textproduct: San Juan

KEY MESSAGES

Issued at 422 AM AST Wed Jan 28 2026

* Relatively stable weather conditions is expected through Friday, with brief morning showers in eastern areas of Puerto Rico and USVI and afternoon showers developing over western Puerto Rico; minor ponding on roads is possible.

* An approaching frontal boundary could bring increasing showers and thunderstorms this weekend into early next week, accompanied by lightning and gusty winds. Flooding threats may increase from limited to elevated, including urban and small stream flooding, especially in areas where heavy rainfall persists.

* For the U.S. Virgin Islands, the potential for heavy rainfall and thunderstorms appears lower this weekend into early next week, as the most active weather is currently expected to remain west of the islands. However, passing showers and isolated thunderstorms are still possible.

* Marine and coastal conditions may become hazardous by early next week, with increasing winds and building seas affecting small craft, along with an elevated rip current risk along north- facing beaches, creating dangerous swimming conditions at exposed locations.

Short Term(Today through Friday)

Issued at 422 AM AST Wed Jan 28 2026

Overnight, relatively calm conditions and mostly clear skies prevailed across the region. Consequently, cool temperatures were observed across Puerto Rico and the U.S. Virgin Islands, with minimums ranging from the upper 60s to low 70s in lower elevations and the upper 50s to low 60s across the higher mountains of Puerto Rico. Passing showers were noted primarily over the Anegada Passage, west of St. Croix, and south of Vieques.

Today, local weather will be influenced by surface high pressure over the central Atlantic and a mid-to-upper-level ridge, maintaining stable and relatively dry conditions aloft. However, a patch of low-level moisture carried by the trade winds will filter into the area, bringing rounds of morning showers to the U.S. Virgin Islands and portions of eastern and northern Puerto Rico, including the San Juan metro area. By this afternoon, activity will shift toward western and northwestern Puerto Rico, driven by daytime heating and orographic effects. Streamer activity is also possible from El Yunque toward the San Juan metro area, potentially resulting in additional afternoon showers. While precipitable water values will start below the climatological normal at 1.30 inches, they are expected to rise to an above-normal 1.75 inches by the afternoon. This setup poses a limited flooding risk, primarily involving ponding on roads and in areas with poor drainage.

A similar pattern is expected Thursday and Friday, with drier air filtering in during the early morning followed by another disturbance that will trigger showers from mid-morning onward. Conditions will become increasingly unstable late Friday into Saturday as moisture from a frontal boundary and tropical moisture from the Caribbean approach the region.

Throughout the short term, temperatures at the 925 mb level will remain slightly above climatological normals. Maximum temperatures are forecast to reach the mid-80s in lower elevations and the mid-to- upper 70s across the higher terrain.

Long Term(Saturday through Wednesday)

Issued at 422 AM AST Wed Jan 28 2026

The synoptic pattern is forecast to remain generally unchanged through the long-term period, with a frontal boundary lingering near the local area. A southerly to southeasterly low-level flow ahead of this boundary will persist, continuing to advect warm and moist air across Puerto Rico and the U.S. Virgin Islands. As a result, above- normal temperatures are expected to persist through the period.

Global model guidance continues to indicate an increase in available moisture beginning Saturday, with precipitable water values rising to near 2.0 inches or higher and remaining above climatological normals through early next week. Low- to mid-level moisture, particularly below 700 mb, is forecast to remain elevated. Although some drying at mid levels (around 700-500 mb) is suggested at times, the overall moisture profile should remain sufficient to support periods of enhanced shower and thunderstorm activity.

At upper levels, the region is expected to remain between an upper- level trough over the western Atlantic and a ridge to the southeast, providing periods of favorable upper-level dynamics depending on the exact placement and evolution of these features. This pattern, combined with persistent low-level moisture convergence along the nearby frontal boundary, will support increasing rainfall coverage, particularly from Sunday through Tuesday.

Recent guidance continues to suggest a signal for above-normal rainfall across portions of the forecast area early next week. Of note, ECMWF Extreme Forecast Index output consistently highlights a rainfall signal several days in advance, which is somewhat surprising given the lead time and suggests increasing ensemble agreement toward a wetter-than-normal pattern. While confidence in the exact timing, magnitude, and spatial distribution of rainfall remains limited at this range, the persistence of the signal supports a continued potential for locally heavy rainfall, especially where showers and thunderstorms repeatedly affect the same areas. Some uncertainty remains with respect to the exact placement of the frontal boundary, as a westward position closer to Hispaniola would result in reduced low-level convergence and consequently less widespread shower and thunderstorm coverage across the local forecast area.

Diurnal heating, local effects, and sea breeze convergence will continue to play a role in convective development each afternoon, depending on the persistence of cloud cover, mainly across interior and western to northwestern Puerto Rico. Potential impacts include ponding of water on roadways, urban and small stream flooding, and localized flooding, particularly in areas that receive repeated rounds of rainfall. Gusty winds may accompany heavier showers or isolated thunderstorms.

Overall, the long-term period is expected to remain unsettled, with the primary concerns being above-normal rainfall and localized flooding potential through at least Tuesday.

AVIATION

(06Z TAFS) Issued at 422 AM AST Wed Jan 28 2026

Mainly VFR conditions expected to prevail across all TAF sites during the next 24 hrs. A patch of low-level moisture surge will increase SHRA aft 28/14Z across eastern PR and the USVI. Later this afternoon SHRA will develop along central PR and spreading toward the northwest portions of PR, affecting TJBQ aft 28/17Z. Periods of reduced VIS and low ceilings can be expected with the strongest activity. East winds will prevail from 10-15 kt with stronger gusts and sea breeze variations aft 28/13-14Z.

MARINE

Issued at 422 AM AST Wed Jan 28 2026

Light to moderate easterly winds will prevail through the end of the week as surface high pressure shifts eastward, with seas generally subsiding across the local waters. By early next week, a northwesterly to northerly long-period swell is expected to reach the regional waters by Monday, combining with increasing winds to produce choppy to rough seas and potentially hazardous marine conditions, including Small Craft Advisory criteria, particularly across the offshore Atlantic waters and passages. An increase in shower and thunderstorm activity is also expected from this weekend into early next week, especially over the northwestern Atlantic waters and the Mona Passage, with lightning and gusty winds possible.

BEACH FORECAST

Issued at 422 AM AST Wed Jan 28 2026

A series of weak northerly swells will continue to reach the Atlantic waters through the week and into the weekend, maintaining a moderate rip current risk along most north-facing beaches of the islands, where life-threatening rip currents are possible. Localized areas of high rip current risk cannot be ruled out, particularly along the most exposed beaches during periods of higher swell energy.

Beach conditions may further deteriorate by early next week due to increasing winds and the arrival of a northwesterly to northerly long-period swell, which could result in more hazardous surf conditions. In addition, showers and thunderstorms, especially from this weekend into early next week, may produce gusty winds, lightning, and rapidly changing conditions, increasing the risk for beachgoers.

For localized and updated rip current information, visit weather.gov/beach/sju.

SJU WATCHES/WARNINGS/ADVISORIES

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