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170
FXCA62 TJSJ 160859
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Sat May 16 2026

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

.KEY MESSAGES...
Issued at 452 AM AST Sat May 16 2026

* Passing showers will continue to be steered by E to ESE winds
  towards E and S PR and the USVI to start the morning, followed by
  afternoon showers and possible isolated t-storms across interior
  to W-NW PR and downwind of El Yunque and the local islands.

* Above-normal temperatures will persist across the region this
  weekend, with heat indices reaching the upper 90s to low 100s
  during peak afternoon hours, especially across urban and coastal
  areas.

* An upper-level trough will approach the islands tomorrow, Sunday,
  onward. This can increase the frequency of showers and isolated
  thunderstorms.

* A moderate risk of rip currents will persist along many north and
  east facing beaches of Puerto Rico, Vieques, Culebra, and the
  USVI through much of the forecast period.

* Low concentrations of Saharan dust particles over the region will
  peak today and late tonight, gradually decreasing afterwards.

&&

.Short Term(Today through Monday)...
Issued at 452 AM AST Sat May 16 2026

Current satellite derived precipitable water (PWAT) indicate a patch
of moisture steered by east to east-southeast winds approaching the
region. PWAT values up to 1.74 inches (at normal values) are being
detected over the USVI due to this patch of moisture; values
gradually decrease westward down to 1.22 inches (below normal
values) over western PR. Showers have continued to be steered
towards windward areas with at least minimal accumulations detected
by radar since midnight over the USVI, Culebra and E to SE PR.
Patchy fog is also currently over sectors of interior PR. Lows have
been in the mid 70s to around 80 over urban and coastal sectors of
the islands, and in the upper 50s to the 60s at higher elevations of
PR.

East to east-southeast winds will continue to steer patches of
moisture towards the region during the period. PWAT values will be
generally at normal values as these patches of moisture move over
the region. However they can locally reach above normal values
during afternoon convection. Model guidance suggests more frequent
interruptions of drier air on Monday. Ridging that was present
during the past few days will continue to weaken today as an upper
trough approaches the area from the west and amplifies, increasing
instability during the period, especially tomorrow and Monday.
Showers will continue to be steered towards windward sectors,
prompting periods of variable to showery weather with moderate to
locally heavy rainfall at times. This can result in ponding of water
over roads and poorly drained areas with a chance of urban and small
stream flooding. Each afternoon, diurnal heating, local orographic
effects and sea breeze convergence will also aid in the development
of showers and possible isolated t-storms across interior to west
and northwest PR as well as downwind of El Yunque, and the USVI
towards eastern PR. As the upper trough continues to approach,
instability will also aid in the development of this afternoon
convection each day. This can result in a limited to elevated
flooding risk. Galvez-Davidson Indices are forecast at up to around
25 today, and at up to 35 to 40, tomorrow, Sunday. The presence of
some drier air in the mid-levels can help inhibit this activity.
Although rain is expected, the up to breezy east to east-southeast
flow will also promote above normal temperatures today and tomorrow,
as indicated by 925 mb temperature guidance. Highs will reach the
upper 80s to lower 90s across urban and coastal areas while heat
indices will exceed 100 to 105 degrees F during the afternoon
hours. This will result in a limited to elevated heat risk. Current
guidance suggests more high-end normal 925 mb temperatures on
Monday, prompting a limited heat risk. Low concentrations of
Saharan dust particles over the islands will peak today and late
tonight (prompting hazy skies at times), before gradually
decreasing tomorrow morning onwards.

&&

.Long Term(Tuesday through Saturday)...
Issued at 452 AM AST Sat May 16 2026

A gradual transition toward a wetter and somewhat more unstable
weather pattern is expected across Puerto Rico and the U.S. Virgin
Islands through the latter half of the upcoming workweek. Surface
high pressure over the western Atlantic will maintain moderate to
locally fresh easterly to east-southeasterly winds, with occasional
stronger and gusty periods. Early in the week, conditions should
remain relatively quiet overall, with intermittent patches of
moisture promoting passing showers across eastern Puerto Rico and
the U.S. Virgin Islands, followed by isolated afternoon convection
across western Puerto Rico. Rainfall coverage should generally
remain more dry than wet, especially across southern and eastern
Puerto Rico, which may continue to favor ongoing drought concerns.

At upper levels, a deep trough lingering over the western Atlantic
is forecast to gradually sink farther south late in the workweek,
supporting enhanced divergence aloft, cooling mid-level
temperatures, and a less dry environment across the region.
However, moisture continuity through the vertical column still
appears somewhat inconsistent, meaning moisture depth and
persistence will largely determine daily shower and thunderstorm
coverage. By late week, increasing moisture and stronger diurnal
heating should support more frequent afternoon showers and
thunderstorms across interior and western Puerto Rico, with flooding
concerns gradually increasing. Heat concerns will continue through
the period, although slightly cooler conditions may develop at times
due to increased cloud cover and rainfall activity.

&&

.AVIATION...
(06Z TAFS)
Issued at 452 AM AST Sat May 16 2026

Mainly VFR conditions at the terminals. -SHRA/VCSH will continue to
be steered by E to ESE winds and reach windward terminals from time
to time. Btwn 16/16-23Z SHRA/+SHRA will develop across interior to
NW PR, with isolated TS possible and lines of SHRA also developing
from the local islands and El Yunque. This can cause brief MVFR
conditions over TJBQ and TJSJ. E to ESE winds up to around 15 kts,
with higher gusts and sea breeze variations, decreasing after
16/23Z.

&&

.MARINE...
Issued at 452 AM AST Sat May 16 2026

A broad surface high pressure over the central Atlantic will promote
moderate to locally fresh east to east-southeasterly winds across
the regional waters through the weekend. Another surface high
pressure building over the western Atlantic will promote more
easterly winds early next week. These breezy conditions will
maintain somewhat choppy seas, particularly across the offshore and
exposed Atlantic and Caribbean waters. Seas are forecast to remain
between 4 and 6 feet during the next several days. Afternoon and
early evening isolated thunderstorms can be expected each day across
the western waters of Puerto Rico.

&&

.BEACH FORECAST...
Issued at 452 AM AST Sat May 16 2026

A moderate risk of life-threatening rip currents will prevail across
the east, north, and southern beaches of Puerto Rico and the U.S.
Virgin Islands through early next week. Beach goers should exercise
caution when entering these beaches. Life-threatening rip currents
often occur in the vicinity of groins, jetties, reefs, and piers.

If you become caught in a rip current, yell for help. Remain calm,
do not exhaust yourself and stay afloat while waiting for help. If
you have to swim out of a rip current, swim parallel to shore and
back toward the beach when possible. Do not attempt to swim directly
against a rip current as you will tire quickly.

&&

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

$$

SHORT TERM/AVIATION/KEY MESSAGES...MRR
LONG TERM....ICP
MARINE/BEACH FORECAST...DS

NWS SJU Office Area Forecast Discussion