textproduct: San Juan

KEY MESSAGES

Issued at 334 AM AST Sun Nov 16 2025

* Slow-moving showers and thunderstorms will increase flooding and lightning risk over northern portions of Puerto Rico this afternoon.

* More frequent showers and isolated thunderstorms are likely late this afternoon and tonight over the U.S. Virgin Islands.

* Low to moderate risk of rip currents will prevail today, followed by a high risk along north and east- facing beaches of Puerto Rico and the U.S. Virgin Islands from Monday through Wednesday.

Short Term(Today through Tuesday)

Issued at 334 AM AST Sun Nov 16 2025

Satellite and Doppler Radar imagery detected showers and thunderstorms, mainly across the local waters. Some of these moved over St. Thomas, St. John, and the Adjacent Islands, while the rest of the islands experienced little to no rain. A mid-to-upper-level cloud layer moved over the islands around midnight, primarily creating cloudy skies, which dissipated across most land locations by early Sunday morning. Minimum temperatures dropped into the low to mid-70s along the coastal areas, to the low to mid-60s in the mountains and valleys. Winds were calm to light and variable overnight, influenced by land breeze variations along the coast.

A dissipating surface trough north of the islands and very light winds will keep todays weather pattern slow moving, while a mid to upper level trough overhead maintains an unstable atmosphere supportive of strong showers and thunderstorms. Although peak instability is expected during the morning hours, the most active period is still anticipated this afternoon, additionally driven by diurnal heating and sea breeze convergence. Moisture levels should remain near typical values, with the deeper moisture plume staying north of the region, but the very weak steering flow will allow storms to drift slowly and produce heavy downpours, frequent lightning, and localized flooding, beginning across the interior and later spreading mainly into northern Puerto Rico. This setup will support a limited lightning risk and a limited to elevated flood risk for today. Although temperatures will be warmer than normal, there are no heat concerns. Conditions should gradually improve tonight as slightly more stable air moves in from the subsidence side of the trough.

A high pressure system over the North Atlantic will bring gentle easterly to southeast winds, while a weak mid level ridge helps maintain slightly drier air aloft on Monday. This will lead to fewer and more isolated showers and thunderstorms, even during peak heating hours, with afternoon activity favoring the central interior and the northwestern quadrant. Most of this activity will remain confined to the daytime hours, with Monday night staying mostly quiet as stable and relatively drier conditions limit shower development. On Tuesday, winds shift from the east northeast as another pre frontal trough sets up to the north and cooler temperatures aloft begin to return ahead of the next upper level trough. Even so, moisture will stay on the low side during the day and mid level temperatures will not cool enough to support widespread development, keeping most activity limited and clustered over the central interior to west southwest sections during the afternoon. By Tuesday night, a modest increase in moisture associated with the remnants of a frontal boundary, combined with gradually increasing instability aloft, will support a bit more activity compared to the previous night. Overall flooding risk will remain in the limited category on both Monday and Tuesday due to reduced moisture and slightly more stable conditions. Although temperatures will be warmer than normal, heat will not pose any concerns.

Long Term(Wednesday through Sunday)

Issued at 334 AM AST Sun Nov 16 2025

No major changes were introduced to the long-term forecast, as weather conditions are expected to gradually improve over the period. A polar trough should deepen sufficiently into the tropics, cooling mid-level temperatures (between -8 and -9 degrees Celsius) and increasing stability aloft. Additionally, the latest model guidance suggest that the remnants of a frontal boundary should move across the region by Wednesday, increasing moisture content. Although the deterministic guidance of the GFS and ECMWF suggests that Precipitable Water values will remain seasonal (1.6 - 1.8 inches), showers and isolated thunderstorms should increase flooding and lightning potential, particularly over portions of interior and southwestern Puerto Rico. Rainfall accumulations will likely promote ponding of water over roadways, urban and poorly drained areas, with isolated urban and flooding risk. By Friday, a surface high-pressure system should build over the western Atlantic and mainly promote winds with a northerly component. Additionally, winds are very likely to increase, promoting locally breezy conditions mainly over the coastal areas of the islands. For the upcoming weekend, patches of moisture will move occasionally across the islands, with mostly passing showers across the local waters and passages, moving over windward sections in the morning hours and afternoon convection over interior and southern portions of Puerto Rico.

From the latest deterministic guidance, both GFS and ECMWF suggest a tendency of 925 mb temperatures to decrease during the period. Although ECMWF is warmer, both model solutions suggest temperatures below climatological normal (below 20 degrees Celsius). Given the expected weather conditions and temperatures, the heat risk will remain low during the period.

AVIATION

(06Z TAFS) Issued at 334 AM AST Sun Nov 16 2025

Mainly VFR conds will prevail across most TAF sites through the period. Brief SHRA and isolated TSRA may approach n PR and USVI terminals through 16/13Z. Additional rounds of SHRA/TSRA are possible this afternoon, mainly between 16/16Z22Z, which may lead to short-lived MVFR conds across most PR terminals. Improving conds expected aft 16/22Z with only ltd SHRA overnight. Winds VRB to light early, increasing to 510 kt between 16/13Z22Z, dominated by sea- breeze influences. Higher gusts psbl in and near SHRA/TSRA.

MARINE

Issued at 334 AM AST Sun Nov 16 2025

Due to the proximity of a pre-frontal trough northeast of the region, a variable light to gentle breeze will persist today, becoming moderate by Monday night. Pulses of northerly swells and increasing easterly winds will likely deteriorate marine conditions on Monday through Wednesday. In the meantime, strong showers and isolated thunderstorms could generate locally hazardous conditions for small craft.

BEACH FORECAST

Issued at 334 AM AST Sun Nov 16 2025

Today, theres a moderate risk of rip currents mainly over northern and eastern beaches of Puerto Rico, including Culebra, and the U.S. Virgin Islands, while the rest of the beaches remain under low risk. Under a moderate risk, isolated stronger rip currents may occur elsewhere, especially near piers, jetties, and channels. Beachgoers are urged to exercise caution and swim near a lifeguard. Additionally, afternoon thunderstorms could produce lightning and gusty winds, beachgoers should remain weather alert and seek for shelter whenever they hear thunder.

Pulses of a north-northeasterly swell will deteriorate beach conditions by Monday, increasing the risk of rip currents through at least Wednesday.

SJU WATCHES/WARNINGS/ADVISORIES

PR...None. VI...None. AM...None.