air and stable conditions aloft

&&

.AVIATION...
(18Z TAFS)
Mainly VFR conditions are expected through the period across TAF
sites. Passing showers may occasionally bring RA to SHRA with SCT-
BKN at FL015-030, and thus, brief MVFR conditions. However,
significant operational wx impacts are not anticipated at this time.
NE SFC winds btw 10-15 kts with gusts at 20-25 kts, diminishing to 5-
12 knots between 03/22Z and 04/12Z.

&&

.MARINE...

A surface high pressure system is generating northwestern winds
of moderate to locally fresh intensity across the region. As a
result, hazardous sea conditions persist across all exposed waters
and local passages for the next several days. For the upcoming
week , the combination of wind-driven waves and pulses of
northeasterly swell will sustain hazardous sea conditions of up to
8 feet across exposed Atlantic waters and passages. Therefore,
several small craft advisories are currently in effect; for more
information, consult the latest Marine Weather Message (MWWSJU).
Marine conditions should improve by Thursday.

.BEACH FORECAST...
A high risk of rip currents is in effect for the north and eastern
beaches of Puerto Rico, Culebra, and St. Croix. Dangerous coastal
conditions will persist until mid-week as the northeasterly swell
affects the north coastal areas. For additional information,
please refer to the latest Coastal Hazards Message (CFWSJU) and
Surf Zone Forecast (SRFSJU).

&&

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

VI...High Rip Current Risk through late Tuesday night for VIZ002.

AM...Small Craft Advisory until 2 AM AST Wednesday for AMZ711-712.

     Small Craft Advisory until 2 AM AST Tuesday for AMZ716-723-741-
     742.

&&

$$

SHORT TERM...WS
LONG TERM....LIS
AVIATION...MMC


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