071
FXCA62 TJSJ 022103
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
503 PM AST Wed Apr 2 2025

.SYNOPSIS...

A Wind Advisory is in effect for Puerto Rico and the U.S. Virgin
Islands, especially across windward coastal areas through Friday
night due to winds between 20 and 30 mph and frequent gusts
between 30 and 40 mph, but up to 50 mph. Tomorrow and Friday are
expected to be the windiest days, maintaining hazardous marine and
coastal conditions. Small Craft Advisories and a High Rip Current
Risk are also in effect at least through next Saturday.
Easterlies will bring patches of moisture with embedded rain
showers each day. Therefore, we cannot rule out periods of
moderate to locally heavy rain at times.

&&

.SHORT TERM...Tonight through Friday...

We issued a Wind Advisory due to breezy to windy conditions. The
meteorological network detected frequent wind gusts, with the
maximum gusts near Culebra, St Thomas, and St John, between 40 and
45 mph. Generally, the maximum wind gust observations range
between 30 and 40 mph across Puerto Rico and the US Virgin
Islands. Showery weather prevailed today, mainly across the
windward locations, moving westward by the mid-morning into the
afternoon. Periods of moderate to locally heavy rain produced
ponding of water in roads and poorly drained areas, especially
over the border between Mayaguez and Anasco where totals reached
around 2 to 2.75 in. Maximum values reached the upper 80s, mainly
across the coastal locations.

Breezy to windy trade winds will prevail through at least Friday
evening, peaking on Thursday, as model guidance indicates. This
increasing wind trend is due to a strong above-normal surface high
pressure anchored north of the islands across the Atlantic Ocean,
which tightens the local pressure gradient. Thus, the Wind Advisory
is in effect until Friday night due to winds between 20 and 30 mph
and frequent gusts between 30 and 40 mph, but up to 50 mph. On the
other hand, the easterlies will bring patches of moisture with
embedded rain showers each day. Therefore, we cannot rule out
periods of moderate to locally heavy rain at times.

PLease refer to the latest URGENT - WEATHER MESSAGE (NPWSJU) for
more information about the WIND ADVISORY. A Public Information
Statement (PNSSJU) was issued around noon with the highest wind
gusts reports, we plan to issue another PNSSJU at around 900 PM
AST.

.LONG TERM...Saturday through Wednesday...
./FROM PREV DISCUSSION...Issued at 500 AM AST Wed Apr 2 2025/

At the beginning of the long-term period, conditions will remain
breezy but are anticipated to follow a decreasing trend. At the
same time, this will allow hazardous marine and coastal conditions
to gradually improve, at least from Saturday night through at
least next Monday.

Model guidance continues to suggest that a surface high-pressure
system over the western Atlantic will move eastward into the
Central Atlantic, promoting east to northeast winds through
Sunday. These winds will then become more easterly early next
week. Meanwhile, a mid-level ridge will dominate to the north and
west of the forecast area, while troughing develops and persists
over the region through the forecast period. This will promote
ventilation and cooler temperatures aloft, with 500 mb temperatures
remaining between -8C to -10C by the weekend. These conditions
will support favorable conditions for deep convection and increase
the chances of thunderstorm development. However, a significant
drop in moisture content across different levels of the atmosphere
is expected to inhibit significant rainfall and afternoon
thunderstorms. The latest models still show uncertainty and
disagree on the amount and timing of precipitation at this moment
and we will continue to monitor and adjust the forecast accordingly.

Throughout the forecast period, the latest models suggest that
precipitable water values will oscillate between below 1.0 and 1.5
inches, which is considered below normal to near average. As a
result, activity will likely depend on the arrival of patches of
moisture, leading to periods of sunshine and passing showers.
Isolated to scattered showers, with a thunderstorm or two, cannot
be ruled out during the afternoon hours across the western
portions of Puerto Rico, but at the moment, significant accumulations
are not expected.

&&

.AVIATION...

(18Z TAFs)

VFR conditions will prevail, but SHRA/+SHRA could sometimes impact
local terminals, producing brief MVFR or IFR conditions, especially
across windward locations. Winds will remain mainly from the E at 20-
25 kt, with gusts between 30 and 40 knots, but could be higher.
Winds from the E/ENE will be around 15 knots after 02/13z overnight
but will increase again tomorrow after 03/13z. Thus, a Wind Advisory
is in effect for the islands.

&&

.MARINE...

A surface high pressure over the Atlantic basin will continue to
promote fresh to locally strong easterly winds throughout the week.
Thursday and Friday are expected to be the windiest days of the week.
Seas will continue to build between 6 and 9 feet, and occasionally
higher, across the regional waters. As a result, hazardous seas are
anticipated through the forecast period. Isolated to scattered
shower activity will continue over the next few days. Small Craft
Advisories are currently in effect, please refer to the latest
Marine Weather Message (MWWSJU) and Coastal Waters Forecast
(CWFSJU) for more information.

&&

.BEACH FORECAST...

Strong winds are deteriorating coastal conditions. Through
at least Saturday afternoon, there is a high risk of rip currents
for the north-facing beaches of Puerto Rico, from Aguadilla to
Fajardo, Culebra and the U.S. Virgin Islands. For tomorrow morning
through at least Friday evening there will be a high rip current
risk for the beaches of southeastern Puerto Rico, from Salinas to
Yabucoa, and Vieques. A moderate risk is in place for most other
beaches. Please refer to the latest Coastal Hazard Message
(CFWSJU) and Surf Zone Forecast (SRFSJU) for more information.

Rip currents are powerful channels of water flowing quickly away
from shore, which occur most often at low spots or breaks in the
sandbar and in the vicinity of structures such as groins, jetties
and piers. They can sweep even the best swimmers away from shore
into deeper water, where it becomes difficult to return to safety.
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 through Saturday afternoon for PRZ001-002-
     005-008-012.

     Wind Advisory until 8 PM AST Friday for PRZ001>013.

     High Rip Current Risk from Thursday morning through Friday
     evening for PRZ003-013.

VI...High Rip Current Risk through Saturday afternoon for VIZ001-002.

     Wind Advisory until 8 PM AST Friday for VIZ001-002.

AM...Small Craft Advisory until noon AST Saturday for AMZ711-712-716-
     723-726-733-741.

     Small Craft Advisory until 6 AM AST Friday for AMZ735-742-745.

&&

$$

SHORT TERM...ICP/CAM
LONG TERM....MRR

NWS SJU Office Area Forecast Discussion