textproduct: San Juan

KEY MESSAGES

Issued at 240 PM AST Tue Mar 17 2026

* Hazardous marine and coastal conditions will persist through much of the week. Small Craft Advisories remain in effect for several local waters, and a high risk of rip currents is expected for many beaches of Puerto Rico and the U.S. Virgin Islands.

* Breezy to windy easterlies will continue through at least Wednesday night.

* Passing showers will increase across the U.S. Virgin Islands and eastern PR late this afternoon into the evening.

* A frontal boundary and associated trough will increase shower activity from late this week into the weekend, bringing periods of unsettled weather across Puerto Rico and the U.S. Virgin Islands.

Short Term(This evening through Thursday)

Issued at 240 PM AST Tue Mar 17 2026

Once again, this morning, we had variable conditions from mostly sunny skies across the PR's western half and St Croix to partly sunny and partly cloudy skies across portions of the eastern half of PR, and the US Virgin Islands. A strong surface high-pressure system promoted windy conditions across the islands, with weather stations reporting sustained winds of 15 to 25 mph, gusting to 25 to 35 mph or higher. Maximum temperatures ranged from the mid- to upper 80s along the coast to the lower 80s across the mountains.

This afternoon, breezy to windy conditions will continue, with gusts reaching up to 35 mph. Under this wind pattern, brief periods of moderate to heavy rain will primarily affect the U.S. Virgin Islands and the windward areas of Puerto Rico, leading to occasional periods of moderate to locally heavy rain. However, expect periods of sunshine and mostly clear skies overnight. Limited showers may reach western Puerto Rico, but most rainfall is anticipated in the windward areas. By this evening, moisture levels will increase again with the arrival of a weak perturbation, bringing showery weather to some windward areas. Additionally, winds will gradually ease late tonight through early Wednesday morning, decreasing to around 15 to 20 knots as the local pressure gradient relaxes.

By Thursday, the pattern will begin to shift toward a more unstable, wetter pattern, with moisture rising into the mid levels of the atmosphere over the islands. Meanwhile, trade winds will continue to weaken, with 925 mb winds decreasing to around 1017 knots. The combination of lighter steering flow and increasing moisture should support a more typical shower pattern across the region and stronger afternoon convection.

LONG TERM

Issued at 258 AM AST Tue Mar 17 2026

Variable conditions are expected in the long-term forecast. A broad surface high pressure over the Central Atlantic will promote winds with a southerly component, with patches of moisture across the CWA on Friday. This will bring passing showers over windward sections in the morning, with afternoon showers over north/northwestern Puerto Rico. Rainfall accumulations should remain limited, leading to ponding of water over roadways and poorly drained areas.

Weather conditions will likely become wetter and more unstable in the upcoming weekend, as a deep-layered trough with an associated frontal boundary will likely approach the region by Saturday, inducing a pre-frontal trough that will likely increase shower and thunderstorm activity. Additionally, a col region will move across the region by Saturday, with 925 mb winds plummeting to well below normal (mostly variable and calm winds). According to the latest model guidance, Precipitable Water values are expected to range between 1.5 and 1.75 inches, which is above the climatological normal, with the best moisture content in the low and mid levels (above 70%), increasing chances of scattered to numerous showers. Additionally, weakening winds will result in stationary showers and thunderstorms, with the highest potential of flooding on Saturday and Sunday.

Due to the approach of the trough, the mid-level temperatures should slightly cool (around -8 degrees Celsius), with a jet streak positioning over the region, allowing ventilation aloft (between 70 and 90 kt). Although the best of convection should remain north of the CWA, conditions will likely be favorable for deeper convection and increasing lightning potential. Therefore, the most likely scenario is an advective pattern on both Saturday and Sunday, with afternoon convection over the mountain ranges of Puerto Rico. Rainfall accumulations will likely result in urban and small streams flooding, with a low chance of flash flooding, over the aforementioned areas.

By Monday, another surface high pressure exiting eastern CONUS will increase pressure gradient, promoting E- ENE winds. Weather conditions should gradually improve; however, remaining moisture content should be enough for the development of showers across the regional waters into windward sections throughout the day, along with afternoon convection. Residents and visitors are encouraged to continue to monitor the weather forecast due to discrepancies between global solutions.

Although Friday will likely be the warmest day of the long-term, maximum temperatures should remain in the mid to high 80s, with localized low 90s, across low elevation areas of the islands, with no heat threat expected.

AVIATION

(18Z TAFS) Issued at 240 PM AST Tue Mar 17 2026

Mainly VFR conditions will prevail under E to ESE flow at 15 to 25 kts with higher gusts at 27 to around 30 kts. By 17/20Z -SHRA/VCSH will be steered towards the USVI terminals, and shortly after the eastern PR terminals. This can lead to brief MVFR cigs and mostly VCSH/-RA periods. Winds decreasing somewhat after 17/23Z, especially for PR terminals, increasing again after 18/13Z.

MARINE

Issued at 240 PM AST Tue Mar 17 2026

Strong high pressure over the central Atlantic will maintain fresh to strong easterly winds and choppy to rough seas across the northeastern Caribbean waters. A weak easterly perturbation will increase passing showers tonight. By late week, a frontal boundary moving eastward across the western Atlantic will weaken the local pressure gradient, allowing winds to gradually diminish while a pre-frontal trough near Hispaniola increases moisture and promotes more unsettled conditions from late Thursday into the weekend.

BEACH FORECAST

Issued at 240 PM AST Tue Mar 17 2026

Beach conditions will remain hazardous for inexperienced swimmers across much of the local islands. Breezy to windy easterly winds will continue to generate choppy to rough seas across the regional waters, increasing wave action along exposed beaches. As a result, a high risk of rip currents will persist along many exposed beaches in PR and the USVI through much of the week.

Beachgoers should exercise caution, remain aware of changing coastal conditions, and monitor the latest forecasts and statements. For additional information, visit: weather.gov/beach/sju

FIRE WEATHER

Issued at 240 PM AST Tue Mar 17 2026

A Fire Danger Statement (RFDSJU) remains in effect for the coastal plains of southern Puerto Rico. The KeetchByram Drought Index (KBDI) remains elevated, with values around 687 in Cabo Rojo and 552 in Gunica, indicating increasingly dry fuels.

East to east-southeast winds of 15 to 22 mph, with gusts up to 30 mph, will continue the rest of the day. Although a few showers cannot be ruled out, RH values will continue around 4555 percent across the southern coastal plains.

The aforementioned dry fuels, gusty winds, and lower relative humidity are supporting elevated fire weather conditions across southern Puerto Rico today.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk through Wednesday afternoon for PRZ001>003- 005-007-008-011>013.

VI...High Rip Current Risk through Wednesday afternoon for VIZ001-002.

AM...Small Craft Advisory until 6 PM AST Wednesday for AMZ711-712-716- 723-726-733-735-741.