124
FXCA62 TJSJ 300855
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Thu May 30 2024

.SYNOPSIS...

A tropical wave will pass mainly south of the region today. A
Saharan Ar Layer will bring hazy skies on Friday. Diurnally
induced afternoon showers and thunderstorms are expected each day,
mainly across the interior and western Puerto Rico. Another
tropical wave is expected to cross the local area late in the
weekend. A wetter pattern is forecast for next week. Warm to hot
conditions expected across most lower elevations of the islands
during the next several days.


&&

.SHORT TERM...Today through Saturday...

Overnight observations from satellite and radar indicated moderate
shower activity over the local Atlantic and Caribbean waters. Some
of this activity moved inland over the eastern municipalities of
Puerto Rico, and Vieques. Doppler radar estimated rainfall
accumulations between 0.5 to 1.0 inches in Naguabo, Ceiba, Fajardo
and Vieques. Minimum temperatures were observed in the upper 70s to
low 80s along the coastal and urban areas, and in the mid to upper
60s across the mountains. East to southeasterly winds of less than
10 mph prevailed through most of the night.

Variable weather conditions are expected today due to the proximity
of a tropical wave and its associated moisture field. The latest
precipitable water content guidance continues to suggest normal to
above normal values around 2.0 inches. As the wave passes south of
the region over the Caribbean waters, an increase in moisture will
enhance the development of showers and thunderstorms in the
afternoon hours. The northwestern municipalities of Puerto Rico can
expect the most activity in the afternoon through early evening, due
to the southeasterly wind flow in combination with daytime heating
and local effects. Conditions will gradually improve as the evening
comes by. A mass of drier air is expected to filter into the region
by Friday. However, this airmass will come accompanied by moderate
concentration of Saharan dust that will last through Sunday. On
Saturday, similar weather conditions are expected with limited
shower activity.

Despite of the presence of the drier airmass, active afternoons are
expected to persist each afternoon across the interior and
northwestern portions of Puerto Rico. The risk of excessive rainfall
and lightning remains limited for the weekend. However, minor
flooding is possible with the heaviest rains.

Warm to hot temperatures will continue for the next several days
under moist east to southeasterly winds. Heat indices are expected
to range from 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...Sunday through Thursday...

There will still be some Saharan dust over the region as the
Saharan Air Layer weakens during the weekend. A tropical wave is
forecast to cross the islands on Sunday. This will bring an
increase in shower activity first across the U.S. Virgin Islands,
then spreading across Puerto Rico during the peak time of
afternoon convection. Some thunderstorms could be strong over
western PR.

For next week, a mid-to upper-level trough is expected to move
from the western Atlantic into the northeastern Caribbean, while a
deep layered ridge builds and hold just east of the Leeward
Islands. This will promote divergence aloft and a south to
southwesterly wind flow at lower levels. In addition, a surface
front associated to the upper trough will sink southwards but
should remain above 20N. However, pooling of moisture is expected
in general across the northeastern Caribbean through the long term
period with global models suggesting between 2.10-2.40 inches of
precipitable water content over the local area, peaking by
midweek.

The southerly winds and high humidity content will also promote
warm to hot conditions across the islands, particularly across St.
Croix and most coastal municipalities of PR.


&&

.AVIATION...

(06z TAFs)

Mainly VFR conds expected across all terminals. SHRA will continue
to move into from the Caribbean waters and Anegada passage and VCSH
expected at TJSJ/TIST/TISX thru 30/14z. Aftn SHRA/TSRA may cause
tempo MVFR conds at TJSJ/TJBQ btw 30/17-23z. Winds will prevail from
the ESE at 10-15 kts with higher gusts and sea breeze variations aft
30/14z.


&&

.MARINE...

A moderate east to southeast wind flow will prevail across the region
over the next few days. The next tropical wave will move far to the
south of Puerto Rico and the U.S. Virgin Islands between today and
early Friday. Thunderstorms are expected to develop once again
today, between the late afternoon and evening hours across the
western waters of Puerto Rico.


&&

.BEACH FORECAST...

A low to moderate risk of rip currents will continue today across
most beaches of the U.S. Virgin Islands and Puerto Rico. Isolated
thunderstorms are expected this afternoon across the northwest
coast of Puerto Rico.


&&

.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