National Weather Service Today's Weather Impact Levels

177
FXCA62 TJSJ 011705
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
105 PM AST Tue Jul 1 2025

.KEY MESSAGES...

* Trade wind showers will increase tonight across the islands.

* Breezy winds will sustain choppy seas and maintain a moderate
  risk of rip currents along exposed beaches over the next few
  days.

* A tropical wave is forecast to increase shower activity by
  Friday. However, a strong Saharan Air Layer with moderate to
  high concentrations of Saharan dust is expected to move with the
  wave into the weekend.

&&

.SHORT TERM...Tonight through Thursday...

Sunny to partly cloudy skies prevailed across the islands throught
the day. Afternoon showers were developing over the southwestern
quadrant of Puerto Rico, and streamers were developing downwind
of the U.S. Virgin Islands. Additional showers are expected later
this evening and tonight as a wind surge with showers embedded in
the trades reach the local area. Maximum temperatures were from
the mid-80s to the low 90s across the lower elevations of the
islands, and from the mid-70s to low 80s across the higher
mountains of Puerto Rico. The wind was from the east to northeast
between 15 and 20 mph with sea breeze variations and higher gusts
across coastal areas.

A mid-level ridge north of the area will continue to move west and
away of the local area today, while a trade wind perturbation
bring an additional moisture content through Wednesday morning.
This will cause mostly passing showers across the USVI and eastern
sections of PR. Thereafter, a surface high pressure will build
over the central Atlantic and winds will turn more ESE through at
least Thursday. Overall fair weather conditions are expected for
the rest of the short-term period. However, diurnally induced
afternoon showers are expected to develop each day over western
PR. A limited heat risk is expected across most coastal areas as
daytime temperatures reach the low 90s and the absence of Saharan
dust will cause relative humidities to increase in general across
the western, northern, and eastern sections of the islands.


.LONG TERM...Friday through Tuesday...

/From Prev Discussion issued at 432 AM AST Tue Jul 1 2025/

A weak tropical wave will approach the islands on Friday. The bulk
of the wave will remain over the Caribbean Sea, but enough
moisture should trigger some showers over the Virgin Islands and
Puerto Rico, with stronger convection developing across western
Puerto Rico in the afternoon. Just like the last wave that moved
over the region, this one also comes with a lot of Saharan dust,
so skies will be hazy late on Friday and on Saturday. Later on the
weekend and early next week, a series of surface troughs will
also move into the region, but they will also be embedded in
Saharan dust. The pattern aloft will not favor deep convection,
but occasional showers will move into the islands at times, with
additional showers and isolated thunderstorms each afternoon
across the west. The winds will be driven by a surface high
pressure over the eastern Atlantic, at 10 to 16 kts. It will be
hot too, as it is expected for July, with heat indices above 102
degrees along all coastal and urban areas in the region.


&&

.AVIATION...

(18Z TAFS)

VFR conditions are expected to prevail across all terminals
through the period. However, quick passing -SHRA will move at
times across the USVI/Eastern PR terminals during the night. This
may cause brief MVFR conds. The 01/12z TJSJ sounding indicated ENE
winds up to 26 kt blo 4000 ft.


&&

.MARINE...

Mariners can expect choppy seas across the local Atlantic and
Caribbean waters due persistent moderate to fresh easterly winds.
A weak tropical wave is forecast to move over the local waters on
Friday, increasing shower and thunderstorm chances. Saharan dust
will follow the tropical wave, with hazy skies returning quickly
through the weekend.


&&

.BEACH FORECAST...

A moderate risk of rip currents (life-threatening rip currents
are possible in the surf zone) are expected for most northern,
east, and southern beaches of Puerto Rico, as well as for beaches
of Culebra, Vieques, southern St. John, southern St. Thomas and
all but western St. Croix.

Life-threatening rip currents often occur in the vicinity of
groins, jetties, reefs, and piers. Up to a moderate risk of rip
currents will remain for most of the period.


&&

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

$$

DSR/MMC

NWS SJU Office Area Forecast Discussion