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430
FXCA62 TJSJ 290906
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
506 AM AST Wed May 29 2024

.SYNOPSIS...

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Warm to hot conditions will persist today across the region. A
Heat Advisory will be in effect today for the north and west coast
of Puerto Rico, including St. Croix. Moisture content is expected
to remain normal to above normal, enhancing the potential for
afternoon convective activity across northwest Puerto Rico. A
tropical wave is expected to approach the region by Thursday,
however, the bulk of moisture should remain over the Caribbean
waters. Drier air is expected to filter into the area by the end
of the workweek, accompanied by Saharan dust particles.
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&&

.SHORT TERM...
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Today through Friday...

Satellite and radar data indicated thunderstorms developing across
the Atlantic and Caribbean waters through early morning hours. Some
of this activity moved over eastern PR, and the Doppler radar
estimated over an inch of rain across el Yunque area. Minimum
temperatures were from the mid 60s across the higher elevations to
the upper 70s and low 80s across the lower elevations of the
islands. A Saharan Air Layer is weakening and this should allow for
moisture to increase slightly across the region today, but hazy
conditions should return once again on Friday.

Moisture content is expected to remain at normal to above normal
levels through Thursday, when a tropical wave moves across the
Caribbean waters. This will aid in the development of showers and
thunderstorms across the region. A drier air mass with suspended
Saharan dust will follow on Friday, but the local effects combined
with the available low level moisture will trigger afternoon showers
and isolated thunderstorms once again across western PR.

In addition, warm to hot temperatures are expected through the short
term period under moist east to southeasterly winds. 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, there is a Heat Advisory (NPWSJU) in effect
for today across these areas.

.LONG TERM...Saturday through Wednesday...

A surface high pressure in the central Atlantic will promote south
southeasterly winds through much of the long-term-period. Plenty of
abundant tropical moisture moving into the local area will help
to maintain a wet and unstable pattern across the islands. The
latest Precipitable Water Content analysis (PWAT) suggest values
of 2.3 to 2.5 inches between Sunday through Monday. This is in
response of the development of a surface trough west of the region
that will enhance the shower and thunderstorm potential across
Puerto Rico and the U.S. Virgin Islands. Sufficient moisture in
combination with daytime heating and local effects, will lead to
convective activity across the central interior and northwestern
portions of Puerto Rico during the afternoon hours. Therefore,
there is a limited to elevated risk of isolated flash flooding,
urban and small stream flooding, river rises, and mudslides. By
Tuesday into Wednesday as the surface trough lingers north of the
area, moisture from the Caribbean waters will continue to be
lifted and moved over the islands. Winds are expected to veer from
the south by Tuesday in response to the combination of the
surface trough and a approaching tropical wave. With this scenario
the potential for moderate to heavy rainfall and isolated
thunderstorms remains high. Despite the anticipated weather
scenario, warmer to hot temperatures are expected each day.
Daytime temperatures are expected to reach the upper 80s to low
90s. Meanwhile, overnight temperatures will remain in the upper
70s to low 80s along the coastal and urban areas of the islands.
Heat indices may reach the mid to upper 100s during the period,
especially during the mid-morning to early afternoon hours.
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&&

.AVIATION...
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(06z TAFs)

Mainly VFR conditions expected. However, SHRA en route
from the Leeward Islands could move at times thru 29/12 across
TIST/TISX. Also, diurnally induced afternoon SHRA/TSRA may cause
tempo MVFR conds at TJSJ/TJBQ btw 29/17z-21z. Winds will increase
from the east at 10-15 kt with higher gusts and sea breeze
variations after 29/14z.
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&&

.MARINE...

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A moderate east to southeast wind flow will prevail across the region
over the next few days. Showers and isolated thunderstorms associated
with the trailing moisture from a tropical wave which exited the region
and a surface trough just east of the area us will continue to affect
the regional waters and local passages. The next tropical wave,
located near the Lesser Antilles, is forecast to approach the
regional waters later today, with the bulk of associated moisture
expected to remain well to the south across the Caribbean Sea.
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&&

.BEACH FORECAST...

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There is a moderate risk of rip currents across the northwestern
beaches of Puerto Rico, and the beaches of St. Croix. Elsewhere,
there is a low risk. Moderate to heavy showers and isolated
thunderstorms are possible each afternoon mainly across the
northwestern waters of Puerto Rico.
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&&

.SJU WATCHES/WARNINGS/ADVISORIES...
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PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ005-008-010.

VI...None.
AM...None.
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&&

$$

SHORT TERM...DSR
LONG TERM....GRS
AVIATION...DSR