textproduct: San Juan

KEY MESSAGES

Updated at 208 PM AST Thu Apr 23 2026

* Northerly swell pulses will maintain a high risk of rip currents through at least late tonight, especially along the USVI and PR's north-facing beaches.

* Pulses of northeasterly swells will promote life-threatening rip currents along these beaches from the weekend into early next week. Afternoon convection will maintain a limited flooding risk each day across Puerto Rico, with the risk becoming elevated this weekend and into early next week.

* The region of PR and the USVI will move to a warmer-than- normal period from tomorrow afternoon onward, with heat indices near or above 100F.

Short Term(This evening through Saturday)

Issued at 208 PM AST Thu Apr 23 2026

In general, the US Virgin Islands and Puerto Rico observed little or no rain, with mostly clear skies this morning. However, by noon, cloudiness began to increase across the interior of Puerto Rico and the US Virgin Islands due to local effects. Showers developed across the interior and southwest PR after noon. Maximum temperatures ranged from the mid-80s to the low-90s at coastal sites and from the upper-70s to mid-80s at mountain sites. The winds calm to light and variable under the influence of sea breeze variations.

This afternoon, showers will form later across the interior, spreading to the mountain slopes, where a limited risk of flooding rains remains. Across the U.S. Virgin Islands, generally calm conditions are expected, with some showers downwind from the islands. We cannot rule out showers tonight and overnight as the front approaches from the north-northwest.

Model guidance shows instability increasing from late tonight onward as a mid to upper-level trough approaches the region from the west. The weak steering wind flow will maintain a limited risk of flooding on Friday. Under the aforementioned weather pattern, the chance of strong thunderstorms will increase, especially each afternoon as it moves closer to the region. Some of the limiting factors observed are the dry air at mid levels, which could inhibit widespread activity, even though available moisture will increase at low levels.

By Saturday, a more southeasterly flow will become established, promoting warmer-than-normal temperatures and enhanced diurnal heating. This pattern will support a more active afternoon convection cycle, with showers developing across the interior and drifting northward, with isolated thunderstorms possible. The combination of increasing moisture and stronger heating will also enhance rainfall efficiency, raising the potential for locally heavy rainfall and a slightly elevated risk of excessive rainfall.

Long Term(Sunday through next Wednesday)

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

(18Z TAFS) Issued at 208 PM AST Thu Apr 23 2026

VFR conds will persist across all TAF sites. Aft -SHRA/+SHRA will move across interior PR, resulting in VCSH for JPS through 23/23z. With light winds, -SHRA may move inside TAF site, AMDs will be issue if required. Winds from the E-ENE will weaken and become VRB after 23/23z, strengthening btwn 8 - 12 kt from the E-SE. VCSH may reduce CIGs/VIS over IST and ISX by 24/12z.

MARINE

Issued at 208 PM AST Thu Apr 23 2026

A frontal boundary will linger near or north of the region through late Friday night. This system will promote calm to light flow across the region. At the same time, a pulse of northerly swell will create hazardous marine conditions through this evening. A surface high pressure behind the front will then slowly build from the western to central Atlantic, promoting east-southeast to southerly winds from Saturday into early next week. Pulses of northeasterly swell will arrive around Saturday and another one around Sunday, which will dominate local seas.

BEACH FORECAST

Issued at 208 PM AST Thu Apr 23 2026

Beachgoers, life-threatening rip currents are impacting the north-facing beaches from Rincon to Fajardo, as well as the northern beaches in Culebra, St. Thomas, St. John, and adjacent islands. These conditions will last through at least late tonight. Then, we expect the risk to turn moderate on Friday; however, with the arrival of another northeasterly swell, the risk could jump back to high for north- and east-facing beaches during the weekend. We encourage active monitoring of beach conditions for additional updates.

The risk of rip currents will be low in the south-facing beaches of Puerto Rico and the U.S. Virgin Islands.

In addition, beachgoers should remain alert for afternoon thunderstorms, particularly across western Puerto Rico. These storms may produce gusty winds and frequent lightning.

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 midnight AST tonight for AMZ711-712.

Small Craft Advisory until 6 PM AST this evening for AMZ742.