Ext Marbella, Puerto Rico Weather Forecast Discussion

787
FXCA62 TJSJ 110657 CCA
AFDSJU
Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
257 AM AST Thu Sep 11 2025
.KEY MESSAGES...
* Very hot temperatures are expected to prevail in the upcoming days
  across the local islands.
* Lots of sunshine, hot temperatures, and only a few passing
  showers at times are expected across the U.S. Virgin Islands.
* Active afternoons are anticipated for the interior and western
  Puerto Rico, where the risk of urban and small stream flooding is
  elevated.
* Low to moderate concentrations of Saharan dust particles will
  continue to result in hazy skies and reduced visibilities across
  the region through at least Friday.
&&
.SHORT TERM...Today through Saturday...
A strong thunderstorm persisted most of the night over the Mona
Channel. Additionally, some light showers made it to the vicinity of
the Virgin Islands, while others reached eastern Puerto Rico.
Rainfall accumulations were not significant. Temperatures were on
the warm side for the south and east of Puerto Rico, and across the
Virgin Islands, mostly in the low 80s. Temperatures were cooler in
the mountains, mostly in the mid-60s and low 70s.
The islands in the U.S. Caribbean are in between two upper level
troughs, one to the northeast, and another now over southeastern
United States. In the middle, there is an upper level ridge. This
will act to weaken the trade winds, coming out of the SE at 10-12
kts today, and below 10 knots for Friday and Saturday. At the
surface, some Saharan dust lingers, with skies looking a bit hazy.
In general, the pattern looks seasonal in terms of moisture and
instability for the region, hence with strong diurnal heating,
another active afternoon is anticipated for the interior and western
Puerto Rico. Rainfall is not favored for eastern Puerto Rico or for
the Virgin Islands, where mostly sunny to partly cloudy skies should
prevail.
Tomorrow and on Saturday, with the upper level trough just northeast
of the region, some induced showers and thunderstorms are expected
to form over the Atlantic waters. Most of the activity should remain
over waters, but the trade winds should carry some of these showers
over the Virgin Islands, Vieques and Culebra. Flooding is not
expected, but some wet roads are likely at times. The main
difference is that with lighter winds, the rain that forms across
the Cordillera Central and western Puerto Rico should last longer,
and drift toward the coastal areas of northwestern and north-central
Puerto Rico. Also, it is likely that showers also stream from El
Yunque into portions of the San Juan metro area, where the risk for
urban and small stream flooding is elevated. Lightning and gusty
winds could also be threat within the thunderstorms. For the Virgin
Islands, some showers may also develop in the western coast of St.
Croix and St. Thomas, but the probability of precipitation is lower,
and these showers should not cause significant flooding problems,
although water surges in the drainage guts cannot be ruled out.
Last but not least, temperatures are expected to remain well above
normal through the weekend, with 925 mb values over two standard
deviation above the climatological mean. Therefore, heat indices
will impact anyone without effective cooling or adequate hydration.
The users should avoid strenuous activities outdoor, look for shade
when possible, and take plenty of breaks. Also, it is important to
look out for sensitive groups and also to keep in mind the impacts
the heat may have on pets as well.
.LONG TERM...Sunday through Thursday...
A wet pattern is on the way for the islands. An upper-level trough
northeast of the region will bring showers and thunderstorms on
Sunday. By Monday, a tropical wave will move over the islands,
bringing more activity across Puerto Rico and the U.S. Virgin
Islands.
The latest precipitable water content guidance (PWAT) indicates
values of 1.90 to 2.20 inches through late Monday. Following this, a
mass of drier air will quickly move in, bringing stable conditions
through the middle of the week. By late Tuesday and into Wednesday,
a second tropical wave will approach the U.S. Virgin Islands and
Puerto Rico. This wave, combined with moisture and instability from
a nearby upper-level trough, will result in periods of moderate to
heavy showers and thunderstorms across the region. The U.S. Virgin
Islands can expect showers and few isolated thunderstorms,
particularly during the morning hours. Then, afternoon convective
activity is expected across central and northwestern Puerto Rico
through the early evening hours. Under these conditions, there is
a limited to elevated risk for urban and small stream flooding,
as well as lightning across the islands.
The 925 mb temperature will remain above-than-normal throughout
the period. Highs will remain in the upper 80s to low 90s along
the coastal and urban areas of the islands, to the low 80s in the
higher elevations. Residents and visitors are advised to monitor
the weather conditions and plan accordingly if having outdoor
activities under sun exposure.
&&
.AVIATION...
(06Z TAFs)
Mainly VFR conditions expected to prevail through the forecast
period. SHRA will move at times across TJSJ and USVI terminals, but
impacts to operations are expected to be minimal, if any. After 17Z,
SHRA and TSRA are expected across the western Cordillera Central and
TJBQ. Periods of reduced VIS and low ceilings are anticipated. Winds
will be from the SE at 10-12 kts, with stronger gusts.
&&
.MARINE...
A surface high pressure across the central Atlantic and a front over
the western Atlantic will promote light to moderate east to southeast
winds through the end of the week. Moderate concentrations of Saharan
dust particles will be present in the area through today, slightly
decreasing visibilities.
&&
.BEACH FORECAST...
Beachgoers, there is a moderate risk of rip currents for the
northern and east-facing beaches of Puerto Rico and St. Croix
today. Additionally, isolated thunderstorms may develop each
afternoon. If you hear thunder, please move to a safer place
indoors.
The risk is expected to decrease to low by Friday and into the
weekend. Although the risk of rip currents will be low, life-
threatening currents can still occur near groins, jetties, reefs,
and piers, so exercise caution. The risk is expected to increase
to moderate again early next week.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Extreme Heat Warning from 10 AM this morning to 4 PM AST this
     afternoon for PRZ001>005-007-008-010-011.
Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for PRZ012-013.
VI...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon
     for VIZ001-002.
AM...None.
&&
$$
ERG/GRS

NWS SJU Office Area Forecast Discussion