235
FXCA62 TJSJ 260901
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
501 AM AST Wed Mar 26 2025

.KEY MESSAGES...

* Breezy and gusty conditions will continue to create choppy to
  hazardous seas for small craft today, while also heightening
  wind and fire danger risks along coastal areas.

* Life-threatening rip currents are possible across most local
  beaches today.

* Wetter conditions with an increased flooding risk, as well as
  strengthening winds bringing hazardous seas and life-
  threatening surf zone conditions, are expected later this week,
  with conditions persisting into the weekend.


&&

.SHORT TERM...Today through Friday...

Current satellite derived precipitable water (PWAT) values indicate
patches of moisture near and over most of the region with values up
to around 1.40 over land. Satellite derived winds continue to report
speeds of around 15 to 25 mph over our surrounding waters. Scattered
showers under east-southeast steering flow reached the islands
during the overnight hours, including St. Croix, Vieques, Culebra,
most of the eastern third of PR, including the metropolitan area,
and some sectors of south-central to southeast PR. Low temperatures
were in the low to mid 70s at lower elevations of the islands and in
the upper 50s to mid 60s at higher elevations of Puerto Rico.

A surface high pressure over the northeastern Atlantic is tightening
the local pressure gradient, which will promote breezy to windy
trades today. A low pressure over the northeastern Atlantic and a
another surface high pressure over the eastern Atlantic will push
into the surface high currently over the northeastern Atlantic. As
the new surface high gradually builds during the second half of the
workweek, the steering flow will relax somewhat as it backs from
east to east-southeasterly (today and tomorrow) to easterly on
Friday and east to east-northeasterly Friday night and into the
weekend (also increasing on Friday).

A mid to upper level high will also persist through early Thursday,
promoting more stable conditions aloft and keeping available
moisture below 700mb. Breezy to windy trades will continue to bring
patches of moisture to the local islands. The diurnal pattern of
overnight and morning fast moving trade wind showers over windward
sectors of the islands will also include afternoon showers mainly
over west to west-northwest Puerto Rico today and Thursday, due to
diurnal heating, sea breeze convergence and local effects. Patches
of moisture with PWAT values at 1.5 to 1.7 inches will continue to
reach the region from the southeast today. By late tomorrow, a
frontal boundary as well as a mid to upper level trough will
approach the area, increasing moisture and instability. Available
moisture will reach above 500 mb by Thursday night, this will
promote vertical shower development. This will give way to a wetter
pattern to end the workweek and into the weekend (long term period).
This will strengthen the diurnal pattern, particularly on Friday, of
advective showers and afternoon convective showers, although with
the shift in steering flow, will concentrate more over the interior
to western-southwestern PR. Localized flooding is more likely on
Friday, particularly for windward areas of northeast PR at night and
over the interior to western-southwestern PR during the day. 925mb
temperatures will be at normal to above normal values for this time
of the year during the rest of the workweek (except on Friday when
more normal values are forecast).


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

The most recent global model guidance now suggests a wetter
pattern through most of the period. Combined with a persistent jet
aloft, this wet pattern will result from the remnants of a
frontal boundary during the weekend and pulses of moisture
driven by a low-level through to the southeast early next week.
These elements will sustain a dynamically favorable environment
for convective development. Strengthening east-to- east- northeast
winds will add to this scenario, producing breezy conditions
while also enhancing trade wind showers, particularly at night.

Reflecting the synoptic pattern, deep-layer moisture will peak
Saturday, with precipitable water (PWAT) values around 1.8
inches. Lower PWAT values will follow between Sunday morning and
Monday morning, before another gradual increase begins Monday
night. Rain chances will be highest during the weekend (50-70
percent), tapering to 40-50 percent on Monday, and back to 50-60
percent by Tuesday.

Localized flooding remains a concern, particularly for windward
areas of E-NE PR at night and interior to W PR by day during
periods of peal moisture. As rain chances decline on Monday, the
flooding risk will diminish, though isolated minor flooding
remains possible. Temperatures should remain near to slightly
warmer than climatological averages with no significant concerns.
Given recent model variability, any shifts in moisture
availability or wind flow could modify these impacts.


&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions prevailing at the TAF sites. Trade wind
-RA/SHRA can continue to reach TJSJ/TIST/TJPS/TISX at times. VCSH at
TJBQ btw 17-22Z. Mainly easterly winds up to around 20 kts with
higher gusts will prevail through 22Z, decreasing somewhat after.


&&

.MARINE...

A robust surface high pressure system over the Central Atlantic will
produce moderate to fresh trade winds through tonight. These
strengthening winds will generate choppy and rough seas, prompting
Small Craft Advisories for offshore waters and local passages through
late tonight. Hazardous conditions for small craft will likely return
by Friday into the weekend. Furthermore, a cold front and pre-
frontal trough approaching the region will increase shower and
thunderstorm activity starting Thursday.


&&

.BEACH FORECAST...

Breezy trades will continue today, promoting a moderate risk of
rip currents for most local beaches. Since life-threatening rip
currents are possible in the surf zone, beachgoers should exercise
caution. Deteriorating surf zone conditions will likely require a
high risk of rip currents over weekend, particularly for north-
and east- facing beaches. For more details, please refer to the
latest Surf Zone Forecast (SRFSJU).


&&

.FIRE WEATHER...

There is an elevated fire danger hazard risk today, particularly
for the southwestern coastal plains of Puerto Rico. While there
is a 20-30 percent probability of precipitation early this
morning for the area, today`s conditions will feature below-normal
moisture, significantly low relative humidity, breezy winds, and
gusty conditions. These factors elevate the risk for fast-moving
fires, particularly in grass-dominated areas. As a result, a Fire
Danger Statement (RFD) has been issued for these areas. Refer to
RFDSJU for details.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 AM AST Thursday for AMZ711.

     Small Craft Advisory until 6 PM AST this evening for AMZ723-733-
     741.

&&

$$

SHORT TERM...MRR
LONG TERM....ICP
AVIATION...MRR