National Weather Service Today's Weather Impact Levels

306
FXCA62 TJSJ 221606
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1206 PM AST Fri May 22 2026

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

.KEY MESSAGES...
Issued at 1205 PM AST Fri May 22 2026

* At least through the Holiday weekend: morning passing showers
  are expected across the windward areas of Puerto Rico and the
  U.S. Virgin Islands, followed by afternoon thunderstorms across
  central and western Puerto Rico.

* A moderate risk of life-threatening rip currents will persist
  across all northern, eastern and southern beaches of the islands.

* Breezy conditions will result in choppy seas through early next
  week.

&&

.Short Term(This afternoon through Sunday)...
Issued at 1205 PM AST Fri May 22 2026

Current satellite-derived Total Precipitable Water (TPW) imagery
shows an expansive plume of moderate tropical moisture filtering
west-northwestward into the eastern Caribbean. According to the
latest GFS run, precipitable water values will fluctuate between
1.75 and 2.00 inches through Saturday, then increase to near 2.15
inches by Sunday. Mid-level and low-level relative humidity are
expected to spike well above the 75th percentile on Saturday,
peaking near 80-90% in the 700-500 mb layer. This setup will
interact with daytime heating, local effects, and brisk easterly
winds driven by a strong surface high pressure in the central
Atlantic, producing afternoon showers and thunderstorms each day.

Consequently, high-resolution NBM and ECMWF ensemble guidance
agree on a significantly wetter pattern developing over the
weekend. For today, expect a relatively standard diurnal
convective pattern with scattered showers and afternoon
thunderstorms over western/interior Puerto Rico with periods of
locally heavy rainfall, and across the USVI and eastern PR,
generally light to moderate localized accumulations (0.25 to 0.75
inches). However, as deeper moisture arrives on Saturday, shower
and thunderstorm coverage will increase substantially. By Sunday,
aided by the increasing PWAT values and deep-layer saturation,
widespread showers and isolated to scattered thunderstorms are
anticipated across the islands. Guidance suggests daily rainfall
accumulations of 1 to 2 inches, with localized maximums
potentially exceeding 3 inches along the eastern half and western
Puerto Rico. Given the expected saturated profile, increasing
rainfall rates, and consecutive days of precipitation, the threat
of urban, small stream, and localized flash flooding will be
elevated through Sunday afternoon.

&&

.Long Term(Monday through next Friday)...
Issued at 148 AM AST Fri May 22 2026

Variable conditions are still expected in the long-term forecast,
with Tuesday and Wednesday being the most unstable. A broad surface
high pressure over the western Atlantic is expected to extend into
the Central Atlantic, with winds shifting from the E-SE through most
of the period. Strengthening winds will bring breezy conditions
throughout the long-term forecast, with Monday the windiest day.
Although a mid-level ridge is expected to build over the Western
Atlantic, troughiness associated with an upper-level trough will
maintain slight instability across the CWA. The latest model
guidance solutions continue to suggest an increase in moisture
content in the region, with the latest solution showing PWAT values
near to above normal (between 1.8 and 2.0 inches, with a low chance
of reaching 2.2 inches). Additionally, low to mid-level moisture
should ascend to well above climatological normal (60 - 80%), with
model soundings suggesting skinny profiles. In terms of instability,
deep convection is expected across the region, particularly during
the afternoons and evenings, as mid-level temperatures should remain
cool (between -7 and -8 degrees Celsius), while guidance shows
signals of enhanced vorticity on Tuesday and Wednesday. These
conditions combined with local effect and daytime heating should
allow deeper convection activity. For each day, expect passing
showers moving over windward sections of the islands throughout
the day, with afternoon convection over interior and western to
northwestern Puerto Rico. Additionally, island streamers could
move over eastern Puerto Rico, including the San Juan Metro Area,
increasing flooding potential. Due to fast-moving showers,
rainfall accumulations should remain limited, resulting in ponding
of water across roadways and poorly drained areas and minor
flooding over the aforementioned areas. However, urban and small
stream over localized areas cannot be ruled out. In addition to
flooding, hazards such as gusty winds and lightning can be
expected during periods of heavy showers. Weather conditions
should gradually improve by the end of the period.

In terms of heat, model guidance continues to suggest temperatures
typical for this time of the year. However, combined with available
moisture, localized urban and coastal areas of the islands may
experience heat indices reaching 100 degrees Fahrenheit. Although
the risk will remain limited, individuals sensitive to heat should
take the necessary precautions.

&&

.AVIATION...
(12Z TAFS)
Issued at 1205 PM AST Fri May 22 2026

Mainly VFR conditions expected. However, SHRA/TSRA will develop
across the interior and NW PR, and downwind from El Yunque possibly
resulting in brief MVFR conds at TJBQ/TJSJ thru 21z. The 22/12z
TJSJ sounding indicated ESE winds up to 22 kt blo FL060. Sfc winds
will prevail from the east overnight at 8-12 kt. Passing SHRA en
route fm the Leeward terminals should cause mostly VCSH across the
USVI terminals.

&&

.MARINE...
Issued at 1205 PM AST Fri May 22 2026

Moderate to fresh easterly winds will continue across the regional
waters through next week due to a strong surface high pressure
over the central Atlantic. Choppy seas up to 6 feet will persist
across the offshore water and passages, and small craft should
exercise caution. Stronger winds and rough seas are expected by
Monday, and Small Craft Advisory conditions are possible across
the offshore Atlantic waters on Monday and Tuesday. Isolated
afternoon thunderstorms are expected to develop near the western
coastal waters of Puerto Rico, producing locally higher winds and
seas each day.

&&

.BEACH FORECAST...
Issued at 1205 PM AST Fri May 22 2026

A moderate risk of rip currents will persist across most local
beaches through the next several days due to persistent breezy
conditions and wind-driven seas. The highest risk will continue
along north, east, and south facing beaches of all the islands.
A moderate risk of rip currents means that life-threatening rip
currents are possible in the surf zone.


&&

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

$$

SHORT TERM...DSR
LONG TERM....MNG
AVIATION...DSR
MARINE/BEACH...DSR

NWS SJU Office Area Forecast Discussion