235
FXCA62 TJSJ 010848
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
448 AM AST Sat Jun 1 2024

.SYNOPSIS...

Expect the hazy skies and warm weather conditions to prevail
through the weekend and early next week. We anticipate the
typical afternoon across western and northwestern Puerto Rico.
Wet and unstable conditions are expected early next week due to
an approaching tropical wave. Improving conditions are foreseen
from Friday onwards.

&&

.SHORT TERM...Today through Monday...

Hot temperatures are expected to continue through the rest of the
short term period. Heat indices are expected to range from 104 to
112 degrees Fahrenheit, mainly along the lower elevations of western
and northern Puerto Rico, and St. Croix. Therefore, another Heat
Advisory (NPWSJU) was issued across these areas, and will likely be
issued once again on Sunday and Monday. Hazy skies will continue
today and through at least early Sunday as the area remains under
the influence of a Saharan Air Layer with moderate to high
concentrations of Saharan dust. This drier air mass will limit
shower activity in general, but diurnally induced streamers
developing off the USVI and smaller islands and possible isolated
thunderstorms could still develop once again this afternoon over
western PR.

On Sunday and Monday, a gradual increase in moisture content is
expected as a tropical wave streams across the islands and a broad
surface trough develops west of the region. The precipitable water
content is forecast to increase from around 1.50 inches today to
near 2.50 inches by late Sunday into Monday morning under a moist
southeast wind flow. Therefore, the risk for flooding rains will
increase across the USVI and most areas of Puerto Rico. Residents
and visitors in PR should avoid activities in small streams and
waterfalls due to the risk of sudden water rises across the area
rivers.

&&

.LONG TERM...Tuesday through Saturday...

The inherited forecast remains unchanged. The latest model
guidance suggests Precipitable Water(PW) values staying in the
75th percentile or above normal values for this time of the year
as lingering moisture from a departing tropical wave continues to
promote showers and thunderstorm activity across Puerto Rico and
the U.S. Virgin Islands with some thunderstorms potentially being
strong over western PR. We foresee a wet weather pattern unfolding
across the northeastern Caribbean as a mid-to-upper-level trough
moves from the northwestern to the north-central Caribbean while a
deep layered ridge builds and holds just east of the Leeward
Islands. This weather pattern will promote divergence aloft and
south-to-southwesterly wind flow at the surface. As mentioned in
previous discussions, an elongated area of low pressure will
develop to our north/northwest, particularly by the first part of
the week. In response, moisture pooling is generally expected
across the local area through most of the long-term period, with
guidance suggesting 2.00-2.50 inches of precipitable water
content, peaking from Tuesday into midweek. Therefore, the risk of
flooding rains will significantly increase across all the
islands. Nonetheless, with the persistent southerly winds and high
humidity, we can expect warm to hot conditions across the
islands. However, it will depend on how much cloud cover and
rainfall materialize over the islands.

A drying trend is expected by the end of the workweek and early
in the weekend as a broad surface ridge becomes the dominant
weather feature. Overall, expect wet and somehow unstable weather
conditions to prevail through Thursday and improve weather
conditions from Friday onwards.

&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, SHRA/TSRA is expected to develop
btw 01/17z-21z in and around TJBQ, causing tempo MVFR conds. HZ due
to Saharan dust will continue through early Sunday, this is causing
false cigs at TISX. ESE winds expected at 10-15 kt with higher gusts
and sea breeze variations aft 01/14z.

&&

.MARINE...

A moderate east to southeast wind flow will prevail across the
region today, becoming easterly briefly on Sunday, and with a
dominant southerly component through midweek next week. Thunderstorms
are expected to develop during the weekend between the late
afternoon and evening hours across the western waters of Puerto Rico.
A wetter pattern is anticipated by Sunday into early next week as
the next tropical wave will approach the region.

&&

.BEACH FORECAST...

A low risk of rip currents will continue today across most
beaches of Puerto Rico, Culebra, St. Thomas, and St. John while a
moderate risk is expected across southwestern Puerto Rico,
Vieques, and St. Croix. The risk of rip currents is expected to
remain between low and moderate throughout the upcoming weekend. A
high risk of rip current is possible across the beaches in Saint
Croix.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for PRZ001-005-008-010.

VI...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for VIZ002.

AM...None.
&&

$$

SHORT TERM/AVIATION...DS
LONG TERM/MARINE/BEACH FORECAST....MMC