652
FXCA62 TJSJ 310851
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Fri Jan 31 2025

.SYNOPSIS...

Isolated to scattered showers will likely continue this morning
resulting in variable weather conditions today, followed by a
drier airmass tonight. A weak Saharan Air Layer will continue
fill and linger through the weekend. Breezy conditions will
prevail through the weekend, with passing showers moving from time
to time during the night and early morning hours under an
advective weather pattern.

&&

.SHORT TERM...Today through Sunday...

A variable weather pattern persisted through the night, with
isolated to moderate showers affecting the eastern sections of
Puerto Rico and the U.S. Virgin Islands. After 2 AM, shower activity
shifted toward the northern portions of Puerto Rico, impacting areas
from the San Juan metro to Aguadilla. Notably, intense rainfall was
observed over Barceloneta and some sections of the San Juan Metro
area, where Doppler radar estimates indicated nearly half an inch of
accumulation. Overnight temperatures ranged from the low to mid-60s
across the mountainous regions and the low to mid-70s along the
coastal areas.

The variable weather pattern will continue through the morning and
early afternoon as a weak induced surface trough continues the path
across the region. This disturbance will bring increased cloudiness
and moisture, resulting in a wet morning across most of the islands
and a variable afternoon. However, rainfall accumulations are
expected to remain low, with only a limited ponding of water on
roadways. Winds will remain strong to vigorous from the east-
northeast due to the influence of a strengthening high-pressure
system over the western Atlantic and its interaction with a nearby
frontal boundary.

For Saturday into Sunday, model guidance suggests some instability
across the region as a strong upper-level trough, located just east
of the area, erodes in someway the mid-to-upper-level ridge. This
will result in colder temperatures at the 500 MB level. However,
despite this instability, limited surface moisture and the arrival
of a dry air mass with Saharan dust particles will contribute to
mostly stable weather conditions. Any showers that develop will be
driven by local and diurnal effects. As a result, hazy skies will be
present by Saturday with no-significant flooding threat expected.

&&

.LONG TERM...Sunday through Friday...

The long-term forecast will be characterized by variable weather
conditions. According to the latest model guidance, a mid-level
ridge is expected to build over Cuba and the Bahamas at the start
of the week, bringing stability to the middle and upper levels of
the atmosphere. Precipitable water values are likely to fluctuate
between below-normal and seasonal levels, ranging from 1.00 to
1.5 inches. A mix of moisture and dry air pockets will move within
the trades daily, resulting in typical conditions where showers
develop, mainly affecting coastal and windward areas during the
night and early morning hours. In the afternoons, localized
convection may form over western Puerto Rico, primarily due to
daytime heating and sea breeze interactions.

Winds will continue with an east-northeast component throughout
the week, driven by high pressure over the Atlantic. This will
keep conditions breezy, especially along coastal areas of the
islands. For this reason, any showers that develop are expected to
move quickly, and while there are no flooding concerns at the
moment, ponding of water on roads and in poorly drained areas is
likely. Residents and visitors are encouraged to exercise caution
on roadways.

By mid to late week, a stronger high pressure system will
establish itself over the western Atlantic, tightening the
pressure gradient even further across the region, which will keep
winds breezier. Daytime temperatures are expected to range from
the mid to upper 80s in lower elevations and mid to upper 70s in
higher elevations, with overnight lows in the 70s and 60s,
respectively.

&&

.AVIATION...
(06z TAFs)

VFR conditions will persist for all the TAF sites during the
period. VCSH and -RA will persist across most of the TAF sites at
least until 31/19Z. Winds will increase from the E-NE, increasing
to 15 knots with gusty winds. After 31/23Z winds will slightly
diminish becoming from the E at 10 knots.

&&

.MARINE...

A weak induced surface trough will continue to move across the
region this morning resulting in isolated to scattered showers
across the local waters. A building surface high pressure over the
western Atlantic will promote moderate to locally strong east to
northeast winds from today onward. These increasing winds, along
with a small northerly swell, will promote choppy to hazardous seas
across most of the local waters through at least early next week.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents along all the coastal
areas of Puerto Rico, including Vieques and Culebra, and along
the U.S. Virgin islands. This means that life-threatening rip
currents are possible in the surf zone and beachgoers should
exercise caution. A small northwesterly swell and choppy wind-
driven waves will increase the risk of rip currents later during
the weekend.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 PM AST Sunday for AMZ711.

     Small Craft Advisory from 6 AM Saturday to 6 PM AST Sunday for
     AMZ723.

     Small Craft Advisory from 6 PM this evening to 6 PM AST Sunday
     for AMZ733-741.

&&

$$

SHORT TERM/AVIATION...LIS
LONG TERM/MARINE/BEACH FORECAST...YZR