textproduct: San Juan

KEY MESSAGES

Updated at 255 AM AST Thu Apr 23 2026

* Northerly swell pulses will bring a high risk of rip currents today, especially along north-facing beaches. Risk lowers to moderate thereafter.

* A limited flooding risk persists daily, becoming elevated this weekend into early next week. Isolated thunderstorms possible Saturday.

* Warmer-than-normal conditions develop this weekend, with heat indices near or above 100F.

* For the U.S. Virgin Islands, rip currents remain the main hazard, with a high risk today decreasing to moderate, while heat increases late in the period.

Short Term(Today through Saturday)

Issued at 255 AM AST Thu Apr 23 2026

A relatively tranquil overnight period prevailed, with mostly clear skies and little to no shower activity over land. This pattern will persist into the morning hours as a drier air mass remains in place, with below-normal precipitable water values early in the day. Some moisture will gradually increase across western Puerto Rico, while drier conditions linger over eastern areas, Vieques, Culebra, and the U.S. Virgin Islands. Mid-level dry air and a persistent inversion will limit vertical development. Despite these somewhat hostile conditions, convection is still expected, driven by daytime heating, with scattered to locally numerous showers at times developing over the interior and drifting toward nearby coastal areas during the afternoon. Activity should remain brief and localized.

Moisture will continue to increase into the end of the workweek, although it will remain mostly shallow in nature. Conditions will stay fairly similar at first, and any convection that develops will tend to drift north to northwestward on Friday with the prevailing flow. By Saturday, a more southeasterly flow becomes established, supporting warmer-than-normal conditions along with stronger daytime heating. This evolving pattern will favor a more active afternoon convection cycle, with showers developing over the interior and shifting northward, with an isolated thunderstorm possible.

The overall steering flow will remain weak through the period, favoring slow-moving showers and localized flooding driven by persistent rainfall over the same areas. This risk will remain limited through Friday. By Saturday, increased moisture combined with stronger heating and warmer-than-normal conditions will support more efficient and heavier rainfall, leading to a slightly elevated risk of excessive rainfall.

Long Term(Sunday through Thursday)

Issued at 255 AM AST Thu Apr 23 2026

No significant changes have been introduced to the long-term period, and the inherited forecast remains on track. A surface high-pressure system over the central Atlantic will begin to migrate toward the eastern Atlantic on Sunday, promoting a southerly wind flow through Monday. Winds will veer from the south-southeast as the surface high strengthens over the central-eastern Atlantic. By Sunday, a mid- level ridge will bring drier, stable air, inhibiting the development of strong showers and keeping precipitable water (PWAT) values near 1.25 inches(below seasonal averages).

An increase in moisture is anticipated from Monday into Tuesday, with PWAT values rising to between 1.50 and 1.80 inches as a deeper plume of moisture from the Caribbean arrives. The environment will become increasingly unstable due to this moisture influx alongside an upper-level trough, leading to more widespread shower and thunderstorm activity across Puerto Rico and the U.S. Virgin Islands. While passing showers are expected to move into the islands, the most active rainfall is expected over the interior and the western to northwestern portions of Puerto Rico during the afternoon hours. Although 500 mb temperatures will remain within seasonal values of -6 to -8C, isolated thunderstorms cannot be ruled out each afternoon.

As this southerly flow prevails into next week, 925 mb temperatures will increase to well above climatological values. Surface highs are expected to range from the upper 80s to low 90s along coastal and urban areas, and from the low to mid-80s across higher elevations. Heat indices will climb as well, likely surpassing 100F from Sunday into mid-week as the combination of southerly winds and abundant moisture peaks during the daytime hours. To stay safe during this period of high heat and humidity, residents and visitors are strongly encouraged to prioritize hydration by drinking plenty of water and avoiding prolonged exposure to the sun.

AVIATION

(06Z TAFS) Issued at 255 AM AST Thu Apr 23 2026

VFR conds will prevail at all TAF sites thru the fcst pd, with brief MVFR possible at JPS btw 23/1622Z in VCSH. VCSH also possible ovrngt at TISX. Winds will be lgt/vrb this mrng, bcmg ENE 812 kt with gusts up to 20 kt and sea breeze variations this aftn, then returning to lgt/vrb ovrngt.

MARINE

Issued at 255 AM AST Thu Apr 23 2026

A frontal boundary lingering just north of the region is supporting light to gentle northeasterly winds, while pulses of a long-period northerly swell continue to spread across the Atlantic waters, resulting in hazardous seas for small craft, particularly offshore. This swell will gradually subside late in the week. As the boundary weakens, surface high pressure drifting southeastward will promote a gradual strengthening of winds, becoming moderate from the south over the weekend. Another northerly swell is expected early next week. In addition, remnant moisture from the frontal boundary may enhance shower activity over the waters, with convection capable of producing locally hazardous conditions.

BEACH FORECAST

Issued at 255 AM AST Thu Apr 23 2026

A high risk of rip currents is present along north to north- northeast facing beaches of Puerto Rico, Culebra, and the northern U.S. Virgin Islands as pulses of a long-period northerly swell spread across the local waters, where life-threatening rip currents are likely. Conditions will gradually improve, with the risk decreasing by Friday, transitioning to moderate risk across exposed areas, where rip currents remain possible, while low risk persists along Caribbean-facing beaches. Another northerly swell this weekend into early next week will bring a renewed increase in rip current risk.

SJU WATCHES/WARNINGS/ADVISORIES

PR...High Rip Current Risk from 6 AM AST this morning through late tonight for PRZ001-002-005-008-010-012.

VI...High Rip Current Risk from 6 AM AST this morning through late tonight for VIZ001.

AM...Small Craft Advisory until midnight AST tonight for AMZ711-712.