672
FXCA62 TJSJ 222054
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
454 PM AST Wed Jan 22 2025

.SYNOPSIS...

A trade wind perturbation will gradually increase the frequency of
showers late tonight into early Thursday morning. Ponding of
water in roads and poorly drained areas are likely across windward
coastal areas of the islands. Choppy wind- driven to hazardous
seas will persist for most of the workweek, maintaining dangerous
conditions for small craft and promoting life- threatening rip
currents.

.SHORT TERM FORECAST...Tonight through Friday...

This morning, showers affected the eastern half of Puerto Rico,
Vieques, Culebra, Saint Thomas, and Saint John, with rainfall
amounts ranging from 0.01 to 0.30 inches. Winds remained around 5 to
15 mph, with occasional higher gusts near coastal areas. Some
weather stations even reported wind gusts in the upper 20s and lower
30s. Temperature-wise, they stayed in the 80s to low 90s along the
coastal/urban areas, while in mountainous/rural areas, they were in
the 70s.

As we move into the overnight hours, rainfall activity is expected
to increase gradually. A perturbation in the trade winds will move
through the forecast area, with model guidance indicating
precipitable water values between 1.4 and 1.7 inches (above normal
values for this time of the year). The highest moisture content will
remain concentrated below or near the 700mb level through early
Thursday. At this time, we foresee ponding of water in roads and
poorly drained areas.

By the end of the workweek, we anticipate a slight improvement in
weather conditions as some dry air begins to filter into the region.
However, expect mostly variable weather through the remainder of the
short-term forecast period as a high-pressure system dominates the
region, and the easterly winds continue to bring somewhat breezy
conditions. Therefore, residents can expect mostly partly cloudy
skies with occasional light to moderate showers across eastern
sections of Puerto Rico.

.LONG TERM...Saturday through Wednesday...

.PREV DISCUSSION... /issued 459 AM AST Wed Jan 22 2025/

A deep-layered ridge is expected to persist over the Tropical
Atlantic throughout the long-term period. A short-wave trough is
expected to cause a brief weakness aloft over the region on
Sunday, and a pre-frontal trough is expected to develop mainly
north of the region during the weekend. Another upper level trough
is expected to move over the area on Tuesday, and the 500 mb
temperatures are forecast to drop near -7C. However, the
precipitable water content is forecast to remain at normal to
below normal levels through the entire forecast period, and
showers across the area will be driven mostly by the remnants of
old frontal boundaries that the trade winds will carry from time
to time.

Normal to above-normal temperatures are expected to prevail
throughout most of the long-term period, particularly in the
coastal and lower elevations of the islands. Daytime highs will
range from the mid to upper 80s and low 90s in coastal and urban
areas, while the mountains will experience highs in the mid to
upper 70s. Minimum temperatures will range from the low 60s in the
higher elevations to the mid and upper 70s in the lower elevations
of the islands.

.AVIATION...
(18z TAFs)

VFR conditions will persist across the TAF sites during
the period. Winds will continue to be variable at the eastern sites,
on TIST & TJSJ as the wind perturbation moves north of the region.
Winds will diminish at around 2223Z, increasing again at 2315Z for
all the sites. VCSH to SHRA are forecast between 2223-2310Z,
lowering ceilings and reducing the VIS in some isolated areas.

.MARINE...

A surface high pressure across the central Atlantic will support
moderate to locally fresh easterlies for the next several days.
Choppy wind-driven to hazardous seas for small craft will continue
across portions of most local waters and passages. Small craft
advisory conditions are likely to continue through the end of the
week for some offshore areas.

.BEACH FORECAST...

Windy conditions across the region will continue to promote life
threatening rip currents, especially along the northern and
eastern exposed beaches of the islands. Elsewhere, the risk of
rip currents will be moderate. These conditions are expected to
persist at least through the end of the workweek.

&&

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

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

AM...Small Craft Advisory until noon AST Saturday for AMZ711-723.

     Small Craft Advisory until 6 PM AST this evening for AMZ712-716-
     726-733-741.

&&

$$

SHORT TERM/AVIATION...LIS
LONG TERM...DS
MARINE...MRR
BEACH FORECAST...CVB