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782
FXCA62 TJSJ 090539
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
139 AM AST Tue Jun 9 2026

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

.KEY MESSAGES...
Issued at 110 AM AST Tue Jun 9 2026

* Dangerous heat will continue through at least midweek. Heat
  indices will exceed 100F, especially across urban, coastal, and
  lower- elevation areas of Puerto Rico and the U.S. Virgin
  Islands. Therefore, a Heat Advisory is in effect through 5 pm
  today.


* An increase in moisture and instability is expected late
  Wednesday and Thursday, increasing the potential for showers and
  thunderstorms. The greatest impacts are expected across interior
  and western Puerto Rico during the afternoon and evening hours.

* Traces of Saharan dust will persist through the forecast period,
  producing somewhat hazy skies and reduced air quality,
  especially through tomorrow.

* Another increase in moisture is possible Sunday into Monday,
  supporting a return to a more active pattern of passing showers
  and afternoon thunderstorms across portions of Puerto Rico and
  the U.S. Virgin Islands.

&&

.Short Term(Today through Thursday)...
Issued at 110 AM AST Tue Jun 9 2026

Overnight, tranquil weather conditions prevailed across Puerto Rico
and the U.S. Virgin Islands under mostly clear skies and light,
variable winds. Temperatures remained in the upper 70s to low 80s
across coastal and urban areas, while mountainous locations cooled
into the 60s and low 70s.

Today through early Wednesday, the main concern will continue to be
the heat. Above-normal temperatures, limited rainfall activity,
and lingering Saharan dust will support hazardous heat conditions
across coastal, urban, and lower elevation areas. Model guidance
shows below-normal moisture levels, with precipitable water and
500 mb relative humidity values near or below the 25th percentile
for this time of year, while 925 mb temperatures remain above
normals. Consequently, dangerous heat indices are expected each
afternoon, prompting the issuance of a Heat Advisory to highlight
the elevated risk of heat-related illnesses, particularly for
vulnerable populations and those without adequate cooling or
hydration. Residents and visitors are urged to stay hydrated,
avoid prolonged outdoor exposure during peak heating hours, and
monitor sensitive individuals. Although overall conditions will
remain mostly dry, a few quick-moving showers may affect windward
areas during the morning, followed by isolated afternoon
convection across western Puerto Rico.

By late Wednesday into Thursday, conditions may become slightly
more unstable as a polar trough over the western Atlantic
amplifies and approaches the northeast Caribbean. This feature is
expected to enhance mid- and upper-level support across the
region, increasing the potential for afternoon showers and
thunderstorms, mainly across interior and western Puerto Rico.
While precipitable water values are forecast to remain near
seasonal levels, the added instability could still lead to more
active afternoon convection. At this time, the risk for
significant widespread flooding remains low. However, stronger
showers and thunderstorms may produce localized ponding of water
on roads as well as flooding in urban areas, small streams, and
washes. Residents and visitors should continue monitoring the
latest forecasts for updates as conditions evolve.

&&

.Long Term(Friday through Tuesday)...
Issued at 110 AM AST Tue Jun 9 2026

No major changes were made to the long-term forecast, as weather
conditions are expected to become drier and more stable over the
upcoming weekend and early next week. A surface high pressure
building over the Western Atlantic should increase the local
pressure gradient, leading to strengthening east-southeast winds and
resulting in breezy to locally windy conditions across the islands.
Friday has the highest potential for flooding and lightning, as
lingering moisture associated with a tropical wave and the proximity
of an upper-level trough should enhance afternoon convection. From
the latest model guidance, PWAT may vary between 1.7 and 1.9 inches,
which is typical for this time of the year, but shows abundant low
to mid-level moisture. Due to the proximity of the trough, mid-level
temperature should remain cooler than normal (500 mb temperatures
around -8 degrees Celsius), with enhanced vorticity, rising air, and
divergence aloft across the region, favorable for deep convection.
Additionally, the Galvez-Davison Index (GDI) suggests the potential
of isolated to scattered thunderstorms, particularly over the
western/northwestern side of the CWA in the afternoon. Although a
drier airmass will gradually filter into the region on Friday,
passing showers can still be expected during the morning hours over
windward sections of the islands, followed by afternoon convection
over interior and western/northwestern Puerto Rico. Additionally,
island streamers may develop and bring some showers into eastern
portions of Puerto Rico, including the San Juan Metropolitan area.
Rainfall accumulations could lead to ponding of water over roadways
and poorly drained areas, including minor flooding, over the
aforementioned areas. As the drier air mass continues to filter into
the region, patches of moisture may arrive throughout Saturday, with
shallow afternoon convection over western/northwestern Puerto Rico.
Sunday and Mondays forecast remains uncertain, as the latest global
model solutions show different outcomes for the CWA. The latest GFS
solution showed the upper-level trough lingering near the region,
with PWAT values remaining near above normal (up to 1.9 inches),
while the ECMWF solution suggests a mid-level ridge near the CWA,
with drier air in the 850 - 500 mb layer. Due to inconsistency with
the GFS solutions, Sunday and Mondays forecast was based on a
similar pattern to Saturday, with limited rainfall activity.

In terms of heat, warmer conditions may persist throughout the
forecast period as model guidance suggest typical to above normal
925 mb temperatures. With the available moisture, heat indices above
100 degrees Celsius cannot be ruled out, particularly across urban
and lower elevations of the islands. Hence, residents and visitors
should exercise caution as these levels could impact most
individuals, particularly those without adequate hydration and/or
effective cooling.

&&

.AVIATION...
(06Z TAFS)
Issued at 110 AM AST Tue Jun 9 2026

Mainly VFR conditions across all TAF sites. Expect the ESE winds
around 10-16 kt with higher gusts and sea breeze after 09/13Z.
VCSH possible across western Puerto Rico, affecting mainly TJPS
and TJBQ between 09/18Z and 09/23Z.

&&

.MARINE...
Issued at 110 AM AST Tue Jun 9 2026

The Azores high-pressure and a developing surface high in the
western Atlantic will produce moderate east to east-southeast winds
across regional waters, with occasional fresh winds causing choppy
conditions, especially offshore. A tropical wave is forecast to
reach the islands by Thursday, and This feature will likely increase
shower and thunderstorm activity, with the greatest potential from
Thursday afternoon to evening. Mariners should prepare for stronger
winds and higher seas near thunderstorms.

&&

.BEACH FORECAST...
Issued at 110 AM AST Tue Jun 9 2026

Generally, a low risk of rip currents will prevail today and
tomorrow, Wednesday, due to weakening winds. However, life-
threatening rip currents often occur in the vicinity of groins,
jetties, reefs, and piers. Please exercise caution on our local
beaches, as rip currents may still occur. A moderate risk of rip
currents (life-threatening rip currents are possible in the surf
zone) is forecast to return Thursday through the start of the next
workweek, especially along the east and north-facing beaches in PR
and the USVI.

&&

.FIRE WEATHER...
Issued at 110 AM AST Tue Jun 9 2026

Drier-than-normal conditions will enhance the availability of
burning fuels along the southern plains of PR and the USVI.
The fire danger fro today is low, as conditions are present.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for PRZ001>005-007-008-010>013.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
     for VIZ001-002.

AM...None.
&&

$$

SHORT TERM/AVIATION/FIRE WEATHER...MMC
LONG TERM...MNG
MARINE/BEACH FORECAST...MRR

NWS SJU Office Area Forecast Discussion