658
FXCA62 TJSJ 190627
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
227 AM AST Wed Aug 19 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 209 AM AST Wed Aug 19 2026

- A tropical wave (former Invest 94L) moving across the region,
  will bring periods of shower and isolated thunderstorms today.

- There is an elevated flooding risk across portions of central,
  western and northwestern Puerto Rico, particularly during the
  afternoon hours.

- A drier airmass will accompanied by low-to-moderate
  concentrations of Saharan dust will return tonight after the
  wave passage, persisting through the end of the week.

- There is a low risk of rip currents today across all beaches of
  Puerto Rico and the U.S. Virgin Islands.

&&

.Short Term(Today through Friday)...
Issued at 209 AM AST Wed Aug 19 2026

A tropical wave (former Invest 94L), currently with its axis located
over Puerto Rico, will continue to move westward across the region
overnight and into the morning hours. An increase in shower activity
is already visible on Doppler radar and satellite imagery, with
isolated to scattered showers primarily affecting eastern and
northern Puerto Rico, as well as the surrounding regional waters. No
significant rainfall accumulations have been reported so far.

As the wave moves farther west, abundant tropical moisture will
continue to filter into the region, increasing precipitable water
(PWAT) values up to 2.25 inches. This wave is interacting with an
upper-level trough to the northeast, increasing atmospheric
instability aloft. This instability will be further supported by
cooler mid-level temperatures (-7C at 500 mb), elevating the
potential for thunderstorms across the area. Current weather
patterns and the latest model guidance favor periods of moderate to
heavy showers and isolated thunderstorms across eastern Puerto Rico
and portions of the U.S. Virgin Islands during the morning. As the
day progresses, this activity will shift toward central, western,
and northwestern Puerto Rico during the afternoon. Additional shower
and isolated thunderstorm development is expected across the San
Juan metropolitan area due to streamer activity forming downwind of
El Yunque. Consequently, there is an elevated flooding risk across
western and northwestern Puerto Rico, alongside a limited risk
across the eastern interior and southeastern portions of Puerto Rico
and the U.S. Virgin Islands.

The moisture field from this tropical wave is expected to exit the
area by this evening into Thursday, replaced by a drier airmass
accompanied by low-to-moderate concentrations of Saharan dust. PWAT
values will drop rapidly to well-below-normal levels around 1.25
inches, persisting through at least Friday. Meanwhile, a surface
high-pressure system over the central Atlantic will maintain breezy
east-southeastern winds through the end of the week.

Cloud cover and rainfall associated with the tropical wave may bring
temporary relief from the recent warm spell. However, high
temperatures and heat indices exceeding 100F remain possible across
coastal and urban areas during the morning, depending on the extent
of cloud cover. Once the wave passes, an elevated to significant
heat risk is projected to return on Thursday and continue through
the rest of the week. Residents and visitors are encouraged to
monitor updating weather reports, take precautions against the heat,
and stay hydrated.

&&

.Long Term(Saturday through Wednesday)...
Issued at 209 AM AST Wed Aug 19 2026

A generally dry and breezy pattern is expected through the long-term
period. Very dry mid-level conditions, warmer-than-normal
temperatures aloft, and intermittent Saharan dust should limit the
depth and coverage of convection, although patches of low-level
moisture and a tropical wave crossing early next week may still
support brief passing showers and localized afternoon development.
No significant rainfall hazards are anticipated at this time.

Heat will remain the primary hazard, with elevated to locally
significant heat risk possible where sufficient sunshine occurs.
Persistent breezy winds, dry conditions, and limited wetting
rainfall may also continue to support elevated fire weather
concerns, particularly across the driest areas. Overall, hazards
should remain focused on heat and fire weather rather than rainfall
through the period.

&&

.AVIATION...
(06Z TAFS)
Issued at 209 AM AST Wed Aug 19 2026

Mainly VFR conds expected across all TAF sites through the
forecast period. A tropical wave will move across the region
today, resulting in periods of SHRA/TSRA. SHRA/VCSH expected to
increase this morning at TJSJ/TIST/TISX aft 19/06Z. Aftn SHRA/TSRA,
will result in VCTS at TJPS/TJBQ/TJSJ thru 19/22-23Z. This
activity could result in brief MVFR/IFR conds. Light winds at 10 kt
or less through 19/13Z. Winds E-ESE at 10-15 kt with sea breeze
variations and ocnl gusts up to 25 kt through 19/23Z.

&&

.MARINE...
Issued at 209 AM AST Wed Aug 19 2026

Light to moderate easterly trade winds will continue to
prevail across the region over the next few days. Seas are expected
to remain below small craft advisory criteria through the end of the
week. Today, a weak tropical wave will continue to bring showers and
thunderstorms across portions of the regional waters. This will
elevate localized lightning hazards and bring gusty winds. From
Thursday onward, expect hazy skies across the northeastern Caribbean
due to moderate concentrations of Saharan dust.

&&

.BEACH FORECAST...
Issued at 209 AM AST Wed Aug 19 2026

There is a low risk of rip currents today across all
beaches of Puerto Rico and the U.S. Virgin Islands. However, the
lightning potential will increase due to thunderstorm activity
associated with the arrival of a tropical wave. Through the rest of
the week, a low to moderate risk of rip currents is expected to
prevail across all islands as winds and seas ease across most
coastal waters. However, remember that even when the risk is low,
life-threatening rip currents can occur near groins, jetties, reefs,
and piers. Moderate concentrations of Saharan dust will promote hazy
skies on Thursday and Friday.

&&

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

$$

SHORT TERM...GRS
LONG TERM...ICP
MARINE/BEACH FORECAST...DSR