678
FXCA62 TJSJ 171848
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
248 PM AST Sun May 17 2026

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

.KEY MESSAGES...
Issued at 248 PM AST Sun May 17 2026

* An upper-level trough approaching the islands today will
  increase the frequency of showers and isolated thunderstorms,
  particularly across the interior and western PR. Limited to
  elevated flooding risk.

* A limited heat risk will continue this upcoming week, heat
  indices expected near the mid 90s to low 100s across urban and
  coastal areas.

* Breezy conditions will maintain choppy seas. A Small Craft
  Advisory is now in effect for the offshore Atlantic waters
  through at least Monday afternoon.

* A moderate risk of rip currents will persist this week, mainly
  along the north and east facing beaches of Puerto Rico (southern
  beaches at times), as well as beaches of Vieques, Culebra, and
  the U.S. Virgin Islands.

&&

.Short Term(This evening through Tuesday)...
Issued at 248 PM AST Sun May 17 2026

The morning has featured partly cloudy skies with quick-moving
passing showers across windward areas of Puerto Rico. Breezy to
windy conditions have been observed at local surface weather
stations, with easterly winds around 15 to 20 mph and gusts
reaching the upper 20s to lower 30s mph. Daytime highs have
generally ranged from the upper 80s to lower 90s across urban and
coastal areas and from the upper 70s to lower 80s across higher
elevations of the islands. Heat indices have generally ranged
from the mid 90s to around 100 to 102 degrees F.

This afternoon, expect scattered to numerous showers and
thunderstorms across the northwestern quadrant of Puerto Rico. A
Flood Advisory has already been issued for Aguada, Anasco, Las
Marias, Moca, Rincon, and San Sebastian until 530 PM AST. Impacts
include minor flooding in low-lying and poor drainage areas.

East to east-southeast winds will continue transporting tropical
moisture across the islands as surface high pressure over the
Atlantic promotes breezy easterly winds, particularly across
coastal areas. Moisture levels will remain near climatological
normals through most of the short-term period, except on Monday,
with localized increases during afternoon convection. An
amplifying upper-level trough approaching from the west will
slightly enhance instability and support periods of showers and
isolated thunderstorms across the region.

Late tonight and early Monday morning, an area of cloudiness and
trade wind showers will continue moving across the U.S. Virgin
Islands and windward sections of Puerto Rico before drier air
filters into the area later in the day. Guidance suggests a
gradually drier air mass will enter the region on Monday, with
PWAT values falling to near or below 1.5 inches by the afternoon.
Although somewhat drier air is expected Monday afternoon, daytime
heating, local orographic effects, sea breeze convergence, and
upper-level support will still promote scattered convection across
interior and western Puerto Rico. Isolated thunderstorms may
develop and produce heavy rainfall, resulting in ponding of water
on roads and poorly drained areas, as well as localized urban and
small stream flooding. Flood advisories may be required in some
locations. By Tuesday, moisture levels are expected to return
closer to normal, with a similar weather pattern continuing across
the area.

925 mb temperature guidance indicates temperatures trending closer
to seasonal values early this week. As a result, a limited heat
risk will persist through Monday and Tuesday, with heat indices
slightly cooler expected compared to recent days.

&&

.Long Term(Wednesday through Sunday)...
Issued at 455 AM AST Sun May 17 2026

A typical late spring to early summer weather pattern is expected
through the long-term period. Broad surface high pressure over the
northwestern Atlantic will maintain moderate to fresh east to east-
southeasterly winds across the local islands, with occasionally
strong winds at times. Winds are expected to strengthen further into
next weekend, supporting breezy to locally windy conditions.
At mid and upper levels, the area will remain between ridging to the
southeast and a lingering trough/low over the western Atlantic,
while weak disturbances move around the broader pattern and approach
the northeastern Caribbean. This pattern will help support periods
of increased instability and more favorable conditions for deeper
afternoon convection late in the week and into the holiday weekend.

Patchy moisture embedded within the trade winds will continue to
promote passing showers during the overnight and morning hours each
day, followed by afternoon showers and isolated thunderstorms mainly
across interior and western to northwestern areas. Although mid-
level conditions may remain somewhat marginal at times, the
combination of local effects and strong daytime heating should still
support deeper convection each afternoon. Flooding concerns are
expected to gradually increase and become more locally elevated late
in the week and into the holiday weekend, with locally heavy
rainfall, ponding of water on roads, and localized urban and small
stream flooding possible. Additional hazards will include lightning,
heat, and gusty winds, especially as outdoor activity increases
during the Memorial Day weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 248 PM AST Sun May 17 2026

VFR conditions are expected across all TAF terminals, except at
TJBQ due to VCTS/TSRA thru ~17/22Z. Breezy to windy conditions
from the E to SE becoming more variable overnight at around 5 to
10 kts. VCSH/-SHRA over TIST, TISX, TJSJ are possible aft 18/06Z
From 18/14Z, winds are expected to increase again and VCTS/TSRA
are possible across TJBQ aft 18/17Z.

&&

.MARINE...
Issued at 248 PM AST Sun May 17 2026

A broad surface high pressure over the central Atlantic will
promote moderate to locally fresh east to east-southeasterly winds
across the regional waters through at least today. From late
today into early next week, winds will turn more easterly as
another surface high pressure builds over the western Atlantic.
These breezy conditions will maintain choppy seas, particularly
across the offshore and exposed Atlantic and Caribbean waters. A
Small Craft Advisory is now in effect for the offshore Atlantic
waters through Monday afternoon. Afternoon and early evening
isolated thunderstorms can be expected each day across the
northwestern waters of Puerto Rico.

&&

.BEACH FORECAST...
Issued at 248 PM AST Sun May 17 2026

A moderate risk of life-threatening rip currents will continue to
prevail across the east, north, and southern beaches of Puerto
Rico, Culebra, Vieques and the U.S. Virgin Islands during the next
several days. Beachgoers should exercise caution when entering
these beaches. This means life-threatening rip currents are
possible in the surf zones, and beachgoers should exercise caution
when entering these beaches.

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. For additional
information and location-specific rip current details, visit
weather.gov/beach/sju.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory until 6 PM AST Monday for AMZ711.

&&

$$

SHORT TERM/AVIATION...YZR
LONG TERM...ICP
MARINE...DS
BEACH FORECAST...GRS

NWS SJU Office Area Forecast Discussion