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000
FXCA62 TJSJ 182033
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
433 PM AST Thu Apr 18 2024

.SYNOPSIS...

Moderate to heavy showers will continue across the the southern
and eastern portions of Puerto Rico through the early evening
hours. This may result in additional flooding and mudslides in
steep terrain along the Cordillera Central. Weather conditions
will slowly improve tonight into Friday as a mass of drier air
filter into the region. A surface high-pressure migrating from the
western Atlantic to the Central Atlantic will promote mostly fair
conditions with showers in the afternoon hours.

&&

.SHORT TERM...Tonight through Saturday...

Mainly fair weather conditions prevailed during the morning hours
across the local islands under partly cloudy skies. As the day
progressed, cloudiness began to increase along the Cordillera
Central and the southern slopes of Puerto Rico. Locally heavy
showers were observed from Yauco to Orocovis, and from Barranquitas
to Humacao. Doppler radar estimated rainfall accumulations between 2
to 4 inches of rain across the mentioned areas. Flood Advisories
(FLS) were issued, due to minor flooding, ponding of water in low
drainage areas and the potential for mudslides. Daytime temperatures
were observed in the low to mid 80s across Puerto Rico and the U.S.
Virgin Islands. Winds were light to moderate from the northeast with
higher gusts.

The shower activity is expected to prevail until the early evening
hours, and the majority of the activity will diminish around sunset.
Despite of the shower activity staying mostly across central and
southern Puerto Rico, the northern and northeastern municipalities
may observe late convection later this afternoon. By tonight into
Friday weather conditions will improve. However, passing showers
cannot be ruled out across the windward portions of the islands.
 As the upper level trough moves away from the area, a building high
pressure in the western Atlantic will promote winds from the NNE. A
mass of drier air will slowly filter into the area, limiting the
shower formation from Friday into Saturday. Nonetheless, due to
daytime heating and local effects, shower activity is possible
across the central and southwestern areas of Puerto Rico during the
afternoon hours. The U.S. Virgin Islands will observe mainly fair
weather conditions through the weekend. Overall, nighttime t
temperatures will stay in the upper 60s across the higher
elevations, and in the mid 70s across the coastal and urban areas
of the islands.

.LONG TERM...Sunday through Thursday...

.PREV DISCUSSION.../Issued 510 AM AST Apr 18 2024/

A surface high-pressure building north of the islands, promoting
an advective pattern, will bring occasional moisture surges across
the USVI and PR from Sunday onward. The winds will persist mainly
from the east to east-northeast, which may result in the areas
affected by passing showers being the islands` north and east
windward sections, especially during the night and morning hours.
These showers will bring periods of moderate to locally heavy
rains at times. The afternoon convection will be driven mainly by
local effects, diurnal heating, and sea breeze variations across
the interior and western sections daily. Additionally, the latest
model guidance suggests maximum temperatures near the normal
climatological values during the long term.

Around mid-week, an upper-level trough will approach from the
west, increasing the local instability, which, combined with the
sea breeze, orographic effects and diurnal heating could result in
the typical strong afternoon convection of a wet April.

&&

.AVIATION...
(18z)

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, tempo MVFR conds are
possible at TJPS thru 18/23z. Low level winds will continue from
the north- northeast around 10 kt.

&&

.MARINE...

A set of surface troughs, one to the northwest and other to the
northeast of the islands will promote light to locally moderate
northeast winds today into Friday. A small northeasterly swell will
move across the Atlantic waters through the weekend. The surface
trough northeast of the region and a surface high pressure building
across the western Atlantic will promote moderate to locally fresh
trades by the weekend.

&&

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

$$

SHORT TERM...LIS
LONG TERM....GRS
PUBLIC DESK/UPPER AIR...MRR