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537
FXCA62 TJSJ 280725
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
325 AM AST Tue Apr 28 2026

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

.KEY MESSAGES...
Updated at 317 AM AST Tue Apr 28 2026

* Showers and isolated thunderstorms are expected across the
  islands today, increasing the flooding and lightning risk,
  resulting in urban and small stream flooding, particularly
  across northern Puerto Rico in the afternoon.

* A moderate rip current risk continues over north and east-
  facing beaches Puerto Rico and the U.S. Virgin Islands for the
  next several days. Beachgoers should exercise caution along
  exposed beaches.

* Warmer-than-normal conditions will continue across urban and
  coastal areas of the islands, with heat indices reaching or
  exceeding 100F, affecting the more vulnerable communities.

&&

.Short Term(Today through Thursday)...
Issued at 317 AM AST Tue Apr 28 2026

Overall, relatively calm weather conditions prevailed across Puerto
Rico and the U.S. Virgin Islands under partly to mostly cloudy
skies. Radar and satellite imagery captured a line of showers
developing just off the southern coast of Puerto Rico during the
early morning hours. While some of this activity reached the
coastline between Guanica and Ponce, rainfall accumulations
remained minimal. Meanwhile, additional lines of showers moved
across the Caribbean Sea, remaining mostly south of St. Croix
throughout the night, though a few brushed the island with little
to no accumulation. Overnight low temperatures ranged from the mid
to upper 70s across coastal and urban areas, while the central
mountain range saw cooler temperatures in the upper 60s to low
70s. Winds remained light and variable at 5 knots or less.

For the remainder of the morning, shower frequency is expected to
increase across portions of southern and eastern Puerto Rico, as
well as the U.S. Virgin Islands. This is due to abundant moisture
filtering into the region, which will facilitate further
development. Current precipitable water values indicate above-normal
moisture levels of approximately 2 inches, a trend expected to
persist through at least the end of the workweek. At the surface, a
high-pressure system will maintain a light southerly steering flow
through Wednesday. The flow is anticipated to shift from the east-
northeast on Wednesday morning before returning to the east-
southeast by the afternoon as the surface high migrates from the
central to the eastern Atlantic.

Throughout the rest of the period, afternoon convective activity is
likely to produce moderate to heavy rainfall and thunderstorms
across the interior and toward northern and northwestern Puerto
Rico. This activity will be driven by the combination of deep
moisture, daytime heating, and local effects. Because winds are
light, these showers will move slowly and expand in coverage,
persisting over the region for longer time. Therefore, the risk of
flooding will be elevated today, particularly during the afternoon
hours. Periods of heavy rainfall, lightning, and ponding on roadways
are likely, with localized flooding possible in areas where rain
persists.

Despite the anticipated rainfall, warm to hot temperatures will
continue across the islands. A limited heat risk is expected through
next week due to the combination of above-normal temperatures,
southeasterly flow, and increasing humidity.

&&

.Long Term(Friday through Tuesday)...
Issued at 317 AM AST Tue Apr 28 2026

By the end of the week, a moist and unstable weather pattern will
persist across Puerto Rico and the U.S. Virgin Islands, accompanied
by a troughing pattern aloft, light to moderate southeasterly winds,
and above-normal moisture across the forecast area. Current guidance
suggests that precipitable water values will remain in the 75th
percentile for this time of year, around 1.80 to 2.00 inches. This
will continue to support a pattern of showers across windward areas
early in the day, followed by active afternoon convection across the
interior, northern, and northwestern portions of Puerto Rico. In
addition, 500 mb temperatures will remain between -7 and -8 degrees
C (near normal but sufficient to support isolated thunderstorm
development), particularly where the strongest activity develops
during the afternoon on Friday. Accordingly, a limited flood threat
will persist on Friday due to the high potential for ponding of
water on roads and in poorly drained areas.

From Saturday into early next week, a gradual drying trend is
anticipated, leading to improving weather conditions. Precipitable
water values will decrease to near-normal levels (around 1.5 inches
or less), while 250 mb heights increase and 500 mb temperatures warm
as ridging builds aloft, bringing greater atmospheric stability.
Although afternoon showers may still develop due to local effects,
their coverage and intensity will be reduced. Any shower activity
during this period should be brief and limited.

Lastly, warm conditions will persist throughout the period as
indicated by temperature guidance at 925 mb which suggests values
will remain above normal through at least next weekend. Also, an
east to southeasterly wind flow will prevail supporting those
conditions. Maximum surface temperatures will range from the upper
80s to low 90s across coastal and urban areas, and from the low to
mid 80s in higher elevations. Combined with high humidity, heat
indices are expected to exceed upper 90s to low 100s degrees F each
day. As a result, a limited heat threat will remain in place for
urban, coastal, and low-elevation areas. Residents and visitors are
encouraged to stay hydrated and avoid prolonged sun exposure during
peak heat hours.

&&

.AVIATION...
(06Z TAFS)
Issued at 317 AM AST Tue Apr 28 2026

Mainly VFR conds expected at all TAF sites. Light/variable to
calm winds early in the morning, becoming SSE btw 8-12 kt after
28/14Z. SHRA/TSRA may develop over interior/western PR and affect
TJSJ/TJBQ btw 27/17-23Z, causing brief MVFR/IFR conds. VCSH are
possible over eastern PR/USVI terminals after 27/23Z.


&&

.MARINE...
Issued at 317 AM AST Tue Apr 28 2026

A surface high pressure system over the central Atlantic will
continue to weaken, while a surface low strengthens over the
northwestern Atlantic over the next few days. This weakening
pressure gradient will promote light to gentle southeasterly winds
through at least midweek, becoming more easterly by the latter part
of the week. A surface trough over east of Puerto Rico combined with
an upper-level trough will bring showers and isolated thunderstorms
across the local waters today. Pulses of small, long- period
northeasterly swell will continue to spread across the Atlantic
waters and local passages for the next few days, though seas
should remain between 2 and 4 feet.

&&

.BEACH FORECAST...
Issued at 317 AM AST Tue Apr 28 2026

Pulses of a small, long- period northeasterly swell will continue to
spread across local waters and passages, with conditions expected to
diminish by Thursday. Moderate risk of rip currents will prevail
along the northern and eastern beaches of Puerto Rico and the U.S.
Virgin Islands. Although the risk remains low to moderate,
beachgoers must exercise caution as life-threatening rip currents
are possible along beaches under moderate risk. In addition to rip
currents, beachgoers should remain weather alert as afternoon
showers and thunderstorms are expected near northern coastal areas
of Puerto Rico, resulting in heavy rainfall, gusty winds, and
lightning.

&&

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

$$

SHORT TERM...GRS
LONG TERM....YZR
MARINE/BEACH...MMC

NWS SJU Office Area Forecast Discussion