National Weather Service Today's Weather Impact Levels

901
FXCA62 TJSJ 231813
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
213 PM AST Thu Apr 23 2026

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

.KEY MESSAGES...
Updated at 208 PM AST Thu Apr 23 2026

* Northerly swell pulses will maintain a high risk of rip currents
  through at least late tonight, especially along the USVI and
  PR`s north-facing beaches.

* Pulses of northeasterly swells will promote life-threatening
  rip currents along these beaches from the weekend into early
  next week. Afternoon convection will maintain a limited flooding
  risk each day across Puerto Rico, with the risk becoming
  elevated this weekend and into early next week.

* The region of PR and the USVI will move to a warmer-than-
  normal period from tomorrow afternoon onward, with heat indices
  near or above 100F.

&&

.Short Term(This evening through Saturday)...
Issued at 208 PM AST Thu Apr 23 2026

In general, the US Virgin Islands and Puerto Rico observed little
or no rain, with mostly clear skies this morning. However, by
noon, cloudiness began to increase across the interior of Puerto
Rico and the US Virgin Islands due to local effects. Showers
developed across the interior and southwest PR after noon. Maximum
temperatures ranged from the mid-80s to the low-90s at coastal
sites and from the upper-70s to mid-80s at mountain sites. The
winds calm to light and variable under the influence of sea breeze
variations.

This afternoon, showers will form later across the interior,
spreading to the mountain slopes, where a limited risk of flooding
rains remains. Across the U.S. Virgin Islands, generally calm
conditions are expected, with some showers downwind from the
islands. We cannot rule out showers tonight and overnight as the
front approaches from the north-northwest.

Model guidance shows instability increasing from late tonight
onward as a mid to upper-level trough approaches the region from
the west. The weak steering wind flow will maintain a limited risk
of flooding on Friday. Under the aforementioned weather pattern,
the chance of strong thunderstorms will increase, especially each
afternoon as it moves closer to the region. Some of the limiting
factors observed are the dry air at mid levels, which could
inhibit widespread activity, even though available moisture will
increase at low levels.

By Saturday, a more southeasterly flow will become established,
promoting warmer-than-normal temperatures and enhanced diurnal
heating. This pattern will support a more active afternoon
convection cycle, with showers developing across the interior and
drifting northward, with isolated thunderstorms possible. The
combination of increasing moisture and stronger heating will also
enhance rainfall efficiency, raising the potential for locally
heavy rainfall and a slightly elevated risk of excessive rainfall.


&&

.Long Term(Sunday through next Wednesday)...
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...
(18Z TAFS)
Issued at 208 PM AST Thu Apr 23 2026

VFR conds will persist across all TAF sites. Aft -SHRA/+SHRA will
move across interior PR, resulting in VCSH for JPS through 23/23z.
With light winds, -SHRA may move inside TAF site, AMDs will be issue
if required. Winds from the E-ENE will weaken and become VRB
after 23/23z, strengthening btwn 8 - 12 kt from the E-SE. VCSH may
reduce CIGs/VIS over IST and ISX by 24/12z.

&&

.MARINE...
Issued at 208 PM AST Thu Apr 23 2026

A frontal boundary will linger near or north of the region through
late Friday night. This system will promote calm to light flow
across the region. At the same time, a pulse of northerly swell
will create hazardous marine conditions through this evening. A
surface high pressure behind the front will then slowly build from
the western to central Atlantic, promoting east-southeast to
southerly winds from Saturday into early next week. Pulses of
northeasterly swell will arrive around Saturday and another one
around Sunday, which will dominate local seas.

&&

.BEACH FORECAST...
Issued at 208 PM AST Thu Apr 23 2026

Beachgoers, life-threatening rip currents are impacting the
north-facing beaches from Rincon to Fajardo, as well as the
northern beaches in Culebra, St. Thomas, St. John, and adjacent
islands. These conditions will last through at least late tonight.
Then, we expect the risk to turn moderate on Friday; however,
with the arrival of another northeasterly swell, the risk could
jump back to high for north- and east-facing beaches during the
weekend. We encourage active monitoring of beach conditions for
additional updates.

The risk of rip currents will be low in the south-facing beaches
of Puerto Rico and the U.S. Virgin Islands.

In addition, beachgoers should remain alert for afternoon
thunderstorms, particularly across western Puerto Rico. These
storms may produce gusty winds and frequent lightning.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for PRZ001-002-005-
     008-010-012.

VI...High Rip Current Risk through late tonight for VIZ001.

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

     Small Craft Advisory until 6 PM AST this evening for AMZ742.

&&

$$

MORNING CREW...CAM/MNG
EVENING CREW...DS/GRS

NWS SJU Office Area Forecast Discussion