581
FXCA62 TJSJ 091833
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
233 PM AST Thu Oct 9 2025

.KEY MESSAGES...

* The shower and thunderstorm activity across Puerto Rico will
  remain through at least sunset. The moderate risk of urban and
  small stream flooding remains.

* Deep tropical moisture from Jerry will help support rounds of
  showers and thunderstorms through the weekend, maintaining a
  moderate risk of flooding, mostly for eastern Puerto Rico and
  the Virgin Islands.

* Dangerous marine conditions for small crafts and hazardous
  beach conditions are forecast as swells from Jerry reach the
  regional waters by late tonight and continue into Saturday.

* For the U.S. Virgin Islands, particularly St. Thomas and St.
  John, conditions could deteriorate furtheR after tonight.
  Periods of gusty winds, rough seas, and locally heavy rainfall
  are possible from Friday into the weekend.

&&

.SHORT TERM...Rest of Today through Sunday...

Localized showers and isolated thunderstorms have developed this
afternoon across portions of Puerto Rico, including the San Juan
metro area, with streamer activity noted downwind of the U.S. Virgin
Islands and nearby smaller islands. Weak steering flow today will
favor slow-moving showers and thunderstorms, increasing the risk of
localized flooding, particularly across urban, low-lying, and poor-
drainage areas. Any additional rainfall this afternoon will
contribute to soil saturation and rising streamflows, further
increasing flood risk ahead of Tropical Storm Jerrys approach to
the northeastern Caribbean.

By Friday, Jerry will pass to the northeast of Puerto Rico and the
U.S. Virgin Islands, with its closest approach expected late tonight
into early Friday morning. The storms outer circulation will
interact with a weakening surface trough located northwest of the
area, influencing low-level steering winds across the region through
the weekend.  Weak northerly steering winds will persist on Friday,
promoting slow-moving convection that may repeatedly develop over
the same areas. As a result, periods of heavy rainfall, frequent
lightning, and localized gusty winds are likely, particularly across
eastern, northern,

By Friday, Jerry will pass northeast of Puerto Rico and the U.S.
Virgin Islands, with its closest approach expected late tonight into
early Friday morning. Weak northerly steering winds will persist
through the day, promoting slow-moving convection capable of
producing heavy rainfall, frequent lightning, and localized gusty
winds. With soils already saturated from recent activity, the
potential for urban and small-stream flooding will remain elevated,
particularly across the eastern third of Puerto Rico and the Virgin
Islands. At the mid levels, a ridge positioned west-northwest of the
area will promote some dry air intrusion and vertical wind shear,
placing the region near the boundary between the drier air to the
west and the deeper tropical moisture field associated with Jerry.
This setup will create variability in rainfall intensity and
coverage, with areas under deeper moisture experiencing more
persistent convection. Any minor changes in Jerry`s track will
influence this setup.

On Saturday, as Jerry continues to move northward, low-level winds
will shift to a southerly flow, drawing abundant tropical moisture
across the region. This will sustain another active day of scattered
to numerous showers and thunderstorms, capable of producing
torrential rainfall and brief gusty winds. Flooding threats will
persist due to the saturated soils, while above-normal temperatures
and humidity will push heat indices near or above heat advisory
levels, especially in coastal and urban areas prior to afternoon
convection.

By Sunday, lingering tropical moisture combined with the continued
southerly flow will maintain warm, humid, and unstable conditions.
Afternoon convection is expected to redevelop over interior and
northwestern Puerto Rico due to sea breeze convergence. The
combination of high temperatures, saturated soils, and slow-moving
convection could prolong flooding and heat-related impacts through
the end of the weekend.

Residents and visitors are urged to remain alert to rapidly changing
weather conditions and continue monitoring official updates from the
National Hurricane Center and the National Weather Service in San
Juan as Tropical Storm Jerry passes northeast of the area.


.LONG TERM...Sunday through Thursday...
//from previous discussion//

The latest Advisory by the National Hurricane Center has Tropical
Storm Jerry, a hurricane by that time, about 740 miles north of
San Juan by Sunday. Moisture plume trailing Jerry will continue to
promote PWAT values generally at 2 to 2.3 inches, normal to above
normal values for this time of the year, through at least late
Monday, with deep moisture being present. On Monday above normal
moisture will gradually filter out to the west while drier air
filters in from the east. Steering flow will start southeasterly
on Sunday, gradually becoming more easterly on Monday. Patches of
below normal to above normal moisture will filter over the islands
Tuesday through Wednesday. Mid to upper level ridging will be
present for most of the period, however a deep level trough will
dig down towards the eastern Caribbean by Wednesday and Thursday.
Current model guidance has an increase in PWAT values once again
late Wednesday into Thursday as moisture from a frontal boundary
moves over the area bringing above 2 inches of PWAT to end the
forecast period. As a surface low moves towards the western
Atlantic and a high positions itself over the eastern Atlantic,
steering flow will become southeasterly on Tuesday, southerly to
southwesterly on Wednesday and southwesterly by Thursday. Flooding
risk remains, particularly during afternoon convection steered by
the dominant winds, due to diurnal heating, sea breeze
convergence and local effects, and due to the plumes of moisture
at the beginning and end of the forecast period. Southerly
component of the winds will also aid in sustaining a heat risk
during the period.

&&

.AVIATION...
(18Z TAFS)

Mainly VFR conds expected through the period, but MVFR/IFR posbl in
SHRA/TSRA this aftn mainly TJSJ, TJBQ, TJPS, ISX. Reduced VIS and
CIGS expected over or en route downwind of USVI TAF sites. Activity
diminishing aft 10/02Z. Mtn obscurations likely over interior PR
during peak convection. Light and variable winds expected thru the
period as TS Jerry moves NE of the area.

&&

.MARINE...

Tropical Storm Jerry is currently over the central Atlantic and
forecast to pass well northeast of the local islands by late tonight
into Friday. Although no direct tropical storm impacts are expected,
indirect marine impacts will spread across the regional waters by
late tonight night into the weekend. Swells generated by Jerry will
lead to hazardous seas up to 8 to 9 feet, particularly across the
offshore Atlantic waters and the Anegada Passage, where a Small Craft
Advisory will be in effect from late tonight through late Friday
night. Mariners should exercise caution, as conditions are expected
to deteriorate late tonight through early in the weekend before
gradually improving.

&&

.BEACH FORECAST...

The moderate risk of rip currents will be in effect through
tonight for the northern and eastern beaches of Puerto Rico as
well as beaches of Culebra, Vieques and the USVI. From Friday and
into the weekend, a high risk of rip currents will prevail for
those areas as swells from Tropical Storm Jerry begin to affect
the local waters. These swells will gradually increase in height
by Thursday night, leading to hazardous surf conditions with
breaking waves up to 6 to 7 feet along exposed beaches. Conditions
are expected to gradually improve to moderate conditions early
next week.

Heed the advice of lifeguards, beach patrol flags and signs. If you
become caught in a rip current, yell for help. Remain calm, do not
exhaust yourself and stay afloat while waiting for help. If you have
to swim out of a rip current, swim parallel to shore and back toward
the beach when possible. Do not attempt to swim directly against a
rip current as you will tire quickly.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory until 4 PM AST this afternoon for PRZ001>005-007-
     008-010>013.

VI...Heat Advisory until 4 PM AST this afternoon for VIZ001-002.

AM...Small Craft Advisory from midnight tonight to 6 AM AST Saturday
     for AMZ711-723.

&&

$$

SHORT TERM/AVIATION...CVB
MARINE/BEACH FORECAST...MMC