textproduct: San Juan

KEY MESSAGES

Issued at 228 PM AST Sat Jan 31 2026

* The flood risk will persist through midweek. Urban and small stream flooding, localized flash flooding, and minor landslides in areas of steep terrain are possible, particularly from late Sunday through Tuesday. Residents and visitors are urged to avoid small streams, creeks, and other recreational areas near rivers.

* Life-threatening rip currents are expected today across the northern beaches from Rincon to Fajardo, Culebra and the northern USVI. A large, long-period northerly swell and increasing winds will bring hazardous seas and life-threatening rip currents across most waters and coastal areas of the islands from Monday onward. Rough surf and life-threatening rip currents are expected. Beach erosion and minor coastal flooding are likely in the most vulnerable coastal areas.

* Isolated thunderstorms are possible from the weekend into early next week, bringing localized lightning and brief gusty winds.

* Across the USVI, sunny to partly cloudy skies are expected this morning, followed by an increase in cloudiness and shower activity from this afternoon through the rest of the weekend.

Short Term(This evening through Monday)

Issued at 228 PM AST Sat Jan 31 2026

Across Puerto Rico and the U.S. Virgin Islands, overall cloudy skies and humid conditions prevailed throughout the day. During the morning hours, showers affected Saint Croix and southern portions of Puerto Rico. By the early afternoon, shower activity shifted across the interior and eastern sections of Puerto Rico, with additional rain bands filtering over southern Puerto Rico from the Caribbean waters later in the afternoon. Through 230 PM AST, radar estimates and non-official surface observations indicated rainfall accumulations ranging from approximately 1.0 to 1.6 inches. Despite persistent cloud cover and passing showers, temperatures remained in the upper 80s along coastal areas, while cooler readings in the 70s were observed across the interior.

The 31/12Z sounding depicts moist low levels with a dry layer between 700-500 mb; however, this dry mid-level air is already eroding, as shown by the GOES satellite imagery, which indicates mid- level moisture lifting over the region. This supports continued top- down moistening of the column through the period. Precipitable water values will increase to well above normal levels, locally approaching two standard deviations above climatological normal.

The synoptic pattern is characterized by a polar trough at upper levels and an associated frontal boundary northwest of the region, along with a deep-layer ridge to the east, maintaining persistent southerly low-level flow today and Sunday. This southerly flow will favor the clustering of showers and isolated thunderstorms across southern portions of Puerto Rico and potentially the southern U.S. Virgin Islands through Sunday, supported by enhanced low-level moisture convergence. Upper- level support remains modest but sufficient to sustain periods of showers, with locally heavier activity possible where convergence persists. Late Sunday night into early Monday, a col ahead of the approaching frontal boundary is expected to move across the region, resulting in a temporary decrease in wind speeds.

By Monday, low-level winds are expected to increase again and veer more northerly as the frontal boundary approaches and moves over the area. This change in the low-level flow will favor a northward shift in shower and isolated thunderstorm activity, with increasing coverage across northern portions of the CWA. ECMWF Extreme Forecast Index guidance supports this evolution, with EFI values increasing from modest levels today to higher values on Sunday and peaking on Monday, reflecting increased ensemble weighting toward the wettest solutions.

Potential impacts through the period include ponding of water on roadways, urban and poor-drainage flooding, localized small-stream rises, and reduced visibility in heavier showers. Gusty winds may accompany stronger showers or isolated thunderstorms. Overall, the short-term period is expected to remain unsettled, with the primary concerns being above-normal rainfall and localized flooding potential, particularly from Sunday into Monday.

Long Term(Tuesday through next Friday)

Issued at 240 AM AST Sat Jan 31 2026

The frontal boundary is expected to linger near the local area through midweek, as a weak area of high pressure rolls from the western Atlantic and passes just north of the area into the central Atlantic by the end of the workweek. A series of deep- layer lows/troughs will continue to move from the western into the north-central Atlantic, promoting colder than normal 500 mb temperatures and favorable conditions for thunderstorm development on Wednesday and Thursday. Another approaching front is expected to reach the local area once again by Saturday. These weather features will keep higher than normal moisture content over the islands, and a wet and unsettled weather period is expected to prevail through the long-term period. Therefore, if the expected weather in the short-term period materializes, any additional excessive period of heavy rainfall over saturated soils will lead to quick flooding and possible minor landslides in areas of steep terrain.

Breezy northeasterly winds will prevail through Wednesday, turning more east to southeasterly from Thursday onward, and becoming light and variable on Saturday as the front moves closer to the region.

AVIATION

(18Z TAFS) Issued at 228 PM AST Sat Jan 31 2026

Mainly VFR conds exp across all TAF sites thru the fcst pd. SCT - SHRA/+SHRA will cont to affect PR/USVI, with brief MVFR/IFR CIGs/VIS psbl at times, particularly southern terminals. Isold TSRA could increase on Sun. S-SE sfc winds 10-15 kt with ocnl higher gusts, weakening aft 31/23z, then incrg again aft 01/13Z.

MARINE

Issued at 228 PM AST Sat Jan 31 2026

A Small Craft Advisory remains in effect for the offshore Atlantic waters as seas continue to reach up to 7 feet. Winds and seas are expected to gradually subside on Sunday. However, by early Monday morning, a large, long-period northerly swell is forecast to arrive, causing seas to build up to around 12 feet and persist through at least midweek. Additionally, an unsettled weather pattern will result in more frequent showers and isolated thunderstorms, which may locally enhance winds and seas, creating hazardous marine conditions and further exacerbating existing hazards., particularly from Sunday onwards.

BEACH FORECAST

Issued at 228 PM AST Sat Jan 31 2026

The lingering northerly swell will continue to promote a high risk of rip currents through 6 AM tomorrow across all northern- facing beaches, including areas from Rincon to Fajardo, Culebra, and the northern U.S. Virgin Islands.

Beginning Monday, a stronger, long-period northerly to north- northwesterly swell is forecast to arrive and persist through the workweek. This swell is expected to once again elevate the rip current risk to high, while also increasing the potential for high surf and minor coastal flooding, particularly during the peak of the event from Monday into Tuesday across exposed Atlantic and northwestern coastlines. Beachgoers are urged to continue monitoring future forecasts as conditions evolve.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through late tonight for PRZ001-002-005- 008-010-012.

VI...High Rip Current Risk through late tonight for VIZ001.

AM...Small Craft Advisory until 6 AM AST Sunday for AMZ711.