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000
FXCA62 TJSJ 162019
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
419 PM AST Tue Apr 16 2024

.SYNOPSIS...

Unstable weather conditions are expected to prevail across the
local area through at least Wednesday. Showers and isolated
thunderstorms are also expected during the overnight hours.
Therefore, there is the potential for minor flooding, river rises
and mudslides due to soil saturation. This wet pattern will
continue for the next few days. Marine conditions will slowly
improving across the local waters, however, another northeasterly
swell is forecast to arrive Thursday.

&&

.SHORT TERM...Tonight through Thursday...

Moderate to heavy showers and thunderstorms were observed across the
eastern half of the region during the morning hours. These showers
and thunderstorms continued to produced areas of locally heavy rains
and frequent lightning mainly over the coastal waters. This activity
persisted over portions of the northern U.S. Virgin Islands and the
eastern half of Puerto Rico through at least noon. Doppler radar
estimated rainfall accumulations between 1 to 2 inches in St. Thomas
and St. John, and between 2 to 4 inches across the eastern half of
Puerto Rico. Isolated sectors of the metropolitan area of Carolina
received up to 5 inches. The Luis Munoz Marin Int. Airport in San
Juan had a max temperature of 84 degrees Fahrenheit today. Overall,
daytime temperatures were seen in the upper 70s to low 80s across
all the islands. Winds were light to moderate with higher gusts with
the strongest showers.

During the afternoon hours daytime heating, local effects and
sufficient available moisture helped to the formation of showers
across the northwestern portions of Puerto Rico. These moderate to
locally heavy showers will persist through late this afternoon.
Active and unstable weather is expected to remain through at least
Wednesday, due to the presence of an upper level trough. The trough
with its axis located over the Hispaniola, will continue to move
east. Therefore, we should expect active weather for during the
overnight hours into the morning hours throughout much of the
region. The latest Precipitable Water content Analysis (PWAT) shows
values of 1.70 to 1.98 inches until at least Thursday. This pattern
will favor the enhancement of showers and isolated thunderstorms
across portions of the islands and the local waters for the next
several days.

At this time, soils are saturated and any additional rains may lead
to ponding of water and flooding in flood prone areas. In addition,
quick river rises and water surges with flash flooding, and
landslides are possible. Overnight temperatures will stay in the mid
to upper 60s across the higher elevations, and in the low to mid 70s
across the coastal and urban areas of the islands.

.LONG TERM...Friday through Tuesday...

.PREV DISCUSSION.../Issued 452 AM AST Apr 16 2024/

Areas of low pressure spread across the western to central Atlantic
basin will maintain moderate NE winds through the weekend along with
enough water content in a lingering airmass to allow passing showers
and afternoon convection to fire up during the afternoon due to
local effects. By Sunday, the location of a surface high in the
western Atlantic will assist the lifting of a moist airmass from the
eastern Caribbean. This in combination with a mid to upper-level
trough, with the jet max over the region by Saturday through late
Sunday, will allow an increase of passing showers and afternoon
convection mainly across western Puerto Rico. Winds begin to
strengthen and veer, becoming more easterly to southeasterly Monday
to Tuesday, respectively, as the aforementioned surface high moves
into the central Atlantic. Elevated Precipitable water values and
breezy conditions will allow a wet pattern to prevail.

&&

.AVIATION...
(18Z TAF)

Areas of SHRA and SCT TSRA over Hispaniola will move close to
terminals this evening for TJBQ and late tonight for TJSJ/TIST
reducing VIS and CIG. This will produce possible MVFR/IFR conds and
mtn obscurations. Sfc winds ESE 10-20 kts with gusts to 25 kts psbl
till 16/22Z. Overnight winds will be 6-12 kts with some hir gusts.

&&

.MARINE...

A surface ridge over the north-central Atlantic and broad surface
trough across the eastern Caribbean will generate moderate to locally
fresh east-southeasterly winds through Wednesday. A fading northerly
swell and choppy wind driven seas will continue to promote choppy
seas across the Atlantic waters. An upper level trough and induced
surface trough will continue to promote inclement weather across the
local waters over the next few days, with squally weather and
thunderstorms possible at times. Another long-period northeasterly
swell is forecast to arrive by Thursday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 AM AST Wednesday for AMZ711.

&&

$$

SHORT TERM...CVB
LONG TERM...GRS
PUBLIC DESK...MRR