013
FXCA62 TJSJ 291846
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
246 PM AST Sun Jun 29 2025

.KEY MESSAGES...

* Hazy skies and poor air quality from moderate concentrations of
  Saharan dust will continue through Monday.

* Breezy conditions are expected through midweek. This will also
  cause choppy seas and a moderate risk of rip currents.

* Another tropical wave is forecast to affect the islands on
  Friday, again increasing shower and thunderstorm activity.


&&

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

Partly sunny to variably cloudy skies prevailed across Puerto
Rico and the U.S. Virgin Islands today. Moisture associated to a
tropical wave remained well south of the region, and limited
shower activity was observed in general across the islands. In
addition, a wind surge and a Saharan Air Layer brought mostly
breezy and hazy conditions. 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 between 15
and 20 mph with sea breeze variations and higher gusts across
coastal areas.

For the rest of this afternoon, diurnally induced showers and
isolated thunderstorms can still develop over the west coast of
Puerto Rico. Across the U.S. Virgin Islands and eastern PR, a
wind surge will continue to promote breezy conditions and shallow
cloudiness with limited shower activity. These breezy conditions
will prevail through most of the short term period as a low-to
mid-level ridge moves from the east and across the northeastern
Caribbean. Embedded in this flow, a Saharan Air Layer with drier
air and moderate concentrations of suspended Saharan dust will
continue to promote mainly fair weather conditions and hazy
conditions across the area. For Tuesday, passing showers and a
slight increase in moisture is expected as a weak trade wind
perturbation streams over the area. However, the precipitable
water content is forecast to remain below normal levels, between
1.25-1.50 inches.

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

/From Prev Discussion issued at 521 AM AST Sun Jun 29 2025/

Surges of moisture will result in increases in precipitable water
(PWAT) content on Wednesday as they are steered towards the islands,
but overall PWAT values will be very variable as surrounding drier
air is also present. Available moisture can reach up to around 700
mb, contrasting the more pronounced cap that will be present to
end the short term period. The diurnal shower pattern can still be
limited on Wednesday and for most of Thursday, with passing
morning showers and afternoon showers and isolated thunderstorms
over western PR, where a limited flooding risk will remain. By
Thursday through late Friday, a gradual increase in PWAT is
forecast, especially on Friday as values reach above 2 inches.
Current model guidance, has most if not all of the region with 2
inches or more of PWAT. Available moisture at this time will also
be present in the mid to upper levels. Late Thursday through
Friday is expected to be the wettest period, as a tropical wave
approaches the islands and a retrograding mid- to upper-level
trough is also nearby. This will promote a boost in the diurnal
pattern and overall increased shower and t-storm activity over the
region, a limited to elevated flooding risk will remain. PWAT
values will quickly drop to below normal by Saturday before
bouncing back to around 1.90 in by Sunday as moisture remains of
the wave are circled back towards the islands by the surface high.
This surface high over the Atlantic will also promote up to
breezy east to east-southeast steering flow during the period. 925
mb temperatures will be above normal with a limited to possibly
elevated heat risk each afternoon. The presence of saharan dust,
increasing as the period continues, can also serve to limit
nighttime cooling.


&&

.AVIATION...

(18Z TAFS)

Mainly VFR conditions expected across all terminals during the
next 24 hours. However, -TSRA/SHRA can develop in and around TJBQ
thru 29/22z, leading to brief MVFR conds. Moderate concentrations
of Saharan dust will result in HZ, with visibility occasionally
reduced to 6 SM.


&&

.MARINE...

Mariners can expect choppy seas up to 6 feet and east winds up to
20 knots across the local Atlantic and Caribbean waters due
persistent moderate to fresh easterly winds. Saharan dust will
promote hazy skies through at least Tuesday.


&&

.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/LIS