textproduct: San Juan

KEY MESSAGES

Issued at 1205 PM AST Fri May 22 2026

* At least through the Holiday weekend: morning passing showers are expected across the windward areas of Puerto Rico and the U.S. Virgin Islands, followed by afternoon thunderstorms across central and western Puerto Rico.

* A moderate risk of life-threatening rip currents will persist across all northern, eastern and southern beaches of the islands.

* Breezy conditions will result in choppy seas through early next week.

Short Term(This afternoon through Sunday)

Issued at 1205 PM AST Fri May 22 2026

Current satellite-derived Total Precipitable Water (TPW) imagery shows an expansive plume of moderate tropical moisture filtering west-northwestward into the eastern Caribbean. According to the latest GFS run, precipitable water values will fluctuate between 1.75 and 2.00 inches through Saturday, then increase to near 2.15 inches by Sunday. Mid-level and low-level relative humidity are expected to spike well above the 75th percentile on Saturday, peaking near 80-90% in the 700-500 mb layer. This setup will interact with daytime heating, local effects, and brisk easterly winds driven by a strong surface high pressure in the central Atlantic, producing afternoon showers and thunderstorms each day.

Consequently, high-resolution NBM and ECMWF ensemble guidance agree on a significantly wetter pattern developing over the weekend. For today, expect a relatively standard diurnal convective pattern with scattered showers and afternoon thunderstorms over western/interior Puerto Rico with periods of locally heavy rainfall, and across the USVI and eastern PR, generally light to moderate localized accumulations (0.25 to 0.75 inches). However, as deeper moisture arrives on Saturday, shower and thunderstorm coverage will increase substantially. By Sunday, aided by the increasing PWAT values and deep-layer saturation, widespread showers and isolated to scattered thunderstorms are anticipated across the islands. Guidance suggests daily rainfall accumulations of 1 to 2 inches, with localized maximums potentially exceeding 3 inches along the eastern half and western Puerto Rico. Given the expected saturated profile, increasing rainfall rates, and consecutive days of precipitation, the threat of urban, small stream, and localized flash flooding will be elevated through Sunday afternoon.

Long Term(Monday through next Friday)

Issued at 148 AM AST Fri May 22 2026

Variable conditions are still expected in the long-term forecast, with Tuesday and Wednesday being the most unstable. A broad surface high pressure over the western Atlantic is expected to extend into the Central Atlantic, with winds shifting from the E-SE through most of the period. Strengthening winds will bring breezy conditions throughout the long-term forecast, with Monday the windiest day. Although a mid-level ridge is expected to build over the Western Atlantic, troughiness associated with an upper-level trough will maintain slight instability across the CWA. The latest model guidance solutions continue to suggest an increase in moisture content in the region, with the latest solution showing PWAT values near to above normal (between 1.8 and 2.0 inches, with a low chance of reaching 2.2 inches). Additionally, low to mid-level moisture should ascend to well above climatological normal (60 - 80%), with model soundings suggesting skinny profiles. In terms of instability, deep convection is expected across the region, particularly during the afternoons and evenings, as mid-level temperatures should remain cool (between -7 and -8 degrees Celsius), while guidance shows signals of enhanced vorticity on Tuesday and Wednesday. These conditions combined with local effect and daytime heating should allow deeper convection activity. For each day, expect passing showers moving over windward sections of the islands throughout the day, with afternoon convection over interior and western to northwestern Puerto Rico. Additionally, island streamers could move over eastern Puerto Rico, including the San Juan Metro Area, increasing flooding potential. Due to fast-moving showers, rainfall accumulations should remain limited, resulting in ponding of water across roadways and poorly drained areas and minor flooding over the aforementioned areas. However, urban and small stream over localized areas cannot be ruled out. In addition to flooding, hazards such as gusty winds and lightning can be expected during periods of heavy showers. Weather conditions should gradually improve by the end of the period.

In terms of heat, model guidance continues to suggest temperatures typical for this time of the year. However, combined with available moisture, localized urban and coastal areas of the islands may experience heat indices reaching 100 degrees Fahrenheit. Although the risk will remain limited, individuals sensitive to heat should take the necessary precautions.

AVIATION

(12Z TAFS) Issued at 1205 PM AST Fri May 22 2026

Mainly VFR conditions expected. However, SHRA/TSRA will develop across the interior and NW PR, and downwind from El Yunque possibly resulting in brief MVFR conds at TJBQ/TJSJ thru 21z. The 22/12z TJSJ sounding indicated ESE winds up to 22 kt blo FL060. Sfc winds will prevail from the east overnight at 8-12 kt. Passing SHRA en route fm the Leeward terminals should cause mostly VCSH across the USVI terminals.

MARINE

Issued at 1205 PM AST Fri May 22 2026

Moderate to fresh easterly winds will continue across the regional waters through next week due to a strong surface high pressure over the central Atlantic. Choppy seas up to 6 feet will persist across the offshore water and passages, and small craft should exercise caution. Stronger winds and rough seas are expected by Monday, and Small Craft Advisory conditions are possible across the offshore Atlantic waters on Monday and Tuesday. Isolated afternoon thunderstorms are expected to develop near the western coastal waters of Puerto Rico, producing locally higher winds and seas each day.

BEACH FORECAST

Issued at 1205 PM AST Fri May 22 2026

A moderate risk of rip currents will persist across most local beaches through the next several days due to persistent breezy conditions and wind-driven seas. The highest risk will continue along north, east, and south facing beaches of all the islands. A moderate risk of rip currents means that life-threatening rip currents are possible in the surf zone.

SJU WATCHES/WARNINGS/ADVISORIES

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