630
FXCA62 TJSJ 201842
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
242 PM AST Fri Mar 20 2026

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

.KEY MESSAGES...
Issued at 242 PM AST Fri Mar 20 2026

* For the rest of the afternoon, showers may develop across interior
  and western Puerto Rico, but no significant impacts are expected.

* Across the U.S. Virgin Islands, expect generally fair weather with
  passing trade wind showers at times.

* A moderate risk of rip currents will continue along north and east-
  facing beaches through the weekend.

* A frontal boundary approaching from the northwest will bring
  increasing showers and a more unsettled weather pattern from
  Saturday into early next week.

* Periods of heavy rain and thunderstorms may lead to localized
  flooding, lightning hazards, and hazardous marine and beach
  conditions.

&&

.Short Term(This evening through Sunday)...
Issued at 242 PM AST Fri Mar 20 2026

Mostly tranquil conditions have prevailed through much of the
day, with the exception of a few passing showers across eastern
and southeastern Puerto Rico. The 12Z morning sounding indicated a
precipitable water (PWAT) value of 1.15 inches, which is below
average. Daytime high temperatures have been warm, ranging from
the mid to upper 80s across coastal areas to the low 90s, while
the mountainous regions have remained in the upper 70s. For the
remainder of the afternoon, showers may develop across the
interior and western portions of Puerto Rico, however, no flooding
impacts are expected.

Over the weekend, a transition to a wetter and more unsettled
pattern is expected. Despite the increase in tropical moisture
associated with southerly flow, model guidance continues to
suggest limited overall rainfall accumulations on Saturday. The
wettest conditions, or strongest model signal, are currently
expected on Sunday as the front settles over the region. Latest
model guidance and satellite-derived PWAT data indicate moisture
trailing from frontal boundary to the northwest, forecast to move
into the northeastern Caribbean late tonight into Saturday
morning. PWAT values will then increase through Sunday, rising
from around 1.00 inch today to nearly 1.80 inches through Sunday
(around the 75th percentile, above normal for this time of year).
Another factor to note, is that winds will remain around 10 knots
or less as the local pressure gradient weakens, particularly on
Sunday. This combination of increased moisture and weak steering
flow will favor slow-moving showers and as a consequence an
elevated flooding risk, especially in urban areas, roads, small
streams, and poor drainage areas as the potential for greater
accumulations increases. The U.S. Virgin Islands will remain on
the drier side of the frontal boundary through early Saturday,
with shower coverage gradually increasing by Sunday.

Overall, rainfall activity is expected to remain variable on
Saturday, with only isolated to scattered showers and less
impacts. By Sunday, more widespread and persistent rainfall is
anticipated, increasing the potential for localized flooding
across Puerto Rico.

&&

.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...
(18Z TAFS)
Issued at 242 PM AST Fri Mar 20 2026

Mainly VFR conds expected to prevail across all TAF sites. VCSH
and brief -RA possible, mainly ovr W PR and and within streamers
downwind of the TIST, leading to brief MVFR conds possible. TJPS
and TJSJ have the better chance to observe VCSH/-RA overnight and
Sat morning. Sfc SE to S winds at 10-12 kts or less with sea
breeze variations and occasional higher gusts. Winds bcm
lighter/vrb overnight, then incr to 10-12 kts again aft 21/13Z.

&&

.MARINE...
Issued at 242 PM AST Fri Mar 20 2026

Light to moderate southeast winds will prevail across the regional
waters in the short term. Choppy seas may 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 approach the region from the
northwest, winds will weaken and shift from the southeast to
southerly through the weekend, becoming light and variable at times.
However, this boundary could promote localized hazardous marine
conditions, particularly across the Atlantic waters and the Mona
Passage. As high pressure builds over the western Atlantic early
next week, winds will turn northeasterly and increase, resulting in
deteriorating marine conditions once again. Unsettled weather will
develop from the weekend into early next week, leading to increased
shower activity across the local waters.

&&

.BEACH FORECAST...
Issued at 242 PM AST Fri Mar 20 2026

Beach conditions have begun to improve, as winds and seas have
gradually decreased 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 persists
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 exercise
caution. A low risk is expected along more protected southern
beaches.

In addition, the development of heavy showers and isolated
thunderstorm activity associated with an approaching frontal
boundary may result in localized hazardous beach conditions,
including reduced visibility, gusty winds, dangerous surf, and
lightning. Thunderstorms will pose a significant lightning risk,
particularly for those in or near the water, and beachgoers should
be prepared to seek shelter quickly if storms develop.

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/AVIATION...YZR
LONG TERM...ICP
MARINE/BEACH...CVB

NWS SJU Office Area Forecast Discussion