003
FXCA62 TJSJ 280922
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
522 AM AST Sat Jun 28 2025

.KEY MESSAGES...

* A seasonal weather pattern will persist today, with a limited
 excessive heat risk, especially in urban coastal locations.

* A tropical wave will approach Puerto Rico and the US Virgin
  Islands from the eastern Caribbean later tonight into Sunday,
  potentially promoting the formation of showers and thunderstorms
  across Puerto Rico and the US Virgin Islands.

* An area with slightly drier air and suspended Saharan dust
  particles will follow Sunday`s tropical wave, creating hazy
  skies and deteriorating air quality.

* Winds and choppy seas will continue to promote life-
  threatening rip currents across exposed beaches.

&&

.SHORT TERM...Today through Monday...

Today through Monday...

Variable to locally showery conditions persisted over several
northern coastal areas as quick passing showers under east-northeast
steering flow affected those areas. Accumulations were generally low
since midnight, with only very localized areas reaching up to a
quarter to half an inch. Stronger shower activity remained over the
waters; isolated t-storm activity was seen over the Mona Passage
during the overnight hours. Lows ranged from the upper 70s to low
80s at lower elevations and from the 60s to low 70s at higher
elevations.

Winds are veering, with recent radar scans indicating showers now
being steered by more easterly flow, steering flow will continue
to veer to become east-southeasterly today. These will continue to
steer moisture into the islands today with precipitable water
(PWAT) values from 1.60 to 1.90 inches, locally up to 2.00 inches
over northwestern PR. Passing showers under breezy winds will
continue to start the day, while stronger afternoon convection
will concentrate over interior to west-northwest PR with lines of
showers possible downwind of El Yunque and the local islands.

An upper level low will remain well northwest of the local area,
as it continues to be displaced by a mid to upper level ridge that
will continue to dominate during the rest of the short term
period. A Saharan Air Layer (SAL) is also approaching the area,
with moderate concentrations reaching the islands by tomorrow
morning and persisting through the rest of the short term period.
This Saharan Dust can result in hazy skies and deteriorated air
quality. However, a wind surge and a tropical wave (with its axis
just east of 60W) will also reach the area by tomorrow, Sunday,
deteriorating weather conditions. This wave will also bring a
surge in tropical moisture, increasing PWAT values to above 2
inches over the islands, promoting more widespread showers over
the islands, especially during the afternoon over interior to W-NW
PR and downwind of the local islands and El Yunque.

An increased flooding risk will remain on Sunday. Drier air will
quickly move in late Sunday night and into Monday, maintaining
available moisture below 850mb. This plus the above mentioned mid
to upper level ridge and persisting SAL will promote a drier start
to the workweek. A limited variant of the diurnal pattern with
hazy skies and breezy to windy conditions will be present on
Monday. At to above normal temperatures will persist during the
period, with a limited to possibly elevated heat risk.

.LONG TERM...Tuesday through Saturday...

A seasonal weather pattern will influence the meteorological
conditions, featuring a mix of clouds and sunshine, as well as
clear skies from Tuesday to Thursday. On Tuesday, we can expect
lingering suspended dust particles due to a mid-level ridge.
Additionally, easterly trade wind disturbances, caused by a trough
located in the mid-to-upper levels off the northeast of the
Lesser Antilles, will introduce occasional increases in shallow
moisture across the region. These surges of moisture may lead to
brief showers, particularly in windward areas, followed by
afternoon convection in western locations. However, this activity
is expected to be limited in intensity due to the trade wind cap
and subsidence aloft associated with the persistent mid-level
ridge, which is anticipated to remain in place through at least
Wednesday.

Temperatures are expected to be above normal, particularly due to
the SAL, which will hinder overnight cooling and result in warmer
minimum and maximum temperatures throughout the islands during
the first half of next week.

Conditions are expected to change late Thursday into Friday due to
the approach of a retrograding mid- to upper-level trough/low and
a tropical wave. This situation may lead to increased shower and
thunderstorm activity in the US Virgin Islands and Puerto Rico.
Conditions should rapidly dry out after this wave by late Friday
night into next Saturday, promoting the typical advective pattern
overnight and in the morning, followed by afternoon convection.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions will persist. Quick moving SHRA/-SHRA over
mainly TJBQ, TJSJ & TIST (with VCSH over TISX & TJPS) will persists.
Winds bcmg E-SE during the day up to 15 to 20 kts with sea breeze
variations and local effects after 28/13Z, decreasing at 28/23Z.
However, brief MVFR conditions are possible near TJBQ after 28/17Z
due to possible VCTS, lines of showers could also reach TJSJ at this
time.

&&

.MARINE...

Mariners can expect choppy seas across the local Atlantic and
Caribbean waters due to the surface high pressure across the
Atlantic, supporting a moderate to fresh easterly wind flow. A
tropical wave is expected to arrive by late Saturday night into
Sunday, increasing the potential for showers and thunderstorms across
the region. Another pulse with suspended Saharan Dust Particles will
follow the tropical wave from late Sunday night through at least
Tuesday.

&&

.BEACH FORECAST...

Wind-driven waves due to breezy easterlies will promote a
moderate risk of rip currents at some exposed beaches of the
islands today and for much of the forecast period.

&&

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

$$

SHORT TERM...MRR
LONG TERM....CAM
AVIATION...MRR