671
FXCA62 TJSJ 230655
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
255 AM AST Thu Apr 23 2026

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

.KEY MESSAGES...
Updated at 255 AM AST Thu Apr 23 2026

* Northerly swell pulses will bring a high risk of rip currents
  today, especially along north-facing beaches. Risk lowers to
  moderate thereafter.

* A limited flooding risk persists daily, becoming elevated this
  weekend into early next week. Isolated thunderstorms possible
  Saturday.

* Warmer-than-normal conditions develop this weekend, with heat
  indices near or above 100F.

* For the U.S. Virgin Islands, rip currents remain the main
  hazard, with a high risk today decreasing to moderate, while
  heat increases late in the period.

&&

.Short Term(Today through Saturday)...
Issued at 255 AM AST Thu Apr 23 2026

A relatively tranquil overnight period prevailed, with mostly
clear skies and little to no shower activity over land. This
pattern will persist into the morning hours as a drier air mass
remains in place, with below-normal precipitable water values
early in the day. Some moisture will gradually increase across
western Puerto Rico, while drier conditions linger over eastern
areas, Vieques, Culebra, and the U.S. Virgin Islands. Mid-level
dry air and a persistent inversion will limit vertical
development. Despite these somewhat hostile conditions, convection
is still expected, driven by daytime heating, with scattered to
locally numerous showers at times developing over the interior and
drifting toward nearby coastal areas during the afternoon.
Activity should remain brief and localized.

Moisture will continue to increase into the end of the workweek,
although it will remain mostly shallow in nature. Conditions will
stay fairly similar at first, and any convection that develops
will tend to drift north to northwestward on Friday with the
prevailing flow. By Saturday, a more southeasterly flow becomes
established, supporting warmer-than-normal conditions along with
stronger daytime heating. This evolving pattern will favor a more
active afternoon convection cycle, with showers developing over
the interior and shifting northward, with an isolated thunderstorm
possible.

The overall steering flow will remain weak through the period,
favoring slow-moving showers and localized flooding driven by
persistent rainfall over the same areas. This risk will remain
limited through Friday. By Saturday, increased moisture combined
with stronger heating and warmer-than-normal conditions will
support more efficient and heavier rainfall, leading to a slightly
elevated risk of excessive rainfall.

&&

.Long Term(Sunday through Thursday)...
Issued at 255 AM AST Thu Apr 23 2026

No significant changes have been introduced to the long-term period,
and the inherited forecast remains on track. A surface high-pressure
system over the central Atlantic will begin to migrate toward the
eastern Atlantic on Sunday, promoting a southerly wind flow through
Monday. Winds will veer from the south-southeast as the surface high
strengthens over the central-eastern Atlantic. By Sunday, a mid-
level ridge will bring drier, stable air, inhibiting the development
of strong showers and keeping precipitable water (PWAT) values near
1.25 inches(below seasonal averages).

An increase in moisture is anticipated from Monday into Tuesday,
with PWAT values rising to between 1.50 and 1.80 inches as a deeper
plume of moisture from the Caribbean arrives. The environment will
become increasingly unstable due to this moisture influx alongside
an upper-level trough, leading to more widespread shower and
thunderstorm activity across Puerto Rico and the U.S. Virgin
Islands. While passing showers are expected to move into the
islands, the most active rainfall is expected over the interior and
the western to northwestern portions of Puerto Rico during the
afternoon hours. Although 500 mb temperatures will remain within
seasonal values of -6 to -8C, isolated thunderstorms cannot be
ruled out each afternoon.

As this southerly flow prevails into next week, 925 mb temperatures
will increase to well above climatological values. Surface highs are
expected to range from the upper 80s to low 90s along coastal and
urban areas, and from the low to mid-80s across higher elevations.
Heat indices will climb as well, likely surpassing 100F from Sunday
into mid-week as the combination of southerly winds and abundant
moisture peaks during the daytime hours. To stay safe during this
period of high heat and humidity, residents and visitors are
strongly encouraged to prioritize hydration by drinking plenty of
water and avoiding prolonged exposure to the sun.

&&

.AVIATION...
(06Z TAFS)
Issued at 255 AM AST Thu Apr 23 2026

VFR conds will prevail at all TAF sites thru the fcst pd, with
brief MVFR possible at JPS btw 23/1622Z in VCSH. VCSH also
possible ovrngt at TISX. Winds will be lgt/vrb this mrng, bcmg ENE
812 kt with gusts up to 20 kt and sea breeze variations this
aftn, then returning to lgt/vrb ovrngt.

&&

.MARINE...
Issued at 255 AM AST Thu Apr 23 2026

A frontal boundary lingering just north of the region is
supporting light to gentle northeasterly winds, while pulses of a
long-period northerly swell continue to spread across the Atlantic
waters, resulting in hazardous seas for small craft, particularly
offshore. This swell will gradually subside late in the week. As
the boundary weakens, surface high pressure drifting southeastward
will promote a gradual strengthening of winds, becoming moderate
from the south over the weekend. Another northerly swell is
expected early next week. In addition, remnant moisture from the
frontal boundary may enhance shower activity over the waters, with
convection capable of producing locally hazardous conditions.

&&

.BEACH FORECAST...
Issued at 255 AM AST Thu Apr 23 2026

A high risk of rip currents is present along north to north-
northeast facing beaches of Puerto Rico, Culebra, and the northern
U.S. Virgin Islands as pulses of a long-period northerly swell
spread across the local waters, where life-threatening rip
currents are likely. Conditions will gradually improve, with the
risk decreasing by Friday, transitioning to moderate risk across
exposed areas, where rip currents remain possible, while low risk
persists along Caribbean-facing beaches. Another northerly swell
this weekend into early next week will bring a renewed increase in
rip current risk.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from 6 AM AST this morning through late
     tonight for PRZ001-002-005-008-010-012.

VI...High Rip Current Risk from 6 AM AST this morning through late
     tonight for VIZ001.

AM...Small Craft Advisory until midnight AST tonight for AMZ711-712.

&&

$$

MID...ICP
EVE...DSR/GRS

NWS SJU Office Area Forecast Discussion