Urb San Marcos Puerto Rico Weather Forecast Discussion

947
FXCA62 TJSJ 101757
AFDSJU
Area Forecast Discussion
National Weather Service San Juan PR
157 PM AST Fri Oct 10 2025
.KEY MESSAGES...
* Tropical Storm Jerry will continue to move northeast of the
  region this afternoon before continuing its track towards the
  open Atlantic.Deep tropical moisture from Jerry will help
  support rounds of showers and thunderstorms through the weekend,
  maintaining an elevated risk of flooding, mostly for interior
  and eastern Puerto Rico and the U.S. Virgin Islands.
* Hazardous marine conditions for small crafts and hazardous beach
  conditions are forecast as swells from Jerry continue affecting
  the regional waters through Saturday.
* For the U.S. Virgin Islands, particularly St. Thomas and St.
  John, conditions could deteriorate further as periods of gusty
  winds and locally heavy rainfall are possible this evening into
  the weekend.
&&
.SHORT TERM...Rest of the Afternoon through Sunday...
During the morning hours, mostly clear skies and calm conditions
prevailed across Puerto Rico and the U.S. Virgin Islands. Around
late morning, between 11:30 AM and noon, some cloudiness associated
with Tropical Storm Jerry began spreading over the USVI and eastern
PR. Convective activity began to develop by early afternoon over
eastern portions of Puerto Rico due to the combination of local
effect and diurnal heating leading to heavy showers and isolated
thunderstorms. Expect this activity to persist throughout the
afternoon as it spread over interior Puerto Rico. Winds remained
light and variable as Jerry passed near the area.
Tonight, periods of showers will continue to move across the
islands, with isolated thunderstorms possible, especially over the
U.S. Virgin Islands and eastern Puerto Rico, as Tropical Storm Jerry
continues to move northeast of the region. According to the latest
11 AM update from the National Hurricane Center, Jerry was located
near 20.2N and 63.4W, moving northwest at about 16 mph. Although
the storm will stay well offshore, it will continue to produce
indirect impacts through at least Saturday, including periods of
heavy rain, thunderstorms, and localized flooding. Moisture levels
remain high, with precipitable water values between 2.0 and 2.2
inches above normal for this time of year. This tropical moisture,
combined with weak steering winds, will support slow-moving showers
and thunderstorms capable of producing heavy rainfall and frequent
lightning, particularly during the afternoon and evening hours. An
elevated flood risk is expected through Saturday, especially across
eastern and interior Puerto Rico and the U.S. Virgin Islands.
Rainfall totals of 2 to 4 inches are expected in these areas, with
isolated higher amounts up to 6 inches possible over the mountains
and in areas of persistent showers. This could lead to localized
flash flooding, particularly in urban areas and steep terrain.
Aside from the rain, heat, and humidity will continue to make
conditions uncomfortable at times. If skies clear between showers,
temperatures and humidity could combine to produce a limited to
elevated heat risk, depending on local cloud cover and rainfall
associated with Tropical Storm Jerry.
By Sunday, conditions should gradually return to a more typical
weather pattern as Jerry moves farther away. Moisture levels are
expected to decrease to near or slightly below normal values, though
lingering humidity and southeasterly winds will still bring warm and
humid conditions. Afternoon showers and thunderstorms are likely to
redevelop over interior and northwestern Puerto Rico due to local
sea breeze effects.
Residents and visitors should continue to monitor official updates
from the National Hurricane Center and the National Weather Service
in San Juan for the latest information on Tropical Storm Jerry and
its effects on the local area.
.LONG TERM...Monday through Friday...
.PREV DISCUSSION... /issued 537 AM AST Fri Oct 10 2025/
Drier air will filter in to start the workweek under easterly flow,
displacing the moisture plume related to Jerry. Patches of below
normal to above normal moisture will filter over the islands Tuesday
through Wednesday and then gradually increasing during the second
half of the workweek. Mid to upper level ridging will be present to
start the period, however model guidance has an upper level low
approaching the Caribbean by midweek. Latest runs have backed off on
the deep level trough digging down towards the Caribbean during the
second half of the period. However, as its surface low moves towards
the northwestern Atlantic and a high positions itself over the
eastern tropical Atlantic, steering flow will become southeasterly
on Tuesday, southeasterly to southerly on Wednesday and southerly
through most of the rest of the period. PWAT values are forecast to
gradually increase Thursday and Friday as both moisture from a
frontal boundary approaches from the north and southerly flow steers
tropical moisture over the region, these features can bring above 2
inches of PWAT to end the forecast period. Flooding risk remains,
particularly during afternoon convection steered by the above
mentioned 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. Surface winds will be
generally light to moderate through Tuesday, becoming light
Wednesday onwards as the southerly component establishes itself.
This southerly component will also aid in sustaining a heat risk
during the period. Low concentrations of Saharan Dust will also be
present to start the workweek.
&&
.AVIATION...
(18Z TAFS)
VFR conds across all TAFs sites. However, brief periods of MVFR
conditions are possible in SHRA/TSRA this aftn, mainly TISX and
TIST, then over TJSJ, TJBQ, and TJPS. Reduced VIS expected near the
heaviest rainfall activity. Additional bands of SHRA through the
overnight hours. Light and variable winds should remain thru
Saturday as TS Jerry moves NE of the area.
&&
.MARINE...
Tropical Storm Jerry continues to move northeast of the islands.
This system will continue moving northwestward at a safe distance
from Puerto Rico and the USVI. Although no direct tropical storm
impacts are expected, indirect marine impacts will continue
spreading across the regional waters from late tonight and
Saturday. 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 is in effect
through tomorrow morning. Conditions are forecast to gradually
improve late Saturday onwards.
&&
.BEACH FORECAST...
A high risk of rip currents will be in effect this evening for
the beaches of the USVI, Vieques, Culebra, and eastern and
northern Puerto Rico as swells from Tropical Storm Jerry begin to
affect the local waters. These swells can lead to large breaking
waves up to 6 to 7 feet along exposed beaches. Conditions are
expected to gradually improve to a moderate risk of rip currents
by tomorrow evening.
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...High Rip Current Risk from 6 PM AST this evening through
     Saturday afternoon for PRZ001-002-005-008-012-013.
VI...High Rip Current Risk through Saturday afternoon for VIZ001-002.
AM...Small Craft Advisory until 6 AM AST Saturday for AMZ711-723.
&&
$$
SHORT TERM/AVIATION...MMC
MARINE/BEACH...CVB

NWS SJU Office Area Forecast Discussion