440
FXCA62 TJSJ 262049
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
449 PM AST Fri Jul 26 2024

.SYNOPSIS...

Very high concentrations of Saharan Dust will continue to move
over the local islands persisting through early Sunday. Hazy skies
will promote reduced visibilities and limited shower activity
throughout the weekend. An increase in shower activity is expected
by midweek as a strong tropical wave approaches the region.

&&

.SHORT TERM...Tonight through Sunday...

Calm weather conditions persisted today across the area. The
presence of a very dense Saharan Air Layer helped to inhibit
shower formation in the islands. Therefore, no rainfall activity
was observed today. Today, highs were seen in the low to mid 90s
along the coastal and urban areas, especially over the
northwestern and western coastal municipalities of Puerto Rico and
Saint Croix. In the other hand, temperatures remained in the 80s
in the higher elevations. Winds prevailed from the east at 10 to
20 mph with higher gusts.

A surface high pressure located in the central Atlantic will
continue to dominate the local weather conditions for the next
several days. The drier airmass over the region will persist
until midweek promoting mainly fair weather conditions and limited
shower activity. Nonetheless, by Sunday the latest model guidance
suggest the arrival of patches of moisture across the islands.
Passing showers will move over portions of eastern Puerto Rico and
the U.S. Virgin Islands during the morning hours, followed by
afternoon activity in the western side of Puerto Rico. A seasonal
pattern will return by the beginning of the workweek with warm to
hot temperatures.

.LONG TERM...Monday through Friday...

PREV DISCUSSION... /issued 449 AM AST Fri Jul 26 2024/

TUTT induced perturbations in the trades will reach the islands
from the east on Monday and early Tuesday morning. This will
promote seasonal weather conditions across the islands, with
passing trade wind shower across the USVI and eastern sections of
PR during the night and early morning hours, and afternoon
thunderstorm development over the interior and western PR.
Increasing the risk for urban and small stream flooding. Later on
Tuesday, a weak SAL moves in and hazy skies and limited shower
activity should prevail.

For Wednesday and Thursday, guidance still suggest an increase in
moisture content and breezy trades between 20-25 knots as a
tropical wave streams across the northeastern Caribbean. The
precipitable water content increases between 2.00-2.25 inches
during this period. The risk for urban and small stream flooding
will increase in general across the islands. Lingering moisture on
Friday will enhance the diurnal convection, and at the same time
another Saharan Air Layer is forecast to reach the eastern
Caribbean.

&&

.AVIATION...

(18Z TAFs)

Dense Saharan Air Layer will maintain hazy skies and reduced
visibilities around 6SM across the local flying area through the
forecast period. East winds at 15-20 kts, with stronger gusts and
sea breeze variations will continue, diminishing to 5-10 knots
after 26/23Z.

&&

.MARINE...

Surface high-pressure located in the central Atlantic will continue
to support moderate to fresh easterly winds and choppy seas for small
crafts over the next few days. A strong Saharan dust event will
continue to affect the local islands at least until early Sunday,
resulting in hazy skies and limiting shower activity. Increased
shower with thunderstorm activity is likely from Sunday onward.

&&

.BEACH FORECAST...

Increasing winds will promote a moderate risk of rip currents
across most beaches of St. Croix, and the east and southern coasts
of Puerto Rico.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning until 5 PM AST this afternoon for
     PRZ001>003-005-007-008-010>013.

VI...Excessive Heat Warning until 5 PM AST this afternoon for VIZ001-
     002.

AM...None.
&&

$$

SHORT TERM...LIS
LONG TERM....GRS
AVIATION...CAM
PUBLIC DESK...MRR