National Weather Service Today's Weather Impact Levels

576
FXCA62 TJSJ 201815
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
215 PM AST Thu Nov 20 2025

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

.KEY MESSAGES...
Issued at 215 PM AST Thu Nov 20 2025

* There is a High Risk of Rip Currents for the north-facing
  beaches in Puerto Rico, Culebra, and eastern half St. Croix
  until 6 PM AST this evening.

* Residents and visitors in the USVI and PR can expect pleasant
  temperatures as a cooling trend will prevail, especially from
  Friday into next week.

* Afternoon showers and possible t-storms are forecast mainly over
  interior to SW Puerto Rico tomorrow.

&&

.Short Term(This evening through Saturday)...
Issued at 215 PM AST Thu Nov 20 2025

Weather conditions during the morning hours remained relatively
calm with mostly clear skies across Puerto Rico and the U.S.
Virgin Islands. By the afternoon, shower and thunderstorm activity
developed over the southwestern quadrant of Puerto Rico. Winds
were generally from the northeast, keeping coastal temperatures in
the 80s, with a few isolated coastal and urban areas reaching the
low 90s, while temperatures across higher terrain remained in the
70s.

A generally quiet night is expected as daytime heating diminishes
and convection fades. However, brief, shallow trade wind showers
will still reach portions of eastern Puerto Rico and the U.S.
Virgin Islands. Light to moderate northeast winds will persist,
and temperatures will cool into the mid-70s along the coasts and
the 60s across the interior and higher elevations.

As mentioned in previous discussions, a second, deeper shortwave is
forecast to drop farther south on Friday, introducing another brief
period of cooling aloft before quickly shifting east of the region.
Subsidence and significant drying will take over the region after
the end of the workweek, with PWAT values falling below typical
levels for this time of year. At the surface, a trough and a
strengthening high over the western Atlantic will reinforce northeast
trade wind flow, pushing increasingly drier air across the
region. The latest model guidance suggests that a gradual mid-
level ridge will strengthen the trade-wind cap inversion, resulting
in increasingly unfavorable conditions for deep convection.
Although isolated overnight trades may still occur, the rainfall
risk remains limited for tomorrow. Regardless, we anticipated a
significant reduction in afternoon convection compared to recent
days. As a heads up, temperatures will begin to trend slightly
cooler, moderated by persistent northeast winds.

Conditions will turn more stable on Saturday as drier air deepens
and the mid-level inversion strengthens further. The latest model
guidance suggests that values will remain well below normal,
supporting a notably drier and more stable pattern. Only isolated,
brief trade wind showers are expected overnight and early morning,
with little to no afternoon convection. Temperatures will remain
slightly cooler, especially overnight under clearer skies. Overall,
hazard risks will decrease significantly, with only a limited chance
of thunderstorms or localized flooding on Friday, and little to no
risk by the weekend.

&&

.Long Term(Sunday through next Wednesday)...
Issued at 458 AM AST Thu Nov 20 2025

Forecast confidence remains low to moderate due to notable
discrepancies between the GFS and ECMWF regarding the evolution of
mid- to upper-level features early next week. These differences
directly affect expectations for instability and convective
coverage across Puerto Rico and the U.S. Virgin Islands.

The GFS suggests a short-wave trough replacing the zonal flow
aloft Sunday into Monday, followed by additional amplification on
Tuesday. This scenario would shift a mid-level ridge westward over
the Bahamas/Cuba, placing PR/USVI between the ridge to the west
and a deepening trough to the east, favoring increased upper-level
divergence and a more unstable environment. Under this
configuration, the probability of scattered afternoon convection
and isolated thunderstorms would be moderate (20-40%), peaking
Tuesday through the middle of the week.

In contrast, the ECMWF maintains a more stable pattern, with
zonal flow on Sunday and only weak short-wave perturbations on
MondayTuesday. Notably, the model retains the mid-level ridge,
supporting dry air intrusions and subsidence that would limit
convective development. Under this solution, afternoon showers
would be more isolated (2030%), primarily driven by local sea-
breeze and orographic effects. Given these differences, the
forecast leans on a climatological trade- wind pattern. Therefore,
expect periodic patches of moisture embedded in the trades
producing passing showers across the local waters, USVI, and
windward/eastern Puerto Rico. Each afternoon, isolated to
scattered convection (mainly interior and western PR) remains
possible, but the probability of thunderstorms stays low to
moderate (1030%), highest if the GFS scenario materializes.

Overall, no strong signal is emerging for widespread rainfall or a
significant instability event at this time, and uncertainty
remains elevated until better model consensus develops.

Local temperatures will continue to cool, remaining slightly below
normal, around the 25th percentile compared to November
climatology.

&&

.AVIATION...
(18Z TAFS)
Issued at 215 PM AST Thu Nov 20 2025

Mainly VFR conditions for the terminals with brief MVFR conditions
possible mainly over TJPS due to TSRA through 20/21Z. SHRA or
possible TSRA at or in the VCTY of TIST/TISX/TJSJ during the
afternoon hours followed by overnight with passing SHRA over
northern terminals. Steering flow from the northeast up to 15 kts
with higher gusts and sea breeze variations through 20/22Z, bcmng
light and VRB through 21/13Z.

&&

.MARINE...
Issued at 215 PM AST Thu Nov 20 2025

A long period north-northeasterly swell will continue to move across
the local waters through this evening. An upper-level short-wave
trough will help to promote afternoon thunderstorms across the Mona
Passage and Caribbean waters. The remnants of the frontal boundary
will slowly dissipate across the western Atlantic through Friday,
when a surface high is expected to build over the region. This high
pressure will promote moderate trade winds from the upcoming weekend
into early next week.

&&

.BEACH FORECAST...
Issued at 215 PM AST Thu Nov 20 2025

A High Risk of Rip Currents will be in effect through 6 PM AST
this evening for the northern exposed beaches of Puerto Rico and
Culebra, as well as eastern St. Croix, due to lingering energy
from a fading north- northeasterly swell. A moderate risk of rip
currents is forecast for the rest of the workweek and into the
weekend. However, another north-easterly swell is likely to
increase the rip current risk to high again by Tuesday.

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. 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 until 6 PM AST this evening for PRZ001-002-
     005-008-012.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ002.

AM...None.
&&

$$

MMC/MRR

NWS SJU Office Area Forecast Discussion