190
FXCA62 TJSJ 272046
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
446 PM AST Thu Jun 27 2024

.SYNOPSIS...

Tonight into Friday, a high pressure system over the Central Atlantic
will strengthen over the local region, creating dry and stable
conditions across the area through at least Saturday, until the
next Wave moves in. Moisture associated to this tropical wave will
increase the shower and cloud coverage through Sunday. At this
moment the National Hurricane Center is monitoring a vigorous
tropical wave with a moderate to high chance chance of formation
in the long term. Residents in Puerto Rico and the U.S. Virgin
Islands should always stay tuned with the latest information using
official sources.

&&

.SHORT TERM...Tonight through Saturday...

In the morning hours, mostly hazy skies prevailed across the islands,
with some showers reaching the eastern half of Puerto Rico and
much lighter concentrations falling over the U.S. Virgin Islands.
Throughout the day, winds were mostly out of the east at around 10
to 15 mph, with some sea breeze variations. By the afternoon
hours, the shower and thunderstorm activity proceeded to develop
across the western to southwestern sections of Puerto Rico, where
some higher wind gusts were reported within the heaviest activity.
The rainfall accumulations at this time range from 1 to 2 inches
and around 3 inches, particularly in the southwestern sections of
Puerto Rico. Temperature-wise, they remain in the upper 80s to
mid-90s along the coastal areas and the upper 70s to low 80s over
the mountainous areas. The heat indices today stay in the 100s
along the urban and coastal areas of the islands where the heat
advisory was issued.

Tonight, expect enough surface moisture to prevail along with a
low-to-mid-level trough. Precipitable water models suggest values
going from above-normal to normal climatological levels for this
time of the year.The minimum temperatures will remain in the
upper 70s to low 80s at the coast and in the upper 60s to low 70s
over the interior.

We forecast that Saharan dust particles will diminish through the end
of the work week, but another plume of Saharan dust will reach
the area on Saturday, with concentrations of around 0.20. The
latest model guidance continues to suggest a building surface
high- pressure system over the central Atlantic, and as a result,
mostly dry and stable conditions along with easterly winds will
prevail through the early hours of Saturday when another tropical
wave will move close to the forecast area. However, with the high
pressure and the easterly winds, expect the typical afternoon
showers and thunderstorm activity across the interior and
south/southwestern sections of Puerto Rico through Friday. As
mentioned in previous discussions, an advective pattern will
prevail with passing showers across the USVI and the
east/northeast sections of PR each day. We cannot rule out urban
and small stream flooding, particularly during the afternoon hours
over western PR.

&&

.LONG TERM...Sunday through Thursday...

The long term forecast is based on the forecast trajectory of a
couple of tropical disturbance that area expected to move south
of the local area. We are currently monitoring two tropical weather
systems. The first system has a higher potential for development,
however, a high pressure area will keep it positioned well to the
south of our region. The second tropical wave is not forecasted
to develop as significantly,but models suggest it will be located
somewhat closer to the local region. While it might initially
appear that neither of these systems will have a direct impact on
our area, they will indeed indirectly affect us. Both systems
will lead to increased cloudiness and higher likelihood of rain.
Our primary concern, however, is the hazardous marine conditions
anticipated, particularly in the Caribbean Sea, due to the
forecast track of both systems. The first wave now Invest 95L is
forecast between late Monday and Tuesday and the second wave is
forecast to move south of the area between Wednesday and Thursday.

&&

.AVIATION...

(18Z TAFS)

VFR conds will prevail across terminals during the next 24 hrs.
Occasional SHRA/-SHRA will arrive thru the prd. Hazy skies with P6SM
VIS will continue due to traces of suspended dust particles. TSRA
will develop across the interior/W-PR moving across the surrounding
waters thru 28/02z. Convection will develop tomorrow, btw 28/15z-
22z, due to local effects. Expect E-winds at 14-16 kt with stronger
gusts and sea breeze variations, becoming calm to light and VRB aft
27/23z. Winds will return from the E/ENE at 15kt or more aft 28/13z.

&&

.MARINE...

A surface high pressure over the central Atlantic will promote light
to moderate east-southeasterly winds. Trade wind showers will move
across the regional waters from time to time due to a tropical wave
moving south over the Caribbean Waters. Another tropical wave now
being monitored by the National Hurricane Center, will move into the
Caribbean Sea around Monday, please actively monitor the weather
conditions during the weekend.

&&

.BEACH FORECAST...

There is moderate risk for the island of St. Croix. Elsewhere, the
risk is low.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001-003-005-
     007-008-010-011-013.

VI...Heat Advisory until 4 PM AST this afternoon for VIZ001-002.

AM...None.
&&

$$

SHORT TERM...MMC/ERG
LONG TERM....EM
AVIATION...CAM
MARINE/BEACH FORECAST...MMC
PUBLIC DESK...RVT