692
FXCA62 TJSJ 262149
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
549 PM AST Fri Apr 26 2024


.SYNOPSIS...

Unstable weather conditions are expected to prevail through at
least tomorrow with limited to elevated risks of flash flooding,
urban and river flooding, and landslides mainly over the western
interior and southwestern sectors of PR. A slight improvement on
weather condtions is expected by Sunday into early next week. We
encourage citizens to stay informed and monitor our forecast for
additional updates. A northerly swell is anticipated to spread
across the local waters early next week briefly deteriorating
coastal and marine conditions.

&&

.SHORT TERM...Tonight through Sunday...

Partly cloudy to cloudy skies prevailed across Puerto Rico and the
U.S. Virgin Islands today. During the morning hours, calm weather
conditions dominated with mostly easterly winds between 5 to 10
mph. Low temperatures across the coastal areas ranged around the
mid-70s and in mountains and valleys around the mid-60s. Daytime
highs peaked mainly in the 80s to lower 90s along the coasts and
70s to 80s across the mountains.

During the early hours of the afternoon, as had been anticipated,
showers and thunderstorms began to develop across the western
interior and western Puerto Rico. At the moment, the activity has
already been decreasing, but radar estimates recorded up to 2
inches of rain in municipalities such as Aasco, Jayuya, Las
Maras, Utuado, Adjuntas, and Lares, flood warnings were issued in
those regions.

The forecast for the overnight hours remains without much changes,
it is expected that showers will then increase across the U.S.
Virgin Islands by late this afternoon into the evening and early
tomorrow morning as a plume of moisture moves towards us,
resulting in showery weather, with possible isolated thunderstorms
moving inland from the surrounding waters. Rainfall models are
showing that this activity should continue in sectors of eastern
Puerto Rico and move towards the rest of the island for the rest
of the day (Saturday). Winds shift to the northeast tomorrow as
surface high pressure moves from the eastern seaboard into the
western Atlantic. Therefore, the latest model guidance suggests
that the highest accumulations should be in the SW quadrant of
Puerto Rico. For that reason, the risk of flooding remains
elevated tomorrow, we encourage residents and visitors to exercise
caution on the roads and monitor any additional advisories if
they are issued.

For Sunday, winds are expected to start becoming breezier. The
latest precipitable water models continue to show above normal
values for that period, but some models are showing a slight
improvement in terms of less rain accumulations, but in any case,
at this point some activity is expected for the morning hours to
the northern and eastern Puerto Rico, then towards the interior
and southwest quadrant.

&&

.LONG TERM...Monday through Friday...
.PREV DISCUSSION.../issued 417 AM AST Fri Apr 26 2024/

A strong surface high pressure located over the eastern coast of
the United States will promote a northeasterly wind flow from
Monday through Wednesday. As this feature moves from the western
to the central Atlantic winds are expected to veer from a more
easterly component through the rest of the long-term period.
Previous model runs indicated a drying trend for the beginning of
the workweek, however, the latest model guidance now suggests a
prolongation of above-normal moisture across the islands. The
precipitable water content values are between 1.60 to 1.80 until
Wednesday, then increasing up to 2.20 inches through the rest of
the period. A vast moisture field coming from South America to the
eastern Caribbean will help to enhance the shower and
thunderstorm activity across the islands. This wet and unstable
weather pattern will promote rainfall activity everyday across the
area, especially over portions along the Central Cordillera,
eastern, and western portions of Puerto Rico. The U.S. Virgin
Islands will also experience moderate to locally heavy showers by
the end of the period. With the expected weather scenario limited
to elevated risks of urban and river flooding, flash flooding, and
landslides will continue to impact areas already saturated by the
previous days/week rainfall activity. Daytime temperatures are
expected to stay in the mid 80s along the coastal and urban areas
of Puerto Rico and the U.S. Virgin Islands, and from the upper 70s
to low 80s across the interior.

&&

AVIATION...
(18Z TAFs)

Mainly VFR conds expected to prevail across all terminals. However,
SHRA/TSRA will continue to develop over the western interior may
lead to mtn tops obscd, VCTS are expected for JBQ/JPS thru 26/23z.
After 26/23z showers en route from the Leeward Islands/Atlc waters
may cause brief -SHRA or MVFR conds at TISX/TIST/TJSJ (and possibly
due to TSRA) thru the rest of the overnight hours; TSRA could
develop btwn 2716-23z along the southern slopes. East winds up to 14
kt with sea breeze variations, bcmg ENE around 26/22z.

&&

MARINE...

A small northwesterly swell will continue to spread across the
local waters tonight. Showers and thunderstorms will continue to
affect the local waters for the next several days as lingering
moisture from a surface trough/old frontal boundary remains over
the local area. Winds will prevail from the east and becoming
northeast on Saturday under the influence of a surface high
pressure moving off the eastern coast of the United States. A
northerly swell is anticipated to spread across the local waters
early next week deteriorating coastal and marine conditions.

&&


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

&&

$$

SHORT TERM...YZR/RC
AVIATION...CAM
LONG TERM....GRS
PUBLIC...ERG