textproduct: San Juan

KEY MESSAGES

Issued at 1200 PM AST Wed Oct 14 2026

- For the rest of today, expect the afternoon shower and thunderstorm activity to promote localized urban and small stream flooding across southwestern PR. Brief overnight showers will affect the US Virgin Islands and eastern PR.

- Weather conditions will continue to improve through the end of the workweek, reducing the potential for heavy rainfall, flooding, and lightning.

- Heat indices around 102 and 107 degrees Fahrenheit will pose a risk to outdoor workers and vulnerable populations after 10 AM everyday, when mostly clear skies prevail.

- Expect the moderate rip current risk along the northern and eastern-facing beaches of Puerto Rico through the workweek then spread into US Virgin Islands by Saturday, elsewhere a low risk is expected.

Short Term(This afternoon through Friday)

Issued at 1200 PM AST Wed Oct 14 2026

Recent satellite-derived total precipitable water imagery shows moderate tropical moisture across the northeast Caribbean, with values ranging between 1.60 and 1.90 inches. The 14/12z TJSJ upper-air sounding indicated a precipitable water (PWAT) value of 1.78 inches, an unstable boundary layer with mixed-layer CAPE of 1283 J/kg and forecast surface CAPE of 2514 J/kg, alongside a low- level easterly flow around 10 to 15 knots. Although a relatively dry mid-level layer with 47 percent relative humidity and weak convective inhibition was observed, strong diurnal surface heating, local sea breeze convergence, and orographic lifting will erode this cap through the peak heating hours. As a result, scattered to numerous showers and isolated thunderstorms will develop over the interior and track across western Puerto Rico this afternoon. Ensemble guidance highlights localized rainfall accumulations of 1.00 to 2.50 inches across the western portions, which will increase the risk of urban and small-stream flooding. Meanwhile, the U.S. Virgin Islands and portions of eastern Puerto Rico will experience passing trade wind showers and streamers developing downwind of the islands with minor rainfall accumulations.

A similar setup is expected on Thursday as the regional air mass (though drier) retains sufficient low-level moisture, with forecast PWAT between 1.70 and 1.80 inches. Daytime heating along with 925 mb temperatures peaking just below 23C should destabilize the boundary layer by midday. East-to-east-northeast trades will steer developing afternoon convection toward the western interior and southwestern municipalities of Puerto Rico. Ensemble guidance indicates that localized accumulations between 1.00-2.50 inches will once again be possible across these areas. As a result, the flood threat will remain elevated over the SW quadrant of the island. Across the USVI and windward areas of PR, passing showers will remain possible, though significant accumulations are not anticipated.

A pronounced weather transition will occur on Friday as a building mid-to upper-level ridge advects drier air into the northeastern Caribbean. Model guidance and sounding climatology indicate that precipitable water values will plunge to around 1.40 inches, below mid-October normal. At the same time, significant mid-level warming will occur as 500 mb temperatures rise toward -4.0C, approaching two standard deviations above climatology, while mid- level RH between 700-500 mb drops to around 25 percent and 850 mb equivalent potential temperature drops sharply. This intense subsidence and thermal capping will suppress convection, keeping skies mostly sunny to partly cloudy, with only isolated, shallow afternoon convection over western PR producing less rainfall accumulation than previous days.

Long Term(Saturday through next Wednesday)

Issued at 251 AM AST Wed Oct 14 2026

The long-term forecast remains mostly on track, with primarily stable weather conditions expected Saturday through Monday, followed by more active afternoons and slow-moving showers Tuesday and Wednesday.

A mid-to upper-level ridge will maintain dry and stable conditions aloft through Monday. Precipitable water (PWAT) will fluctuate between seasonal and below-seasonal levels, ranging from 1.4 to 1.7 inches. Predominantly easterly steering winds will persist as low-level surface high pressure and a frontal boundary remain north of the local area. Passing cloud patches and trade wind showers will reach eastern sections of the islands (including the U.S. Virgin Islands) from time to time, with no significant impacts. Afternoon showers and isolated thunderstorms remain possible across interior to western Puerto Rico, as well as downwind from El Yunque toward the southern half of the San Juan metropolitan area, and downwind from the USVI, Vieques, and Culebra. A limited flood threat will remain present each afternoon across interior to western Puerto Rico.

More unstable conditions will develop Tuesday and Wednesday as a mid- to upper-level trough approaches from the north, replacing the ridge. This will induce mid-level cooling, dropping 500-millibar temperatures to between -6 and -7 degrees Celsius and steepening mid-level lapse rates. The atmospheric column will moisten under the influence of the trough, yielding seasonal to slightly above- normal precipitable water values. Additionally, steering winds will collapse to around 5 knots and shift southeasterly to southerly as surface low pressure develops north of the region, relaxing the local pressure gradient. This will result in more active afternoons, with scattered to numerous showers and isolated thunderstorms focused mainly across the interior, northwestern, and northern sections of Puerto Rico. An elevated flood threat is expected each afternoon, particularly where persistent shower activity develops. Consequently, urban and small stream flooding is likely, with isolated flash flooding possible.

A limited heat threat remains favored throughout the long-term period. While widespread heat hazards are not anticipated, extremely sensitive individuals could be affected and should take appropriate precautions to protect themselves from heat-related stress.

AVIATION

(18Z TAFS) Issued at 1200 PM AST Wed Oct 14 2026

Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, iso TSRA developing in and around TJPS thru 14/21z may cause tempo MVFR conditions. Mostly VCTS across the rest of the PR terminals this afternoon. Across the USVI terminals, periods of -SHRA due to streamers developing downwind of the islands may cause tempo MVFR conds, particularly at TIST thru 14/20z. For the overnight hours, mostly VCSH expected at TJSJ and the USVI terminals due to passing trade wind showers. The 14/12z TJSJ sounding indicated E-ENE winds up to 19 kt blo FL150.

MARINE

Issued at 1200 PM AST Wed Oct 14 2026

Relative tranquil seas should prevail through at least Thursday, followed by a small, but long period northeasterly swell that will gradually reach the offshore and coastal Atlantic waters by late Friday into Saturday morning. However, afternoon thunderstorms remain possible across the western waters of PR each day. Mariners should remain alert for sudden wind gusts, locally higher seas, and reduced visibility near thunderstorms.

BEACH FORECAST

Issued at 1200 PM AST Wed Oct 14 2026

A moderate risk of rip currents will persist along north and east- facing beaches of Puerto Rico, including Culebra, through Friday, with a low risk elsewhere. The risk may expand to additional beaches, including portions of the U.S. Virgin Islands, over the weekend as northeasterly long period swell reaches the area and build seas. Afternoon thunderstorms will pose a lightning threat to beachgoers, particularly along western Puerto Rico, although this threat should gradually decrease through late week. Meanwhile, a limited extreme heat risk will persist each day, with locally higher heat stress possible during the late morning and afternoon hours.

SJU WATCHES/WARNINGS/ADVISORIES

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