492
FXCA62 TJSJ 240839
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
439 AM AST Mon Jun 24 2024

.SYNOPSIS...
The arrival of a tropical wave today will bring showers and
thunderstorms across the area, especially during the afternoon. A
thick plume of Saharan dust will bring hot and hazy conditions
from tomorrow through Thursday morning, then a trade wind pattern
with advection showers and afternoon convection will prevail. Hot
temperatures are expected through the week with a Heat Advisory in
effect for northern and western Puerto Rico and a watch for
tomorrow afternoon for all the coastal sections of PR and the
USVI.

&&

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

Passing showers have been moving across Puerto Rico and the United
States Virgin Islands during the night hours. The strongest activity
was observed early in the night, across northeastern Puerto Rico,
with lightning detected. All this rain is related to a tropical wave
near the Lesser Antilles. The field moisture is evident in the
satellite-derived precipitable water product.

As the wave progresses today, moisture value will remain well above
the climatological value for this time of year, meaning that
conditions will be favorable for showers and thunderstorms. It will
be gusty too, with a southeast breeze at 15 to 25 mph. The risk for
flooding will be elevated, with lightning and gusty winds
anticipated with the thunderstorms.

Once the wave departs, a dense Saharan Air Layer follows, so
conditions will dry out later this evening. Hazy skies and hot
temperatures are anticipated for Tuesday and Wednesday, with only a
few showers reaching the islands at times. Afternoon convection will
remain possible for western Puerto Rico, but conditions aloft will
not favor widespread nor strong rainfall accumulation.

&&

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

Through early in the weekend, there will be a mid-to upper-level
ridge across the northeastern Caribbean. Its still possible that
afternoon showers will form across the western sections of Puerto
Rico. Instability will slightly increase from late Thursday and
Friday as an induced low-level trade wind perturbation streams
across the local area raising moisture content that will increase
the chance of isolated thunderstorms and showers.

A trade wind pattern due to an established surface high across the
Atlantic basin will drag tropical moisture into the islands through
the weekend into next week. According to global model guidance, PWAT
values will fluctuate from 1.70 to 2.10 inches, just above seasonal
climatological values for the region. That moisture, along with
diurnal heating, will promote the development of afternoon showers
and isolated thunderstorms each day across the western interior
sections of Puerto Rico. The arrival of drier air on Monday may
reduce the chance of showers, however do still expect a typical
seasonal pattern of passing showers and afternoon convection for the
start of the following week.

&&

.AVIATION...

(06Z TAFs) SHRA and isolated TSRA from a tropical wave will move
across the area today, reaching the terminals at times. The activity
will be strongest after 15Z, with periods of reduced VIS and low
ceilings expected. Winds will be from the southeast from the
surface through FL150, at 14-24 kts.

&&

.MARINE...

A surface high pressure over the central Atlantic will promote
light to moderate southeasterly winds. Trade wind showers will move
across the regional waters from time to time. The next tropical wave
will approach the local islands from late tonight through Monday.
Increasing winds and showers with thunderstorms are expected through
tonight across the local waters. Hazy skies are expected from
Tuesday through Thursday due to Saharan dust.

&&

BEACH FORECAST...

There is a low to moderate risk of rip currents across PR and the
USVI. Showers and isolated thunderstorms are possible across the
coastal areas of the USVI and eastern PR during the morning hours,
and across the west/northwest coast of PR during the afternoon.
The afternoon thunderstorms could produce frequent lightning and
gusty winds.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 2 PM AST this afternoon
     for PRZ001-005-008-010-011.

     Excessive Heat Watch from Tuesday morning through Tuesday
     afternoon for PRZ001>003-005-007-008-010-011.

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

AM...None.

&&

$$

SHORT TERM...ERG
LONG TERM....RC