641
FXCA62 TJSJ 082017
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
417 PM AST Sat Jun 8 2024

.SYNOPSIS...
A stable weather pattern is expected for the next several days
under the presence of a low to upper ridge dominating the region.
The islands will be mostly dominated by an east-southeasterly wind
flow at the surface. Under this wind pattern, a warm spell will
prevail for the next two days. As a result, an Excessive Heat
Watch is in effect for most of the coastal areas on Sunday, and
warmer conditions are expected for Monday.

&&

.SHORT TERM...Tonight through Monday:

A stable weather pattern prevailed across the islands today, with
warmer temperatures and no rainfall activity for any sector of
the island. According to some unofficial stations across the
islands, heat index values reached 112 Fahrenheit degrees across
the northwestern quadrant and between 105 to 110 Fahrenheit
degrees 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 95 F at around 1 PM AST
with a maximum heat index of 105 Fahrenheit.

The forecast remains on track. At the mid to upper levels, the
presence of a ridge will continue to provide subsidence, inducing
stable weather conditions and drier air aloft, resulting in mostly
a drying pattern with minimal or no rain activity. This pattern
in the upper level will hold for most of the period, leaving the
islands dominated by a building surface high pressure extending
from the eastern Atlantic to the Central Atlantic. This surface
feature will interact over the central Atlantic by Sunday,
inducing more east-southeasterly winds across the region. Embedded
in these winds, some brief patches of tropical moisture will
filter in, causing an increase in the potential for convective
showers in the afternoon hours each day. Although showers are
still forecasted, widespread shower activity is not anticipated.

By late Sunday 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. That said, the
islands might experience some pulses of moisture, increasing the
pesky passing showers.


.LONG TERM...Tuesday through Saturday...from previous discussion
issued at 450 AM AST Saturday June 8 2024...

A surface high pressure extending from the eastern to central
Atlantic will continue to promote southeasterly winds throughout
the upcoming week. We foresee a change in the weather pattern to
begin Tuesday afternoon into Wednesday as patches of moisture
associated with an approaching tropical wave. The latest
Precipitable Water (PW) models suggest values increasing to normal
climatological levels, around 1.6 to 1.9 inches from Tuesday
night into Wednesday. That moisture field could increase the
frequency or intensity of the showers across the regional waters
resulting in better rain chances, especially across the Caribbean
waters and portions of the islands. By Thursday, the low-level
southeasterly winds will push a drier airmass, which probably will
briefly limit rain development that day. However, at the end of
the week, models agree that additional moisture from another
surface disturbance will also reach the island along with an
upper-level trough and further enhance the chance of showers
through the weekend.

Temperature-wise, even tho temperatures should improve, limited to
elevated excessive heat risk is anticipated to continue across
lower elevations and coastal areas of Puerto Rico and the rest of
the islands.

&&

.AVIATION...
VFR conds at all terminals and en route btw islands. Few low clds
btw FL028...FL050...FL100. Isold -SHRA ovr local waters and
passages. Brief late aftn SHRA psbl ovr ctrl interior and NW PR til
23Z. SFC wnd fm SE 8-12 kts and brief gusts with some sea breeze
variations...bcmg calm to lgt/vb aft 23Z. No sig operational wx
impacts attm.

&&

.MARINE...
A surface high pressure extending from the central Atlantic into
the eastern Atlantic will continue to promote a moderate east-
southeasterly wind flow across the region. Tranquil seas will
continue for the rest of the weekend into the upcoming workweek
with seas up to 5 feet for most of the CWA local waters. From
Monday into Tuesday, a tropical wave now located just over the
Lesser Antilles might result in localized shower activity due to
strong showers.

&&

.BEACH FORECAST...

There will be a low to moderate rip current risk across the
exposed local beaches for several days. For most of the northern
local beaches, the risk will remain low for tonight.

&&

.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 Sunday morning through Sunday
     afternoon for PRZ001>003-005-007-008-010>013.

     Heat Advisory until 6 PM AST this evening for PRZ012-013.

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

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

AM...None.
&&

$$

SHORT TERM...ERG
LONG TERM....LIS
PUBLIC...RVT