042
FXCA62 TJSJ 090930
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
530 AM AST Sun Jun 9 2024

.SYNOPSIS...High pressure extends out of the central Atlantic and
across the Atlantic waters just north of the local area. With
limited moisture this is bringing warmer than usual temperatures
that will gradually cool through Friday. Some limited showers will
be possible, with a tropical wave passing to our south and
moisture from an old frontal boundary entering into the area on
Thursday.


&&

.SHORT TERM...Today through Tuesday...

An overnight radar and satellite imagery analysis indicated areas of
clear to partly cloudy skies as some high clouds moved across the
region. Some showers generated variable cloudy skies and rainfall
accumulations of up to a tenth of an inch across portions of eastern
Puerto Rico, Vieques, and the local waters. Overnight minimum
temperatures stayed in the lower 80s across coastal areas of the
metro area, northeastern, and southwestern Puerto Rico. Across the
mountains, temperatures dropped to the upper 60s.

Today we are expecting another day with warm to hot temperatures.
Note that an Excessive Heat Warning (NPWSJU) is in effect today for
the lower elevations and coastal areas of mainland PR, while eastern
PR, Culebra, Vieques, St Croix, St Thomas, and St John have a Heat
Advisory. An Excessive Heat Watch is also in effect for Monday,
between 9 AM AST and 6 PM AST, as hot conditions will likely
return.

The general weather pattern will continue to be dominated today by
the presence of a ridge at the mid to upper levels and a surface
high pressure extending from the eastern Atlantic to the Central
Atlantic. This will continue to provide subsidence, inducing stable
weather conditions and drier air aloft, mostly resulting in
a drying pattern with minimal to no rain activity. The latest
Precipitable Water (PW) models suggest values around normal to
below normal climatological levels, around 1.5 to 1.9 inches
during the short-term period. Tonight into Monday, model guidance
continues to suggest the passage of a tropical wave well south of
the islands, leaving the bulk of the moisture over the Caribbean
Sea. As a result, every day of the period, isolated to scattered
afternoon convection may occur due to local effects, especially
across northwestern Puerto Rico during the afternoon hours.
Furthermore, patches of clouds moving in along the windward areas
may bring brief passing showers. Also, due to the warm sea surface
temperatures, nighttime showers may form over the adjacent waters
and occasionally move inland like the last few days.

.LONG TERM...Wednesday through Sunday...

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...
(06Z TAFs)

Mainly VFR conditions prevail across all terminals during the
period although TJNR will have some MVFR in the morning. TJBQ may
experience some VCSH around 18Z. Light to calm and variable winds
will turn from the E-ESE at 10-15 knots between 09/13-22Z,
accompanied by higher gusts and sea breeze variations.

&&

.MARINE...Seas will generally run 2 to 4 feet in the open waters
around the island and less than 2 feet in protected waters. The
wave passage on Tuesday night will boost seas up to 6 feet in the
southwest corner of the forecast area.


&&

.CLIMATE...Very warm temperatures have continued with the high of
95 and the low of 81 on Sunday both being the second warmest on
record.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning from 9 AM this morning to 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 from 9 AM this morning to 6 PM AST this evening
     for PRZ002-012-013.

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

     Heat Advisory from 9 AM this morning to 6 PM AST this evening
     for VIZ001-002.

AM...None.
&&

$$

SHORT TERM...YZR
LONG TERM....WS
AVIATION...YZR