930
FXCA62 TJSJ 130809
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
409 AM AST Sun Jul 13 2025

.KEY MESSAGES...

* Hazy conditions will continue over the region, but with minor
  concentrations of Saharan dust.

* Afternoon showers and isolated thunderstorms are expected over
  central and western Puerto Rico each day.

* A low risk of rip currents is expected today through Tuesday
  morning. By Tuesday afternoon, increasing winds will result in a
  moderate risk of rip currents along the north and east facing
  beaches of the islands.

* A tropical wave will approach the islands by the middle of the
  week, increasing moisture and the potential to observe showers
  and thunderstorms.

&&

.SHORT TERM...Today through Tuesday...

Mostly clear skies prevailed across the islands during the early
morning hours. Scattered showers were noted mainly across the
regional waters, with a few moving over land areas along the north
and east coast of PR, and across the northern USVI. Minimum
temperatures were from the mid-70s to low-80s across the lower
elevations of the islands to the mid-60s and mid-70s across the
higher elevations of Puerto Rico. The wind was light with a
northeasterly component.

A TUTT-low north of the area will continue to move west as a ridge
builds over the northeastern Caribbean on Monday and Tuesday. At
lower levels, weak trade wind perturbations are expected to reach
the islands on both days. For today, hazy skies will continue over
the region, but with lesser concentrations of Saharan dust.
Meanwhile, upper-level cirrus clouds are expected to increase over
the islands under the influence of the TUTT. A weak surface high
pressure over the central Atlantic will promote light to moderate
trade winds, but a northeasterly wind component is present. This
pattern today should keep heat indices just a few degrees lower than
previous days, and a Heat Advisory will not be issued at this
moment. Afternoon showers with isolated thunderstorms enhanced by
the upper low are expected to develop mainly over portions of the
Cordillera and western PR.

For the start of the workweek, the trade wind perturbations are
expected to enhance the early morning showers between the USVI and
eastern PR, where ponding of water on roads and in poor drainage
areas is expected. Then in the afternoon hours, the combination of
the available moisture content with daytime heating and the sea
breeze convergence will trigger convection over and downwind of the
mountain ranges of PR. Localized urban and small stream flooding is
expected with this activity and mainly in western PR. East to
southeast trades will return promoting a warming trend once again,
particularly on Tuesday.

.LONG TERM...Wednesday through Sunday...

A wet weather pattern is expected for the first half of the long-
term forecast due to the approach of a broad tropical wave into the
region. This tropical wave is anticipated to reach the islands
between Wednesday and Thursday, promoting a high moisture
environment and unsettled weather conditions. The latest
precipitable water content guidance (PWAT) has values up to 2.10
inches, suggesting a very moist environment beginning by early
Wednesday and lasting through late Thursday. Therefore, showers and
thunderstorms are likely over portions of eastern, central and
western Puerto Rico, and the U.S. Virgin Islands during this period.
After the wave passage, a drier airmass will begin to filter into
the region. Nonetheless, pockets of moisture will continue to
filter from time to time, promoting isolated to scattered showers
over the islands. From Saturday onwards, a mid-level ridge is
expected to build near the region, promoting drier conditions and
stability aloft.

Recent model guidance continues to suggest the arrival of another
pulse of high concentrations of Saharan Air layer (SAL)into the
region. This event will also help to inhibit the development of
shower across the islands. Be prepared for hazy skies, reduced
visibilities and deteriorated air quality through at least the
upcoming weekend.

Hot temperatures will remain all week across the area with maximum
temperatures reaching upper 80s to low 90s along the coastal and
urban areas each day. Heat indices are expected to rise into values
above 105 degrees Fahrenheit each day as well, mainly due to the
combination of high temperatures and high moisture. Residents and
visitors, please be aware of these conditions and plan
accordingly if planning to do outdoor activities under sun
exposure.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, TSRA over the western interior of
PR may will cause mostly VCTS at TJPS/TJBQ, and brief MVFR cigs btw
13/18z-22z. HZ due to Saharan dust will gradually diminish today.
East winds expected btw 9-14 kt with sea breeze variations and
higher gusts aft 13/14z.

&&

.MARINE...

A surface high pressure across the central Atlantic will continue
to promote moderate easterly winds across the region. Moderate to
locally fresh easterly winds are expected to return by early next
week. Therefore, small craft operators will likely be encouraged to
exercise caution. A tropical wave will approach the region by the
middle of next week, increasing moisture and the potential to observe
showers and thunderstorms.

&&

.BEACH FORECAST...

There is a low risk of rip currents across all local beaches. However,
life-threatening rip currents may still occur, especially near
groins, jetties, reefs, and piers. Always swim near a lifeguard
and follow the advice of local beach patrols and flag warning
systems.

Starting by late Tuesday, a moderate risk of rip currents will
return to the north and east facing beaches of PR, Culebra,
Vieques and the U.S. Virgin Islands, accompanied by increasing
winds. Warm to hot conditions are expected to persist through the
week, with heat index values likely exceeding 100F. Stay well
hydrated, seek shade frequently, and avoid outdoor activity during
peak sun hours.

&&

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

$$

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