Area Forecast Discussion

KEY MESSAGES

Issued at 100 PM AST Fri Oct 30 2026

* Showers and thunderstorms will continue to affect the interior and western Puerto Rico. There is a risk for urban and small stream flooding and frequent lightning. * Increased showers and thunderstorms by late Saturday and Sunday, confidence has increased.

* Hot conditions will persist across the islands, with a level of heat that mainly affects those individuals that are extremely sensitive, outdoors and without adequate hydration through tomorrow.

Short Term(This evening through Sunday)

Issued at 100 PM AST Fri Oct 30 2026

Surface high pressure anchored over the western and central Atlantic will maintain a gentle to moderate east-to-southeasterly trade wind flow across the local islands through the first half of the weekend. Moisture will remain near seasonal climatological values, with precipitable water values ranging between 1.70 and 1.80 inches. Despite a somewhat dry mid-level layer, intense daytime heating combined with warm boundary layer temperatures near 21C to 22.5C, will promote strong sea-breeze convergence and afternoon convective development. This diurnal pattern will focus primarily over the interior and western sectors of Puerto Rico, where slow moving showers could produce localized rainfall totals of 1 to 2 inches and cause urban and small stream flooding. Before afternoon cloud cover and precipitation begin, the combination of high surface dewpoints and the elevated low-level thermal profile will produce heat indices between 102F and 108F across some urban and lower elevation coastal communities in north-central and western PR. Winds will turn more east-to-northeast by Saturday afternoon as the surface high continues to build over the western Atlantic, shifting the focus of afternoon convection toward the Cordillera and west/southwest PR, while streamers develop downwind of the USVI.

A notable shift to a wetter, more unsettled pattern will begin late Saturday night and continue into Sunday as tropical moisture surges into the region from the east. Latest global model guidance highlights precipitable water values climbing above 2.00 inches, well above normal values for early November. Mid-level moisture will increase, with 700-500 mb relative humidity forecast to exceed 70 to 80 percent, effectively eliminating the convective inhibition present earlier in the weekend. Aloft, 200 mb flow will become predominantly southwesterly, providing modest ventilation and upper- level divergence over the eastern Caribbean basin. This favorable environment will support heavy shower and thunderstorm development across PR and the USVI. As a result, the risk of urban and small stream flooding will broaden considerably on Sunday, with isolated flash flooding and minor mudslides becoming a distinct possibility over steep terrain.

Long Term(Monday through next Thursday)

Issued at 100 PM AST Fri Oct 30 2026

The forecast remains on track with a wet and humid pattern expected through the long-term period. Abundant moisture will promote unsettled weather and the potential for shower activity. Precipitable water values will remain above normal for this time of year, sitting at the 75th percentile for November and ranging between 2.00 and 2.40 inches through much of the period.

At the surface, a high-pressure system migrating from the U.S. East Coast into the central Atlantic will maintain an easterly to southeasterly wind flow. By Wednesday, winds will gradually shift to the south-southeast. Late Wednesday into Thursday, an upper-level trough to the west of the islands will cause the local pressure gradient to relax, resulting in a weak, southerly wind flow.

From Tuesday onward, guidance indicates a gradual warming of mid- level temperatures at 500 mb, which should limit the development of thunderstorms across the region. However, as winds become light by midweek, any developing showers will be slow-moving. This will increase the risk of localized flooding, particularly across portions of central and northern Puerto Rico during the afternoon hours. Confidence in the overall rainfall coverage and intensity remains uncertain, as upper-level dynamics may become less favorable and afternoon convection will heavily depend on lingering cloud cover and the amount of daytime heating. Overall, a typical diurnal weather pattern is expected. Passing showers will move across the U.S. Virgin Islands and eastern to southeastern Puerto Rico during the overnight and morning hours. During the afternoons, convection will develop across the interior, western, and northern portions of Puerto Rico, with localized showers and streamers developing downwind of El Yunque and the local islands on most days. Periods of heavy rainfall could lead to urban and small stream flooding and quick river rises.

At the 925 mb level, temperatures will remain above normal through most of the period. The warmest days are expected by midweek, as the southeasterly to southerly winds brings in deeper moisture. This combination will result in warm conditions and elevated heat indices across the region. Residents and visitors are encouraged to stay hydrated and continue monitoring the forecast for updates as model guidance becomes more consistent.

AVIATION

(18Z TAFS) Issued at 100 PM AST Fri Oct 30 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, tempo MVFR conds are possible thru 30/22z at TJBQ/TJSJ due to locally induced SHRA/TSRA. Across the rest of the area terminals, mostly VCSH expected. The 30/12z TJSJ sounding indicated ESE winds up to 17 kt blo FL080. Light and variable winds expected overnight, increasing ENE at 10-15 kt aft 31/13z.

MARINE

Issued at 100 PM AST Fri Oct 30 2026

The surface high pressure over the central Atlantic and a low will keep promoting moderate east to southeasterly winds across the regional waters during the weekend. Nearshore buoys shows seas around 1 to 3 feet and offshore buoys around 4 feet, meaning that seas are subsiding and starting to return normal sea levels. Expect choppy conditions at times across portions of the offshore waters and local passage reducing visibility and generating gusty winds.

BEACH FORECAST

Issued at 100 PM AST Fri Oct 30 2026

During the weekend, expect moderate risk of rip currents along the northern beaches of Puerto Rico and Culebra, as well as the US Virgin Islands. This means life-threatening rip currents are possible in the surf zone. Beachgoers should remain cautious. Expect periods of afternoon showers and thunderstorms today into the weekend. If you hear thunder, seek shelter immediately inside a sturdy building.

SJU WATCHES / WARNINGS / ADVISORIES

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