643
FXCA62 TJSJ 092013
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
413 PM AST Sun Jun 9 2024

.SYNOPSIS...
Warm conditions will persist through tomorrow, and an Excessive
Heat Watch will be in effect across all coastal areas of Puerto
Rico and the US Virgin Islands. By Wednesday, a tropical wave will
move over the Caribbean Waters, increasing moisture content and
the potential for showers and warmer conditions. Tranquil marine
conditions should prevail for the next five days.
&&

.SHORT TERM...Tonight through Tuesda....

Similar to the previous days, stable weather conditions prevailed
across the islands under the continued warmer trend, with no
rainfall activity in any sector of the island. According to some
unofficial stations across the islands, heat index values reached
112F in the northwestern quadrant and between 105F to 110F in
the north-central areas of Puerto Rico. According to the official
climate site at the Luis Munoz Marin Airport in Carolina, the
maximum temperature reached 93F around 1 PM AST, with a maximum
heat index of 108F.

The short-term forecast remains on track. The islands will be
dominated mainly by a mid-level ridge that will continue to
induce stable conditions. At the surface, a broad area of high
pressure extending from the eastern to the central Atlantic will
result in east-southeasterly winds over the CWA. Under this wind
pattern, the islands will continue to experience a warmer trend,
with heat indices between 100F to 112F across all coastal areas
and urban sections. Given the expected conditions, an excessive
heat watch is in effect for all coastal areas. Although the heat
watch/advisory and warning might not be in effect for some
interior municipalities, heat indices resulting in heat exhaustion
are possible, especially over San Sebastian, Lares, Sabana
Grande, and areas near Caguas. Regarding shower development, the
southeasterly wind flow can drag pockets of tropical moisture
across the region. Although no widespread shower activity is
expected, the available moisture, combined with local and diurnal
effects, might produce one or two showers over the interior
mountains.

Looking ahead to Tuesday, winds will continue from the southeast
as the surface ridge remains in the central Atlantic, extending
into the Western Atlantic. A tropical wave will move northwestward
over the Caribbean Waters, increasing moisture content across the
islands. This will lead to a variable day, with warmer conditions
in the morning and early afternoon, followed by localized
convection in the afternoon.

.LONG TERM...Wednesday through Sunday...from previous discussion
issued at 530 AM AST Sun Jun 9 2024...

A tropical wave will pass just south of the area Tuesday night and
Wednesday and will be enhanced somewhat by the passage of a weak
upper level trough to the north Tuesday night. Then high pressure
aloft intensifies over the Western Caribbean and pushes the
remnants of an old frontal boundary into the area from the
northeast with its accompanying moisture. Temperatures will
rebound on Saturday as surface winds return to a southeasterly
flow. Thunderstorms will again become possible Wednesday and
Friday over portions of the area and especially the western
interior. The influx of Saharan dust will continue through the
period bringing hazy skies and visibilities of 8 to 15 miles

&&

.AVIATION...
VFR conds at all terminals and en route btw islands. Few cld nr
FL030...FL050...FL090. Mstly Isold SHRA ovr local waters durg prd
and psbl ovr ctrl Mtn range and NW section of PR til 09/23Z. SFC wnd
fm SE 10-15 kts and brief gusts with some sea breeze variations...
bcmg calm to lgt/vb aft 09/23Z. No sig operational wx impacts attm.


&&

.MARINE...
A surface high pressure over the central Atlantic will continue to
result in a moderate southeasterly wind flow over the CWA. As a
result, local waters will experience seas up to 5 feet or less and
east-southeasterly winds up to 15 knots. Similar marine conditions
will prevail for the next several days. There is a low risk of rip
currents across all the coastal beaches of Puerto Rico tonight.
The rip current risk will remain low to moderate over the next
several days.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning until 6 PM AST this evening for PRZ001-
     003-005-007-008-010-011.

     Excessive Heat Watch from Monday morning through Monday
     afternoon for PRZ001>003-005-007-008-010>013.

     Heat Advisory until 6 PM AST this evening for PRZ002-012-013.

VI...Excessive Heat Watch from Monday morning through Monday
     afternoon for VIZ001-002.

     Heat Advisory until 6 PM AST this evening for VIZ001-002.

AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM....LIS
PUBLIC...GRS