538
FXCA62 TJSJ 300837
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
437 AM AST Mon Sep 30 2024

.SYNOPSIS...

A Heat Advisory will be in effect today for the north and west
coastal and urban areas of Puerto Rico and St. Croix through this
afternoon. Abundant moisture and above normal temperatures will
produce scattered showers early morning and over Cordillera Central
and south Puerto Rico from late morning to late afternoon most days
through the week. A dry trend early next week as a high pressure
moves and settles over the forecast area late Sunday. There`s a high
rip current risk for the north-facing beaches of the islands.


&&

.SHORT TERM...Today through Wednesday...

A broad upper-level low has moved south of Hispaniola, and scattered
showers were observed across the local waters with isolated
thunderstorms developing over the Mona Passage through the night. A
few showers moved over land areas, leaving mostly minor rainfall
accumulations in St. Croix and eastern Puerto Rico. Minimum
temperatures were from the upper 60s across the higher elevations of
PR to the upper 70s and low 80s across the coastal sections of the
islands.

A surface high pressure over the western Atlantic just north of the
Bahamas and Tropical Depresion Joyce near 22N well northeast of the
region will promote light winds during the next couple of days.
Winds today will have a weak easterly component as a trade wind
perturbation (likely induced by the upper-low) moves from the
Leeward Islands across the region. Thereafter, winds will gradually
turn northeast to north from Tuesday to Wednesday. Therefore, today
seems to be the rainiest day of the short-term period. Shower and
thunderstorm activity will continue to increase in general today
across the local waters as the perturbation streams across the
region, and thereafter enhance the diurnal convection cycle over the
islands, with the strongest activity developing in the afternoon
hours over the interior and western PR. Flooding is expected and
some thunderstorms could produce strong gusty winds. In addition,
hot temperatures are expected once again before the onset of
afternoon showers and a Heat Advisory (NPWSJU) is in effect for
portions of northern and western PR, and St. Croix.

The precipitable water (PWAT) content is expected to peak today
between 2.00-2.20 inches, with a drying trend expected from late
Tuesday and Wednesday as the layered ridge over Bahamas sinks
southwards over Hispaniola and into the local area. PWAT is expected
to bottom out between 1.40-1.70 inches by early Wednesday morning.

.LONG TERM...Thursday through Monday...

On Thursday, a weak mid-level high pressure over the western
Atlantic will sink further into the north-central Caribbean.
Additionally, 500 mb temperatures will warm between -3 and -4
degrees. This could potentially inhibit convective activity across
the forecast area. However, moisture content is expected to
increase. Model guidance suggests precipitable water content will
surge above 2.0 inches, even reaching up to 2.2 inches, which is
near to above the climatological normal. Therefore, expect shower
activity across interior Puerto Rico with a few very isolated
thunderstorms.

Afterwards, winds at the surface will remain light from ENE until
Saturday due to a ridge to our west/northwest and a tropical cyclone
over the far Tropical Atlantic, becoming variable by Sunday onwards.
With a surge in low-level moisture and a mid-to-high level trough
moving into the northeastern Caribbean by the end of this week into
the weekend, shower and thunderstorm activity will increase once
again mainly over the interior and southern sections of the islands
for the forecast period. Slow moving showers will enhance rainfall
accumulations across the area. Hence, a limited to elevated flooding
risk can be anticipated. Ponding of water in roadways and poorly
drained areas are likely, with urban and small stream flooding
across interior Puerto Rico during the afternoon hours.

Then, a mid-level ridge will move eastward and settles over the
forecast area by Monday inhibiting shower activity for the most
part. The combination of limited shower activity, clear skies, and
subsidence aloft will promote hot temperatures for early next
week. Limited to elevated heat risk will prevail for coastal and
urban areas of PR and USVI.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions expected across all terminals through the
forecast period. However, diurnally induced afternoon SHRA/TSRA
could lead to tempo MVFR to brief IFR conds at TJPS/TJBQ btw 30/18z-
22z. VCTS is possible across the rest of the terminals. Easterly
winds expected up to 12 kt with sea breeze variations aft 30/14z.

&&

.MARINE...

A high pressure system over the western Atlantic will maintain
light to gentle northeast to easterly winds. Seas will remain around
3 to 5 feet over the next few days. Showers and thunderstorms remain
possible across the regional waters through the week.


&&

.BEACH FORECAST...

Nearshore buoys are indicating breaking waves of 6-8 feet with
swell action continuing through at least this afternoon.
Therefore, a High Rip Current Risk (CFWSJU) is in effect for the
northeast to northwestern beaches of Puerto Rico, including
Culebra.



&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through this afternoon for PRZ001-002-005-
     008-010-012.

     Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001-005-008-010.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ002.

AM...None.
&&

$$


SHORT TERM/AVIATION...DSR
LONG TERM/MARINE...MNG/CVB