364
FXCA62 TJSJ 311719
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
119 PM AST Sun May 31 2026

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

.KEY MESSAGES...
Updated at 109 PM AST Sun May 31 2026

* Moderate concentrations of Saharan dust will continue to promote
  hazy skies and reduced visibilities through early next week,
  with higher concentrations this afternoon through Tuesday.
  Sensitive groups, including people with respiratory conditions,
  may experience discomfort and should follow medical
  recommendations.

* A tropical wave will continue to bring a brief surge in moisture
  content this afternoon, promoting an increase showers across
  the islands.

* Hot conditions are expected through early next week,
  particularly along the lower elevations and urban areas.

&&

.Short Term(This evening through Tuesday)...
Issued at 109 PM AST Sun May 31 2026

Conditions today were variable across Puerto Rico, particularly over
the eastern half of the island, where the day began mostly cloudy
with periods of passing showers. Rainfall accumulations generally
remained below 0.50 inches as the morning progressed. This cloud
cover was associated with a tropical wave moving across the region
gradually spreading westward, affecting the remainder of the island
through the late morning and early afternoon. Across the U.S. Virgin
Islands, skies remained partly cloudy with increasingly hazy
conditions. A gradual increase in Saharan dust concentrations was
also observed over Puerto Rico during the afternoon. Combined with
available low-level moisture and mid to upper level instability
associated with cooler temperatures and a trough aloft, these
conditions supported the development of lightning over Culebra and
over the Caribbean waters near Ponce.

Tonight, a dense Saharan Air Layer will continue to spread over the
northeastern Caribbean. While a few brief trade-wind showers may
move across windward sectors, rainfall activity is expected to
diminish as moisture levels gradually decrease. Model guidance
suggests precipitable water values near normals tonight before
falling to below-normal levels through Tuesday.

The dominant weather feature through Tuesday will be the extensive
Saharan dust plume becoming firmly established across the area. As
this dry air mass settles over the islands, atmospheric moisture
will steadily decrease, resulting in a more stable environment.
Meanwhile, 500 mb temperatures are forecast to persist between -8
degrees Celsius and -10 degrees Celsius, maintaining relatively cool
conditions aloft. Consequently, shower activity will become
increasingly limited by Monday, with only isolated and brief trade-
wind showers expected, mainly during the overnight and early morning
hours. Rainfall accumulations should remain minimal across Puerto
Rico and the U.S. Virgin Islands through Tuesday. The most
noticeable impacts will be reduced visibility, deteriorated air
quality, and warm to hot temperatures under generally sunny skies as
dust concentrations peak across the local area.

&&

.Long Term(Wednesday through next Saturday)...
Issued at 334 AM AST Sun May 31 2026

The long-term forecast remains on track with the arrival of a weak
easterly disturbance and an accompanying surge of moisture. This
will push precipitable water (PWAT) values up to a seasonal 1.50 to
1.75 inches. This setup will support a typical seasonal weather
pattern, bringing passing showers to eastern Puerto Rico and the
U.S. Virgin Islands during the morning hours, followed by afternoon
convective activity across central and western Puerto Rico. However,
despite the available moisture and low-level forcing, 500 mb
temperatures will remain slightly above normal for the season at
around -5C to -6C. This warmth aloft will limit instability and
vertical cloud growth, capping the overall development of widespread
thunderstorms.

At the mid-levels, a ridge will continue to promote drier air and
stable conditions aloft throughout much of the period, favoring
subsidence and limiting deep convection. By Thursday and Friday,
following the passage of the easterly disturbance, PWAT values are
anticipated to drop to near 1.00 inch, which is below normal for
this time of year. Consequently, rainfall should become very limited
and locally driven, with no impacts. This will result in a stretch
of mostly dry, fair weather and sunshine across both Puerto Rico and
the U.S. Virgin Islands.

By Saturday and into the weekend, the latest model guidance
continues to suggest a transition toward a more unsettled weather
pattern as a tropical wave approaches and an upper-level trough
moves into close proximity. However, because this is at the end of
the forecast period, uncertainty remains relatively high regarding
the exact timing and amount of the rainfall.

Meanwhile, warm conditions are expected to persist throughout the
entire long-term forecast. Seasonal to slightly above-normal
temperatures will hold steady through the weekend, with maximum
temperatures expected to range from the mid to upper 80s degrees
Fahrenheit along coastal and urban areas, and from the upper 70s to
low 80s across the higher elevations.

&&

.AVIATION...
(18Z TAFS)
Issued at 109 PM AST Sun May 31 2026

VFR conditions across all terminals. However, brief MVFR conds over
TJBQ and TJPS after 31/18Z -TSRA/SHRA can develop over interior to
W-NW PR through around 31/22Z. Over windward sectors, occasional
limited VCSH are possible. HZ prevail during the next 24 to 48 hrs
due to saharan dust with reduced VIS (btw 6 to 8 SM) possible. ESE
winds at 10 to 16 kt, with higher gusts and sea breeze variations,
decreasing after 31/23z.

&&

.MARINE...
Issued at 109 PM AST Sun May 31 2026

No changes were introduced to the marine forecast. The tropical wave
continues to move across the Caribbean Basin, with isolated to
scattered showers and thunderstorms affecting regional waters. Small
craft should exercise caution as thunderstorms may bring gusty winds
and lightning that may result in hazardous conditions. As mentioned
in the previous discussion, the Azores high will continue to promote
moderate to fresh east-southeasterly winds this week, which may lead
to choppy seas across regional waters. A dense plume of Saharan Dust
will gradually filter this afternoon, resulting in hazy skies,
reduced visibility, and a deterioration of air quality throughout
the week.

&&

.BEACH FORECAST...
Issued at 109 PM AST Sun May 31 2026

The low risk of rip currents should continue for the rest of today
across the islands. However, beachgoers should take into account
that isolated, stronger rip currents may occur, particularly near
groins, jetties, reefs, and piers. As winds are expected to
gradually strengthen by tomorrow, Monday, the risk should increase
to moderate for most beaches across the islands and persist for the
rest of the week. Beachgoers must exercise caution, as life-
threatening rip currents are possible along the surf zone.

In addition to rip currents, beachgoers are encouraged to remain
weather alert as showers and thunderstorms associated with a
tropical wave near the area may move near coastal areas of the
islands this afternoon. Moderate to high concentrations of Saharan
Dust will gradually filter into the region and persist throughout
the week, peaking this afternoon through Tuesday. These
concentrations may result in hazy skies, reduced visibility, and
poor air quality.

&&

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

$$

SHORT TERM/AVIATION...MMC
LONG TERM...GRS
MARINE/BEACH FORECAST...MNG