598
FXCA62 TJSJ 221715
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
115 PM AST Fri Aug 22 2025

.KEY MESSAGES...

* Invest AL90 will remain northeast/north of the area. However,
  the tropical wave axis will cross the islands overnight, turning
  winds southeasterly and increasing shower activity across the
  USVI and eastern sections of PR.

* Another hot day is expected on Saturday due to the combination
  of the increasing moisture and the southeasterly winds. A Heat
  Advisory will likely be issued for most coastal and urban areas
  of the lower-elevations of Puerto Rico and the U.S. Virgin
  Islands.

* Swells from distant TC Erin and AL90 will promote life-
  threatening rip currents, rough surf conditions, and Small Craft
  Advisory conditions during the weekend into early next week.


&&

.SHORT TERM...Rest of today through Sunday...

Sunny to partly cloudy skies prevailed across Puerto Rico and the
U.S. Virgin Islands through the morning hours. However, by noon
streamers were developing downwind of the USVI, leaving mostly
minor rainfall accumulations. Additional shower development as
well as isolated thunderstorms are expected to develop over
portions of the Cordillera and south/southwestern PR this
afternoon. High temperatures were from the upper 80s to low 90s
across the lower elevations of the islands. The wind was from the
northeast between 14 to 18 mph with locally higher gusts at
times.

The bulk of moisture associated to AL90 is now expected to remain
mainly north and away of the local area. However, as winds shifts
from the southeast, a band of moisture will move across the local
area from the Caribbean waters. This will enhance the early
morning scattered shower activity between the USVI and eastern
PR, followed by better organized afternoon convection over
portions of the interior and northwestern PR. As moisture remains
high over the area and winds prevail from the southeast, another
hot day is expected on Saturday, and Heat Advisory conditions will
likely prevail across PR and the USVI. A drier air mass is
expected to filter on Sunday as a Saharan Air Layer moves from the
tropical Atlantic. This should cause mostly hazy conditions and
limit the development of showers in general across the islands.


.LONG TERM...Monday through Friday...

/FROM PREV DISC ISSUED AT 443 AM AST Fri Aug 22 2025/

Weather conditions will start to improve next week, as moisture
associated with the tropical wave (Invest 90L) monitored by the
National Hurricane Center (NHC) continues to move north and away
from the region. The forecast continues on track with the
positioning of an upper-level trough north of the area by Monday,
however, the islands will not be under the most favorable side of
the trough. At the low levels, a drier air mass will filter into the
area along with a Saharan Air Layer (SAL) with low to moderate
concetrations of Saharan dust. Given the expected scenario, hazy
skies, reduced visibilities, poor air quality and limited showers
are anticipated through at least Tuesday. However, late afternoon
convective activity  with showers and few isolated thunderstorms are
possible across the western municipalities of Puerto Rico each
afternoon.

By mid-week, winds will shift from the south southeast in response
to a strong surface high pressure in the central Atlantic and a long
wave polar trough exiting the eastern coast of the United States.
This will lift moisture associated with a tropical wave (Invest
99L) from the Caribbean Sea. Under this pattern, an increase in
showers are anticipated across Puerto Rico and the U.S. Virgin
Islands through the end of the workweek. The 925 mb temperatures
will remain above-normal climatological values for most of the
period. Highs will continue to reach the upper 80s to low 90s each
day along the coastal and urban areas of the islands. Heat
indices will rise up to the mid to upper 100s, due to the
available moisture and southerly winds. Residents and visitors are
advised to monitor the weather updates and plan accordingly if
having outdoor activities under sun exposure.


&&

.AVIATION...

(18z TAFs)

Mainly VFR conditions expected early in the fcst period. However,
tempo MVFR to brief IFR conds are possible at TJPS thru 22/22z.
Thereafter, -SHRA and iso TSRA are expected to increase from the
Anegada Passage/Caribbean waters through early Sat morning. This
may cause tempo MVFR conds at TISX/TIST btw 23/00z-10z, and across
the PR terminals from 23/12z-18z. The 22/12z TJSJ sounding
indicated NE winds up to 19 kt blo FL100. On Saturday morning,
winds will turn ESE at 8-12 kt.


&&

.MARINE...

Small Craft Advisory conditions due to seas building to around 7
and 8 feet are expected across the Atlantic waters and passages
from late Saturday through at least early Tuesday. A tropical wave
just east of the Anegada Passage will increase shower and isolated
thunderstorm activity tonight into Saturday morning. Hazy skies
are expected on Sunday and Monday due to Saharan dust. Moderate
to locally fresh northeasterly winds today will shift from the
southeast through the weekend.


&&

.BEACH FORECAST...

Long period swells from distant TC Erin will gradually fill across
the Atlantic coastlines of the islands for the next few days. This
will promote life-threatening rip currents and rough surf
conditions across the northern exposed beaches of the islands,
particularly from Sunday to Tuesday. However, a High Rip Current
Risk is already in effect for the northern beaches of PR. The
USVI beaches, along with Culebra, Vieques, and the western PR
beaches will likely be included in the High Rip Current Risk and
possible High Surf Advisory for Sunday, if not earlier for
Saturday afternoon.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Saturday afternoon for PRZ001-002-
     005-008.

     Heat Advisory until 5 PM AST this afternoon for PRZ001>005-007-
     008-010-011.

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

$$

SHORT TERM...DSR
LONG TERM....GRS
AVIATION...DSR
BEACH/MARINE...DSR