703
FXCA62 TJSJ 090850
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
450 AM AST Thu Apr 9 2026

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

.KEY MESSAGES...
Updated at 450 AM AST Thu Apr 9 2026

* A High Risk of Rip Currents is in effect for the northern coast
  of Puerto Rico and Culebra today and possibly through the
  weekend due to pulses of northerly swells.

* Small craft should exercise caution over mainly the offshore and
  nearshore Atlantic Waters, and the Mona Passage, due to seas of
  5 to around 6 feet.

* Generally stable weather conditions are forecast, with isolated
  showers over windward areas and afternoon convection over mainly
  interior to W-NW PR through the rest of the week. An approaching
  trough will result in a wetter and more unstable pattern
  beginning early next week.

* For the U.S. Virgin Islands, generally fair weather conditions
  are expected through the rest of the week, with isolated
  showers from time to time.

* Normal to above-normal temperatures will persist through the
  rest of the week, prompting a limited heat risk.

&&

.Short Term(Today through Saturday)...
Issued at 450 AM AST Thu Apr 9 2026

Since midnight, radar estimated rainfall accumulations showed
minimal accumulations over interior, eastern and western sectors
of Puerto Rico, as light showers moved over those areas. Official
and unofficial stations have reported lows in the 70s across
coastal areas, with some reaching 78 to 80 degrees, and in the low
to upper 60s across interior PR. Patchy fog was also detected
over areas of the interior. Current satellite derived precipitable
water (PWAT) values indicate values at 1.65 to 1.80 inches (high
end normal to above normal values) over the islands with higher
values at around 1.90 over the northwestern and and southeastern
waters as moisture continues to be steered towards the islands. As
a broad surface high over the central Atlantic interacts with a
frontal low over the western Atlantic, winds will back during the
period to become more ESE to E. 925 wind speeds are forecast to
continue up to around 15 kts, normal for this time of the year,
however breezy continues are forecast at some lower elevation/coastal
areas. This flow will continue to steer broad moisture fields
towards the islands today and Saturday, and patches of both
moisture and drier air tomorrow, Friday. Vertical available
moisture will decrease as the period continues with 800 to 700 mb
relative humidities staying at normal values and 700 to 500 mb
relative humidities decreasing from above normal today to normal
tomorrow and Saturday. Although some instability at the area (in
part due to the frontal boundary and trough north of the area
along with some trade wind perturbations reaching the area),
subsidence aloft and warming 500 mb temperatures (mid level ridge)
will serve to limit shower development. Galvez- Davison Index
(GDI) values are forecast at up to 20 today and tomorrow and up to
30 on Saturday. Showers will continue to reach windward sectors
each morning and night, with afternoon convection due to diurnal
heating, sea breeze convection, and local effects forecast over
mainly interior to W-NW PR, as well as possibly downwind of the
local islands and El Yunque. Model guidance also suggests
afternoon convection over W-NW PR today, prompting a limited
flooding risk. Friday appears to be the day with least rain
activity. A limited flooding risk is also forecast for Saturday
due to afternoon convection over interior to W-NW PR. Patchy fog
over areas of the interior will continue during the overnight
hours. Low concentrations of Saharan Dust will persist over the
area through the rest of the week. 925 mb temperatures are
forecast to be near to above normal, with highs reaching the upper
80s to around 90 at urban and coastal areas. This pattern
suggests a limited heat risk is possible, particularly today and
tomorrow, Friday.

&&

.Long Term(Sunday through Thursday)...
Issued at 450 AM AST Thu Apr 9 2026

A transition toward a wetter and more unstable pattern is expected
beginning Sunday as a deep-layered trough approaches the region and
interacts with above-normal moisture. Early in the period,
conditions will still resemble a typical diurnal pattern, with
passing morning showers across eastern Puerto Rico and the U.S.
Virgin Islands followed by afternoon convection over western Puerto
Rico. However, as the trough moves closer and moisture increases,
shower and thunderstorm activity is expected to become more
widespread from late Sunday into early next week. The most active
period currently appears to be Monday into Tuesday, when deeper
moisture and cooler temperatures aloft will support more organized
convection. Thereafter, conditions should gradually trend toward
near-normal by mid to late week, although lingering moisture may
continue to support scattered shower activity. Confidence in this
overall pattern is moderate, particularly regarding the timing and
coverage of the wettest period.

The primary hazard will be an increasing risk of flooding,
especially from Monday into Tuesday when more persistent and
widespread showers and thunderstorms are expected. Periods of heavy
rainfall may result in ponding of water on roadways, urban and small
stream flooding, and isolated flash flooding where repeated activity
develops. Thunderstorms will also pose a risk of frequent lightning
and locally gusty winds. While impacts early in the period should
remain localized, the potential for more widespread and impactful
conditions increases early next week. Given the evolving pattern and
moderate forecast confidence, residents and visitors should continue
to monitor updates as details may change.

&&

.AVIATION...
(06Z TAFS)
Issued at 450 AM AST Thu Apr 9 2026

Mainly VFR conditions. Winds will gradually back to become more
ESE to E at up to 10 knots through 09/13z, increasing to 10 to 17
kts after, with higher gusts and sea breeze variations.
VCSH/-SHRA over the terminals. Around 09/17-22z SHRA/isolated TSRA
possible near or at JBQ. Winds decreasing to light and VRB after
09/23Z.

&&

.MARINE...
Issued at 450 AM AST Thu Apr 9 2026

Light to moderate east to southeasterly winds will prevail
throughout the day. Winds will turn more easterly from late tonight
and through the weekend as a broad surface high pressure builds from
the Central Atlantic. A small, but long period northeasterly swell
will linger across the Atlantic waters today. However, from late
tonight through Friday, a 4 to 5 feet northwest to north swell will
spread across the Atlantic waters and passages, building seas up to
6 feet. Therefore, small craft should continue to exercise caution.
Another pulse of the northerly swell is expected on Sunday. By early
next week, a frontal boundary and a pre-frontal trough will increase
showers and thunderstorms across the regional waters.

&&

.BEACH FORECAST...
Issued at 450 AM AST Thu Apr 9 2026

A series of small (2-4 ft), but long period northerly swells will
increase the threat of life-threatening rip currents along the
northern exposed beaches of the islands during the next few days.
Therefore, a High Rip Current Risk was issued for the northern
beaches of Puerto Rico and Culebra through at least late Friday
night. By early Sunday, another pulse from the northerly swell is
expected to reach local coastal waters of the islands, and the High
Rip Current Risk could be extended for the same areas through the
weekend. Across the USVI and Vieques, a moderate risk of rip
currents is expected to prevail through the same period.

&&

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

VI...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...MRR
LONG TERM....ICP
MARINE/BEACH...DSR

NWS SJU Office Area Forecast Discussion