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348
FXCA62 TJSJ 200650
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
250 AM AST Fri Mar 20 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 211 AM AST Fri Mar 20 2026

* Diurnally induced afternoon showers are expected to develop over
  portions of the Cordillera and along the northern slopes of
  Puerto Rico.

* Across the U.S. Virgin Islands, mostly sunny to partly cloudy
  skies are expected with occasional trade wind showers.

* Life-threatening rip currents will remain possible (moderate
  risk) along the east and north facing beaches of Puerto Rico,
  Culebra, and the U.S. Virgin Islands through the weekend.

* A frontal boundary and associated trough will increase shower
  activity from early Saturday through Sunday, bringing periods
  of unsettled weather across Puerto Rico and the U.S. Virgin
  Islands.

&&

.Short Term(Today through Sunday)...
Issued at 211 AM AST Fri Mar 20 2026

Mostly clear to partly cloudy skies were observed across the
islands during the early morning hours. Light passing showers were
noted mainly over the waters and across portions of eastern and
southern Puerto Rico. Minimum temperatures were from the low 60s
across the higher elevations to the mid 70s across coastal areas.
Winds were from the southeast at 10 mph or less.

A transition to a significantly wetter and more unsettled pattern
is expected this weekend. Latest satellite and precipitable water
imagery shows a deep plume of moisture trailing a frontal boundary
to our northwest, which model guidance brings into the
northeastern Caribbean by late tonight into Saturday morning.
Moisture advection will gradually increase PWAT values from near
1.00 inch to roughly 1.751.80 inches (well above the 75th
percentile) by Saturday, and they will remain elevated through
Sunday. As this frontal boundary filters in, the local pressure
gradient will relax, causing steering winds to drop from around
18 knots down to around 10 knots or less. This combination of
higher moisture pooling and weak steering winds is expected to
lead to slow-moving showers, which, in turn, increases the risk of
urban, small stream, and localized flash flooding across PR.

For today, diurnally driven shower activity is expected, initially
focusing across the interior and southern sections of Puerto
Rico, and over the northern sections during the afternoons.
However, the flood threat is not expected to increase until
Saturday afternoon through Sunday, as the moisture axis from the
front settles over the region, resulting in a wetter period across
PR. Rainfall accumulations are currently forecast to range from
1.50 to 2.50 inches across the interior, eastern, and southern
portions of Puerto Rico, but locally higher amounts cannot be
ruled out. The U.S. Virgin Islands will remain on the drier side
of the front through early Saturday before shower coverage
gradually increases by Sunday.

&&

.Long Term(Monday through Friday)...
Issued at 211 AM AST Fri Mar 20 2026

A broad mid to upper level trough pattern will persist across the
western Atlantic and northeastern Caribbean through much of the
workweek. A jet streak near the region at the start of the period
will provide enhanced divergence aloft and support generally
unstable conditions, weakening slightly and lifting northward later
in the week but remaining close enough to influence the local area.
At the surface, high pressure building over the western Atlantic
will promote a transition to northeasterly winds early in the week,
persisting through midweek and supporting a cooler and more stable
low-level flow. Moisture will remain near to above normal, initially
extending to around the mid levels and becoming deeper by midweek
onward, despite occasional intrusions of drier air aloft. Weak mid-
level perturbations early in the period will gradually lift
northward, while a surface-induced trough or trade wind perturbation
associated with a mid-level disturbance may approach the region
later in the week, enhancing low-level convergence.

Unsettled weather conditions will persist through the workweek, with
hazards initially focused on excessive rainfall and thunderstorms.
Early in the period, lighter steering flow and sufficient moisture
will favor slow-moving showers, increasing the risk of urban and
small stream flooding, along with frequent lightning. As
northeasterly winds become established, showers will favor windward
areas, with afternoon convection over interior and western Puerto
Rico. From midweek onward, deeper moisture and continued upper-level
support will lead to more efficient rainfall processes, maintaining
an elevated flooding risk. In addition, the wind threat may increase
later in the week as stronger low-level flow and passing
perturbations support periods of gusty winds, particularly in and
near heavier showers and thunderstorms.

&&

.AVIATION...
(06Z TAFS)
Issued at 211 AM AST Fri Mar 20 2026

Mainly VFR conditions are expected to prevail across all terminals
through the forecast period. Mostly VCSH expected, but -RA and
tempo MVFR cigs are possible at TJBQ/TJPS/TJSJ this afternoon due
to locally induced SHRA. Low-level winds will continue from the SE
at 10-15 kt.

&&

.MARINE...
Issued at 211 AM AST Fri Mar 20 2026

Choppy seas will persist across portions of the Atlantic waters due
to moderate to locally fresh winds, and small craft should continue
to exercise caution. As a pre-frontal trough and associated frontal
boundary approaches the region, winds will continue to weaken and
shift from the southeast to southerly through the weekend, becoming
light and variable. As a high pressure builds over the western
Atlantic early next week, winds will turn northeasterly and increase,
resulting in deteriorated marine conditions once again. Unsettled
weather will also develop during the weekend into early next week,
leading to increasing shower activity across the local waters.

&&

.BEACH FORECAST...
Issued at 211 AM AST Fri Mar 20 2026

Beach conditions have begun to improve, as winds and seas have
gradually decrease across the coastal waters. Nevertheless, we
urge visitors and residents to remain alert and monitor the
forecast for updates or changes as a MODERATE risk of rip currents
persist along the northern and eastern beaches of Puerto Rico,
Vieques, Culebra, and the US Virgin Islands, through the weekend.
A moderate risk means that life-threatening rip currents are still
possible in the surf zone, and beachgoers should remain alert and
cautious. A low risk is expected along more protected southern
beaches. For additional information and location- specific rip
current details, please visit: weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...DSR
LONG TERM....ICP
AVIATION...DSR
BEACH/MARINE...MNG

NWS SJU Office Area Forecast Discussion