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736
FXCA62 TJSJ 252042
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
442 PM AST Sat May 25 2024

.SYNOPSIS...

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We anticipate showers and thunderstorms to develop across
portions of Puerto Rico, particularly the central, north, and west
sections each afternoon. Although a ridge aloft is expected to
build during the workweek, plenty of moisture will continue to
prevail. As a result, any prolonged period of showers and
thunderstorms will result in urban and small-stream flooding. The
driest day in the short term, Sunday. The aforementioned available
moisture and the prevailing east to east southeast winds will
promote heat index values that can affect individuals sensitive to
heat by tomorrow.
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&&

.SHORT TERM...
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Tonight through Monday...

In the morning, cloudy skies and calm weather conditions prevailed
across Puerto Rico and the U.S. Virgin Islands. By the afternoon,
showers started to develop along the interior and western
municipalities of Puerto Rico. Temperature-wise, they remained in
the upper 80s to low 90s along the coastal and urban areas, while
over the higher elevations, they stayed in the upper 70s to low
80s. The prevailing wind flow was out of the east-southeast
throughout the day.

Overnight, expect some showers to develop along the eastern half of
Puerto Rico and Saint Thomas. Minimum temperatures should remain
in the upper 70s to low 80s along the coast and in the 70s across
the mountains. Wind-wise, the wind flow is expected to stay from
the east-southeast.

On Sunday, we foresee mostly stable, warm weather conditions along
with some hazy skies, particularly in the morning hours. The
deep-layered trough will continue to weaken while the mid-
levelridge remains aloft. Moisture content will decrease
slightly, remaining belownormal to near-normal levels. Despite
this decrease inmoisture,subsidence aloft will exacerbate warmer
temperatures across the islands, withheat index values reaching
hazardous levels.With these conditions, it islikely that we meet
HeatWarning criteria, particularly across northern coastal
municipalities. Nonetheless, by the afternoon, we continue to
forecast the typical short-lived afternoon convection over the
northwestern quadrant. The latest model guidance continues to
suggest an increase in instability from

Sunday night into Monday as the leading edge of the tropical wave
approaches the region. This will lead to numerous showers
scattered over eastern Puerto Rico and the smaller islands by
early Monday, as well as deep convective activity across the
region, especially across western Puerto Rico in the afternoon.
Consequently, there could be an elevated risk of flooding in the
area once again. We encourage first responders, citizens, and
visitors to continue to monitor the forecast for any updates.
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&&

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

Although the ridge aloft will hold through the forecast cycle, plenty
of moisture will continue to prevail without any erosion expected
in the midterm. In fact, the latest guidance suggested precipitable
water values exceeding 2.0 inches through at least midweek.
Moisture may decrease somewhat by the end of the workweek into the
weekend and remain trapped below 700 MB.

At lower levels, easterly winds will prevail on Tuesday, becoming
more southeast Wednesday and onwards as a surface high relocates
across the central Atlantic. Under this evolving pattern, trade
wind showers will continue to affect windward locations from time
to time, with locally induced afternoon showers expected across
western Puerto Rico each day. With GDI values greater than 25
expected much of the week, diurnal heating and sea breeze
convergence, isolated to scattered thunderstorms, are expected
each afternoon. Therefore, urban and small stream flooding is
expected each afternoon, mainly across central and western areas
of Puerto Rico and the San Juan Metro Area. In addition, available
moisture and southeast winds will promote heat index values that
can affect individuals sensitive to heat.

At this time, the bulk of African Dust will remain south of the
area for much of the week. Nevertheless, some may reach the area
by midweek.
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&&

.AVIATION...

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(18Z TAFs)

Mainly VFR conditions expected to prevail across all terminals.
However, SHRA/TSRA over the interior and western PR may cause tempo
MVFR conds at TJBQ, and mostly VCSH/VCTS at TJSJ/TJPS thru 22z. Low-
level winds will continue ESE up to 11 kt.
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&&

.MARINE...

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An east to east southeast wind flow will continue to prevail across
the local waters over the next few days. Weather conditions will
improve on Sunday. Nonetheless, shower and thunderstorm activity is
expected Sunday night into Monday with the next tropical wave
passage.
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&&

.BEACH FORECAST...

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Seas will remain below 5 feet across much of the regional waters.
Therefore, there is a low risk of rip currents across the local
beaches of Puerto Rico and the U.S. Virgin Islands.
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&&

.SJU WATCHES/WARNINGS/ADVISORIES...
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PR...None.
VI...None.
AM...None.
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&&

$$

SHORT TERM...MMC/ICP
LONG TERM....OM
AVIATION...DS
PUBLIC DESK...LIS