262
FXCA62 TJSJ 081800
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
200 PM AST Tue Jul 8 2025

.KEY MESSAGES...

* Moderate to high concentrations of Saharan dust are expected to
  return during the second part of the workweek, resulting in hazy
  skies, reduced visibility, and poor air quality.

* Breezy conditions are expected through Wednesday. Choppy seas
  and a moderate risk of rip currents will persist over the next
  few days. These may create hazardous conditions across the
  Atlantic waters.

* Diurnally induced afternoon showers and isolated thunderstorms
  are expected over portions of the Cordillera Central and western
  PR each day. Passing showers will continue across the USVI and
  eastern sections of PR during the night/early morning hours.


&&

.SHORT TERM...Today through Thursday...

Sunny to partly cloudy skies were observed across the islands
today. Diurnally induced showers and isolated thunderstorms were
developing over the northwest quadrant of Puerto Rico early this
afternoon, and are expected to continue over the western waters of
PR thru this evening. Maximum temperatures were from the
upper-80s to the low 90s across the lower elevations of the
islands, and from the mid-70s to mid-80s across the higher
mountains of Puerto Rico. The wind was from the east to southeast
between 16 and 22 mph with sea breeze variations and higher gusts
between 32 and 37 mph observed across coastal areas of all the
islands.

A wind surge will bring scattered showers and stronger winds across
the area from tonight through Wednesday. Another tropical wave
with a band of moisture of 1.80 inches of precipitable water will
stream across the area on Thursday. However, higher
concentrations of Saharan dust mixed with the tropical wave could
hinder shower activity in general. Having said that, the overall
available moisture content is forecast to remain around normal
levels, fluctuating in general between 1.50-1.80 inches through at
least Thursday afternoon. Therefore, we expect a similar weather
pattern each day with passing showers across the USVI/eastern
half of PR during the night/early morning hours, followed by
diurnally induced afternoon showers and isolated thunderstorms
developing over portions of central and western PR, and streamers
developing downwind of the USVI and from el Yunque area. Most of
this activity across PR will cause ponding of water on roads and
poor drainage areas, and urban and small stream flooding where
thunderstorms develop.

At the lower levels, a broad ridge building from the central
Atlantic will promote east to southeast winds for the next few
days. The higher moisture content near the surface and these winds
will promote normal to above normal temperatures each day and a
limited heat risk will persist for the lower elevations and urban
areas of the islands. Higher concentrations of Saharan dust on
Thursday will promote hazy conditions and poor air quality.

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

/From Prev Discussion issued at 500 AM AST Tue Jul 8 2025/

The inherited forecast remains on track. The latest model guidance
continues to support a surface wind surge crossing the region on
Friday, leading to a brief increase in low-level moisture. This may
support isolated to scattered showers early in the day. However, a
significantly drier air mass is expected to filter in by late Friday
and continue through the upcoming workweek, suppressing widespread
convection. At the same time, mid- to upper-level dry air and a
reinforcing trade wind inversion will further limit vertical cloud
development. Additionally, the arrival of a Saharan Air Layer
will contribute to hazy skies, reduced visibility, and potential
impacts on air quality, especially for sensitive groups. This
dusty and dry environment will also act to suppress rainfall
through Saturday. Breezy to windy conditions will prevail both
Friday and Saturday, with easterly winds supporting above-normal
temperatures, particularly in coastal and urban areas.

By Sunday, the Tropical Upper-Tropospheric Trough (TUTT) is forecast
to shift westward toward Hispaniola. This transition, combined with
the approach of easterly trade wind disturbances, will begin to
increase atmospheric moisture over the region. As a result, rain
chances will rise on Sunday afternoon, with a more favorable
environment for convection.

Monday and Tuesday will likely feature the highest rainfall
potential as deeper tropical moisture becomes established across
Puerto Rico and the U.S. Virgin Islands. Scattered showers and
thunderstorms are expected each afternoon, especially in western and
interior sections. Although the threat of excessive rainfall
remains low until late Sunday into Monday, other weather concerns.

&&

.AVIATION...

(18z TAFs)

Mainly VFR conditions are expected across all terminals during
the next 24 hours. However, SHRA/TSRA expected to develop in and
around TJBQ thru 08/22z. Across the USVI terminals and TJSJ,
mostly VCSH expected with brief periods of -RA. The 08/12z TJSJ
sounding indicated ESE winds up to 27 kt blo FL120. HZ will
gradually increase during the next day or so, but VSBY should
remain P6SM. However, higher concentrations of Saharan dust return
from Thursday onward and visibilities could drop to 5-6 SM.


&&

.MARINE...

Moderate to fresh trade winds will create choppy seas across
local waters over the next several days, small craft should
exercise caution. Small Craft Advisories will possibly be issued
later on for Wednesday. Afternoon thunderstorms may impact coastal
waters and local passages, particularly over western Puerto Rico
and the Mona Passage each day. Showers and thunderstorm chances
increase on through Thursday with the passage of tropical waves.
Saharan dust is expected to return later in the workweek.


&&

.BEACH FORECAST...

Increasing winds over the next several days will promote a moderate
risk of rip currents across the eastern, northern, and southeastern
beaches of Puerto Rico, Vieques, Culebra, St. Thomas. and St. Croix.
Life-threatening rip currents often occur in the vicinity of groins,
jetties, reefs, and piers.


&&

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

$$

DSR/GRS