093
FXCA62 TJSJ 060831
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
431 AM AST Sun Apr 6 2025

.SYNOPSIS...

Scattered showers and isolated thunderstorms in the afternoon
expected early this week. Variable weather pattern across the
region for the second part of the workweek, becoming wet over the
weekend. Marine and coastal conditions will continue improving
today, however, small craft and beachgoers should exercise
caution. A northeasterly long-period swell will arrive on Tuesday,
deteriorating marine and coastal conditions.

&&

.SHORT TERM...Today through Tuesday...

Partly cloudy skies prevailed across portions of the islands
overnight, with passing trade wind showers moving across the north-
central to eastern sections of Puerto Rico and across the U.S.
Virgin Islands. The Doppler radar estimated up to a quarter of an
inch of rain across northeastern PR. Minimum temperatures were from
the low to mid-70s across the lower elevations to the mid-60s across
the higher elevations. The wind was from the east to northeast up to
12 mph with gusts between 16 and 23 mph across coastal areas.

Surface high pressure over the western Atlantic will move and
strengthen over the central Atlantic over the next few days.
Moderate to fresh east-to-northeast winds will prevail today, but
winds will turn east to the southeast on Monday and Tuesday as the
high shifts eastwards. At the upper levels, a broad trough over the
northeastern Caribbean will continue to amplify, promoting
instability aloft and increasing the potential for isolated
thunderstorm development due to colder-than-normal 500 mb
temperatures of -9/10C. Therefore, isolated thunderstorms may occur
over western Puerto Rico. However, a limiting factor could be the
presence of drier air at the mid-levels. In response, the
precipitable water (PWAT) content is forecast to drop below 1 inch
during the next 24 hours before the remnants of an old frontal
boundary move over the local area by Monday evening, and the PWAT
recovers to nearly 1.50 inches. Across the USVI, fair weather
conditions will prevail throughout the period; however, scattered
showers will increase from Monday night into early Tuesday morning
with the surge in low-level moisture.

&&

.LONG TERM...Wednesday through Sunday...

The long-term forecast remains on track, with mainly stable
conditions over the second part of the work week and a wetter
pattern for the weekend. The broad high surface pressure over the
Western Atlantic will promote winds with an easterly component for
the long-term period. A mid to high level ridge will move over the
region by CWA by late Wednesday, warming 500 mb temperatures to
above normal ( -3 and -4 Celsius) and increasing stability aloft.
For the past few days, the model guidance has suggested a frontal
boundary approaching the local islands but solutions are delaying
its arrival and maintaining it north of the region. However, the
latest model solution shows an increase to above-normal
Precipitable Water values by Friday into the weekend, with the
arrival of high moisture content. As the high surface pressure
migrates eastward and 0 - 3 km winds turning from the ESE-SE,
showers should move along eastern PR, Vieques, Culebra, and the
U.S. Virgin Islands during the night into early morning. Although
deep convection activity will be limited, the combination of local
effects, sea breeze convergence, and diurnal heating could
enhance afternoon convection across interior and northwestern PR
each day. Rainfall accumulations could enhance flooding potential,
with ponding of water in roadways, urban, and poorly drained
areas, along isolated urban and small streams flooding.

The tendency of increasing temperatures in model guidance remains,
with highs reaching above normal values. Nevertheless, the risk
of heat remains low.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, trade wind -SHRA may cause brief
periods of -RA/VCSH across the area terminals. ENE winds will
increase between 13-17 kt with stronger gusts after 06/14z.

&&

.MARINE...

A broad surface high pressure over the western Atlantic will continue
promoting moderate to locally fresh easterly winds today and
continue to subside. However, small craft should exercise caution due
winds up to 20 knots and seas up to 6 feet. A northeasterly long
period swell will arrive early on Tuesday, increasing seas and
deteriorating marine conditions.

&&

.BEACH FORECAST...

As winds continue to subside, breaking waves between 3 - 5 feet
will promote a moderate risk of rip currents for most beaches of
Puerto Rico and the U.S. Virgin Islands. Life-threatening rip
currents are still possible along the surf zone, beachgoers
should exercise caution. A northeasterly long- period swell will
arrive early on Tuesday, deteriorating marine and coastal
conditions, and possibly increasing the risk of rip currents.

&&

.FIRE WEATHER...

Similar conditions to yesterday should prevail today. Winds will
remain between 15 - 20 mph, with higher gusts around 26 - 28 mph.
The latest KDBI values remain well above fire weather thresholds
in Guanica (637), while Cabo Rojo and Maricao slightly increased
(370 - 379). Soils in the southern coastal plains of Puerto Rico
continue with precipitation deficit and dry soils, contributing to
rapid fire spread. As a dry air mass filters into the region
today and relative humidities drop near 40 %, elevated fire
danger conditions are expected along the southern coastal plains
of Puerto Rico. Therefore, a Fire Danger Statement (RFDSJU) will
be issued for portions of southern Puerto Rico.

&&

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

$$

SHORT TERM/AVIATION...DS
LONG TERM/MARINE...MNG