171
FXCA62 TJSJ 310901
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Fri May 31 2024

.SYNOPSIS...

Short-term concerns include continued heat through the weekend,
daily afternoon showers and thunderstorms mainly across the interior
and western Puerto Rico, and the arrival of Saharan dust, contributing
to hazy skies and elevated to moderate heat risk. Wet and unstable
conditions are expected early next week.


&&

.SHORT TERM...Today through Sunday...

Calm weather conditions prevailed overnight under clear to partly
cloudy skies. Satellite and radar observations indicated showers and
isolated thunderstorms over the Caribbean waters south of Puerto
Rico. Fast moving passing showers were also observed over the
Anegada Passage, some of this showers moved inland over eastern
Puerto Rico leaving minimal accumulations. Minimum temperatures were
observed in the upper 70s to low 80s across the coastal and urban
areas, and un the upper 60s in the higher elevations.

For today, typical weather conditions will persist across Puerto
Rico and the U.S. Virgin Islands. A slight decrease in moisture
content is expected today into Saturday, with precipitable water
values between 1.75 to 1.90 inches. However, an increase in moisture
content is expected by late Saturday into Sunday due to the arrival
of another tropical wave located at 45W.

A moderate east to southeast wind flow will prevail across the
region for the next few days. Showers will continue to move over the
eastern and southeastern portions of Puerto Rico, and the U.S.
Virgin Islands during the morning hours. Then, convective activity
is once again anticipated over the northwestern quadrant of Puerto
Rico during the afternoon hours. Moderate to heavy rainfall across
these areas may result in urban and small stream flooding, river
rises, and potential mudslides. From Friday onward, a Saharan dust
plume is expected to reach the local area until at least Sunday. The
presence of this particles may suppress shower development in some
areas, bringing hazy skies across the northeastern Caribbean.

A warm temperature trend will continue for the next few days due to
temperatures well above normal in the 925 mb. Therefore, high
temperatures in combination with above-normal moisture will result in
heat indices between 104 to 111 degrees Fahrenheit along the
northern and western portions of Puerto Rico and St. Croix.
Therefore, a Heat Advisory will be in effect starting at 10 AM AST
today for the mentioned areas.

.LONG TERM...Monday through Friday...

The lingering moisture from a departing tropical wave is set to
continue promoting shower and thunderstorm activity across the
region on Monday, with some thunderstorms potentially being strong
over western PR. Following this, a wet weather pattern is expected
to unfold across the northeastern Caribbean as a mid-to-upper-
level trough moves from the northwestern to the north-central
Caribbean, while a deep layered ridge builds and holds just east
of the Leeward Islands. This will promote divergence aloft and
south-to-southwesterly wind flow at lower levels. Furthermore,
global models are indicating the development of an elongated area
of low pressure to our north/northwest through the first part of
the week. In response, moisture pooling is generally expected
across the local area through most of the long-term period, with
guidance suggesting 2.00-2.50 inches of precipitable water
content, peaking by midweek. Therefore, the risk of flooding rains
will significantly increase across all the islands.

As the southerly winds and high humidity persist, we can expect
warm to hot conditions across the islands, particularly across St.
Croix and most coastal municipalities of PR, on Monday. Afterward,
it will depend on how much cloud cover and rainfall materialize
over the islands. A drying trend is expected by Friday as the
broad surface ridge becomes the dominant weather feature.


&&

.AVIATION...

(06z TAFs)

Mainly VFR conds expected across all local terminals. Trade wind
showers will continue to move into the area during the morning
hours. VCSH expected at TJSJ/TIST/TISX thru 31/14z. A SAL will arrive
today, causing hazy skies and lowering VIS at times. Aftn SHRA/TSRA
may cause brief tempo MVFR conds at TJBQ btw 31/17-23z. Winds will
prevail from the ESE at 10-15 kts with higher gusts and sea breeze
variations aft 31/14z.


&&

.MARINE...

A moderate to locally fresh east to southeast wind flow will
prevail across the region through Saturday, becoming easterly
briefly on Sunday, and with a dominant southerly component through
midweek next week. A tropical wave will continue to move westward
across the offshore Caribbean waters and the Mona Passage today.
Increasing winds and seas are expected across the Caribbean
offshore waters. Thunderstorms are expected to develop once again
between the late afternoon and evening hours across the western
waters of Puerto Rico.


&&

.BEACH FORECAST...

A low risk of rip currents will continue today across most
beaches of Puerto Rico, St. Thomas, and St. John while a moderate
risk is expected across southwestern Puerto Rico, Vieques, and
St. Croix. The risk of rip currents is expected to remain between
low and moderate throughout the upcoming weekend.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for PRZ001-005-008-010.

VI...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for VIZ002.

AM...None.
&&

$$

SHORT TERM...GRS
LONG TERM....DSR