textproduct: San Juan

KEY MESSAGES

Issued at 113 AM AST Mon Sep 28 2026

- There is a HIGH rip current risk statement out for those northern and eastern beaches of PR, as a small northerly swell filters across the regional waters. Therefore, tourist and visitors are urged to exercise caution and avoid beaches in those areas through at least Tuesday morning.

- Heat risk for today and the next few days should be limited, as easterly trade winds strengthen, allowing only localized areas across the US Virgin Islands and Puerto Rico to briefly experience periods of near advisory criteria.

- Expect, a limited flooding risk mainly over northwestern PR, due to previous rains and additional is forecast to develop aross that area today into the end of the workweek.

- Weather conditions are anticipated to change by Friday. Therefore, we urge people to continue to monitor our forecast.

Short Term(Today through Wednesday)

Issued at 113 AM AST Mon Sep 28 2026

Overnight, generally calm weather conditions prevailed across the islands, with partly cloudy skies and a few passing showers mainly affecting eastern and southern Puerto Rico. Rainfall accumulations remained minimal, with no significant impacts observed. Winds were mostly from the east-southeast and light.

As mentioned in previous discussions, expect a more seasonal weather pattern to prevail as model guidances continues to suggest normal to below- normal precipitable water and dry air at the mid levels. A few passing showers will filter across the windward areas of Puerto Rico and the US Virgin Islands during the morning hours, followed by afternoon showers developing mainly from the western interior into northwestern Puerto Rico. Streamers may also produce localized showers downwind from El Yunque and the smaller islands. Overall, today should offer the most favorable day of the short- term period, with partly to mostly sunny skies and limited shower coverage across much of the area. The heat risk for today remains limited as mostly localized areas will experience heat near advisory criteria. Where heavier afternoon showers develop, brief downpours could result in ponding on roads and in poor drainage areas, but the flooding threat remains limited.

Strengthening easterly winds will carry patches of trade-wind moisture across the region, leading to a more variable weather pattern, particularly on Tuesday. Passing showers will become more frequent across the US Virgin Islands, eastern and northeastern Puerto Rico overnight and Tuesday morning. By the afternoon, local and diurnal effects should promote additional shower development across the interior and western portions of Puerto Rico, while streamers could affect areas downwind from El Yunque and the smaller islands. Tuesday appears to be the most active day of the short- term period in terms of the potential for shower frequency and coverage, rather than thunderstorm intensity. Although isolated thunderstorms remain possible, relatively dry mid-level air, gradually warming temperatures aloft, and less favorable lapse rates should limit the depth and organization of convection. Stronger steering winds should also keep showers moving, reducing the potential for prolonged rainfall. Nevertheless, repeated or heavier showers could produce localized ponding and reduced visibility on roadways, particularly across eastern Puerto Rico during the morning and western Puerto Rico during the afternoon.

Wednesday will remain breezy under moderate to locally fresh easterly trade winds. Periods of passing showers are expected across windward areas during the overnight and morning hours, followed by locally induced afternoon showers over western Puerto Rico. However, warming temperatures aloft and weakening mid-level lapse rates should increasingly limit the depth and organization of afternoon convection. Brief heavy rainfall cannot be ruled out, but showers should generally move quickly, keeping the flooding threat limited. Gusty winds may accompany the stronger showers, particularly across exposed coastal locations.

The heat threat during the short term period should be mostly limited as stronger easterly winds provide better ventilation and passing clouds and showers offer occasional relief. Nevertheless, periods of uncomfortable heat remain possible across urban, coastal, and lower-elevation areas. Residents and visitors spending extended periods outdoors should continue to stay hydrated and take breaks from the heat.

Long Term(Thursday through Monday)

Issued at 113 AM AST Mon Sep 28 2026

No major changes were introduced to the long-term forecast, with unstable conditions returning by the end of the week. As mentioned in the previous discussion, a surface high pressure building over the Western Atlantic should promote an easterly-southeasterly wind flow throughout most of the period. Breezy conditions are likely on Thursday, particularly across coastal areas of the islands, though winds may weaken by Friday as model guidance suggests a surface trough interacting with the surface high, strengthening back by Sunday. In the mid and upper levels, the interaction between the ridge over the Hispaniola and a TUTT over the Leeward Islands should bring more stable conditions as the CWA continues under the subsidence side of the trough on Thursday. Afternoon convection can still be expected, though showers should be progressive with short- lived thunderstorms. A transition to a seasonal weather pattern with unstable conditions is expected by Friday, with abundant tropical moisture pooled into the region and upper-level troughs near the area. As mentioned in the previous discussion, the deterministic guidance of the ECMWF and GFS suggests an increase in PWAT values most likely to range between 1.8 and 2.0, normal for this time of year. Taking a look at the cross-section, moisture content in the low to mid levels should increase to near above climatological normal (between 60 - 80%), with guidance suggesting skinny sounding profiles with weak inversion caps. In terms of instability, the presence of the trough should introduce cooler air in the mid levels (500 mb temperatures down to -7.5 C) and divergence aloft, favorable for deeper convection. This pattern should persist on Saturday as well, improving by Sunday as a drier airmass filters into the region and limits deep convection. Overall, afternoon convection is expected each day, particularly across interior and western/northwestern Puerto Rico, along with the local island streamers. Windward sections of the islands can expect isolated to scattered showers during the night and morning hours, though the eastern side of Puerto Rico could have additional rainfall due to streamers during the afternoon. Although the weather conditions do not seem optimal for flooding, ponding of water over roadways and poorly drained areas can be expected on Thursday. On the other hand, the flooding threat should increase on Friday and Saturday, with urban and small stream likely across the aforementioned areas, without ruling out the San Juan Metro Area. For the moment, the flooding threat should remain low on Sunday. In addition to flooding, thunderstorm activity could produce gusty winds and frequent lightning.

As mentioned in the previous discussion, seasonal to warmer conditions are still on forecast, with above climatological normal 925 mb temperatures during the second part of the workweek. Although afternoon convection may start earlier, temperatures may rise quickly during the morning hours, with heat indices exceeding 100 F across urban and low-lying areas. Therefore, the heat threat will remain limited to elevated throughout the forecast period.

AVIATION

(06Z TAFS) Issued at 113 AM AST Mon Sep 28 2026

Expect VFR conds thru 28/15Z. Aftn SHRA/TSRA development could result in brief VCTS at TJBQ/TJPS btw 28/16-23Z. Brief periods of MVFR psbl across western PR, particularly at TJBQ. E/SE winds around 6 to 10 kt with higher gusts and sea breeze variations thru 28/23Z. However, from 29/00Z winds will gradually bcm more E.

MARINE

Issued at 113 AM AST Mon Sep 28 2026

A small northerly swell will persist across the Atlantic waters and passages today as moderate easterly trade winds gradually strengthen. Choppy conditions will continue across the Atlantic waters and Mona Passage, with locally fresh winds expected by Tuesday night into Wednesday. Periods of showers will remain possible across the local waters, with the more typical afternoon activity and isolated thunderstorms expected near western and northern Puerto Rico. Thunderstorms may produce locally higher winds and seas, lightning, and reduced visibility.

BEACH FORECAST

Issued at 113 AM AST Mon Sep 28 2026

The combination of a northerly swell and strengthening easterly trade winds will bring hazardous beach conditions beginning this morning and continuing through late tonight. A High Rip Current Risk will be in effect from northwestern through northeastern Puerto Rico, including the San Juan metro area, where life-threatening rip currents are expected. A moderate risk will continue across other exposed beaches, including western Puerto Rico, Culebra, Vieques, and the U.S. Virgin Islands. Afternoon thunderstorms may also pose a lightning threat to beachgoers, especially across western and northern Puerto Rico, while hot conditions remain a secondary concern. Conditions should improve somewhat Tuesday as the swell gradually subsides.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk from 6 AM AST this morning through late tonight for PRZ001-002-005-008.

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