973
FXCA62 TJSJ 140901
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Mon Jul 14 2025

.KEY MESSAGES...

* Hot temperatures and high humidity content this week will
  likely cause Heat Advisory conditions across the lower
  elevations and urban areas of Puerto Rico.

* Two tropical waves will increase shower and thunderstorm
  activity on Tuesday and Wednesday.

* A Saharan Air Layer with moderate to high concentrations of
  Saharan dust will cause hazy skies and poor air quality
  conditions from Thursday into the weekend.

* A moderate risk of rip currents returns across the east and
  northern beaches of the islands from midweek onward.

&&

.SHORT TERM...Today through Wednesday...

Scattered showers were observed overnight moving over the local
Atlantic and Caribbean waters and passages. Although, some of these
showers moved inland over eastern Puerto Rico and the U.S. Virgin
Islands, leaving minimal accumulations. Minimum temperatures were
from the mid 70s to low 80s along the coastal and urban areas to the
upper 60s to low 70s across the mountains. Winds were light from the
east-northeast with land-breeze variations.

A mid to upper level high pressure will continue to displace the
TUTT-low westward into the Hispaniola and Cuba, bringing stable
condtions aloft across the northeastern Caribbean. At the surface,
trade wind perturbations will move into the islands today into
Tuesday, promoting an increase in showers over the windward portions
of the islands during the morning hours. Later in the day, the
combination of daytime heating, local orographic effects and the
available moisture will promote the development of showers and
thunderstorms. In particular, across the Central Mountain Range into
the western municipalities of Puerto Rico, as well downwind from el
Yunque into the San Juan metro area and adjacent municipalities.

A tropical wave is expected to reach the islands by Wednesday,
increasing the moisture content across the region. The latest
precipitable water content (PWAT) guidance suggest values between
1.9 to 2.30 inches during the period. Therefore, increasing the
potential to observe showers and thunderstorms across all islands
through Thursday. At this time, there is a limited to elevated risk
to observe ponding of water in roads and poorly drainage areas, as
well as localized flooding in urban areas, roads and small streams.

Warm to hot temperatures will remain the first half of the 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 be above the 100 degrees Fahrenheit each day as well,
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.

.LONG TERM...Thursday through Monday...

On Thursday, southeasterly winds and an area of high moisture
content trailing a departing tropical wave will aid in the
development of early morning showers between the USVI and eastern
PR, followed by afternoon thunderstorms over west/northwest PR.
At the same time, a Saharan Air Layer (SAL) with moderate to high
concentrations of Saharan dust is expected to gradually fill
across the region. This will promote hazy skies, reduced
visibility, and poor air quality conditions through at least
Friday. The higher humidity content at the surface and the
southeast component in the winds will cause higher than normal
heat indices across most coastal and urban areas of the islands,
but particularly across the north and west coast of PR. Latest
guidance suggest Heat Advisory to Extreme Heat Warning conditions
before the onset of afternoon convection, and in cloud/rain-free
areas.

Also, warmer minimum temperatures at night due to the SAL preventing
efficient cooling at the surface will cause that days begin
warmer than normal. Therefore, hot temperatures are expected to
continue through at least Saturday and mainly across most coastal
and urban areas of PR. Heat advisory conditions will likely
continue each day. Residents and visitors, are advised to take
appropriate precautions during this period, particularly those who
are sensitive to heat and poor air quality conditions.

A TUTT-low and an induced low-level trough are expected to move
across the northeastern Caribbean early in the weekend. This will
bring an increase in shower activity again across the islands.
Another tropical wave is expected to move on Monday.


&&

.AVIATION...

(06Z TAFS)

VFR conds will prevail across all terminals thru the next 24 hrs.
However, afternoon SHRA/TSRA will develop across the western
interior affecting mainly TJBQ aft 14/17Z. Brief MVFR conds possible
btw 14/17-23Z. East winds expected btw 10-15 kt with sea breeze
variations and higher gusts aft 14/13Z.


&&

.MARINE...

A surface high pressure will strengthen over the western Atlantic
early this week. Two tropical waves will move across the eastern
Caribbean on Tuesday and Wednesday. Therefore, moderate to locally
fresh trades and choppy seas are expected across the regional waters
by midweek. Increasing shower and thunderstorm activity is expected
from Tuesday through Thursday. Hazy conditions due to Saharan dust
will return from Thursday onward.


&&

.BEACH FORECAST...

Rip current risk remains low across local beaches, but life-
threatening rip currents can still form near structures like groins,
jetties, reefs, and piers. Always swim near a lifeguard and follow
local beach safety guidance.

By late Tuesday, a moderate risk of rip currents will return along
the north and east facing beaches of Puerto Rico, Culebra,
Vieques, and St. Croix, driven by increasing winds.

Hot and humid conditions will continue throughout the week. Stay
hydrated, take breaks in the shade, and limit outdoor activity
during peak heat hours.


&&

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

$$

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