textproduct: San Juan

KEY MESSAGES

Issued at 200 PM AST Thu Jun 11 2026

* Showers and thunderstorms are expected this afternoon across the interior and western portions of PR as a weak tropical wave moves through the region. A limited to elevated flood risk is expected.

* Hot heat index values will prevail from Friday onward, especially across urban, coastal, and lower-elevation areas.

* Saharan dust particles will produce hazy skies, particularly from tonight through Friday night. Trace concentrations are expected to persist through the weekend.

* A moderate risk of life-threatening rip currents will return Friday night along the north and east-facing beaches of PR and the USVI, expanding to southern PR from Sunday into early next week as winds strengthen.

Short Term(This evening through Saturday)

Issued at 200 PM AST Thu Jun 11 2026

During the morning hours, showers associated with the approaching tropical wave and a weak shearline linked to a surface low north- northeast of the forecast area remained mostly over the regional waters. A few localized showers affected the waters near St. Thomas and St. John early in the period, while by late morning isolated thunderstorms developed west of St. Thomas and north of Culebra. However, most of this activity stayed offshore, and conditions across the islands were generally tranquil through the morning hours with a few showers moving over the islands.

The axis of the tropical wave is currently south of Puerto Rico, but the wave has remained rather weak and is embedded within suspended Saharan dust. Nevertheless, precipitable water values remain near to slightly above normal, and the combination of available moisture, favorable dynamics associated with the tropical wave, a mid- to upper-level trough, surface heating, and local sea breeze convergence will continue to support afternoon shower and thunderstorm development. The highest rainfall potential remains across the interior into western and northwestern Puerto Rico, where urban and small-stream flooding will remain possible with the strongest activity. Isolated flash flooding cannot be ruled out in the most vulnerable areas. That said, some mid-level dry air intrusion may limit coverage and intensity, causing convection to become more localized than previously anticipated.

Although favorable upper-level dynamics will persist through the short-term period, including cold air advection near 500 mb and steepening 700-500 mb lapse rates, slightly higher concentrations of suspended Saharan dust behind the current wave should promote a more stable low-level environment on Friday. As a result, shower and thunderstorm activity is expected to be hindered for the most part. Still, lingering patches of moisture, local effects, and daytime heating may support isolated to locally scattered afternoon convection, mainly across interior and western Puerto Rico.

By Friday evening into Saturday, a drier air mass will continue to filter into the region, with moisture content falling to nearly two standard deviations below normal. This will make Saturday the least active day of the short-term forecast period. A more typical trade wind pattern is expected, with brief passing showers possible across windward areas during the morning hours, followed by limited and localized afternoon convection across western Puerto Rico. Suspended Saharan dust will likely continue to promote hazy skies at times. Temperatures will remain above normal, and heat indices may once again reach advisory criteria, mostly across coastal and urban areas.

Long Term(Sunday through Thursday)

Issued at 128 AM AST Thu Jun 11 2026

Confidence is increasing in global models for the long-term forecast, with mainly a typical and stable weather pattern. Wind pattern should be dominated by a surface high pressure, lingering in the western Atlantic, producing E-ESE winds that will likely result in breezy conditions across the islands. The model guidance suggests patches of moisture moving from time to time, as PWAT values may fluctuate between 1.3 and 1.6 inches, though the 700 - 500 mb moisture content may plummet, ranging between 10 and 30%. In terms of instability, a ridge should approach the local area and linger nearby through most of the forecast period, warming 500 mb temperatures (between -6 and -7 degrees Celsius), allowing sinking air and stability aloft. Additionally, the Galvez-Davison Index (GDI) suggests at most shallow convection in the afternoon over western portions of Puerto Rico, with thunderstorms, if any, becoming isolated and brief. Each day, windward sections may receive isolated showers in the morning, while the combination of local effects, daytime heating, and available moisture should bring shallow convection across western Puerto Rico. Additionally, with the winds keeping up, island streamers will likely develop, moving into portions of eastern Puerto Rico, including the San Juan Metropolitan Area. Due to the current soil conditions, low streamflows, and QPF remaining below one inch, the flooding threat will remain low throughout the forecast period.

Although the latest model guidance suggests 925 mb temperatures typical for this time of the year, this, combined with the available moisture will increase the chance of heat indices reaching and exceeding 100 degrees Fahrenheit. Hence, the heat threat will remain limited through most of the long-term, increasing on Tuesday due to a slight increase in moisture content in the 1000-850 mb layer.

AVIATION

(18Z TAFS) Issued at 200 PM AST Thu Jun 11 2026

Mainly VFR conds expected across all terminals thru the next 24 hrs. However, locally induced SHRA/TSRA expected to develop across interior and NW PR btw thru 22Z, resulting mainly in VCTS at TJBQ. Elsewhere, VCSH expected at times. HZ due to Saharan dust will persist through the period, particularly aft 12/10Z with brief periods of reduced VIS possible. E-ESE winds will increase to 13-16 kt, with hir gusts and sea breeze variations aft 11/13Z.

MARINE

Issued at 200 PM AST Thu Jun 11 2026

An induced surface trough interacting with a weak tropical wave will provide a better chance for thunderstorm development today. Gentle to moderate east to east-southeast winds and seas of 2 to 4 feet will prevail across the regional waters through at least Friday night. As a high pressure gradually strengthens over the Atlantic beginning Saturday, it will support fresh trade winds and moderate seas into early next week. Expect seas to build to 4 to 6 feet, occasionally higher, across the regional waters and local Caribbean passages. Small craft operators will likely need to exercise caution during that period.

BEACH FORECAST

Issued at 200 PM AST Thu Jun 11 2026

The rest of this afternoon and into tonight, there is a low risk of rip currents across all beaches of Puerto Rico and the U.S. Virgin Islands. However, beachgoers should still exercise caution, as life-threatening rip currents can occur even when the risk is low, especially near groins, jetties, reefs, and piers.

Similar conditions are expected to prevail during the day on Friday. However, beginning Friday night and continuing through Saturday night, winds will gradually increase, resulting in a moderate risk of rip currents along the northern and eastern exposed beaches of Puerto Rico, as well as across Culebra, Vieques, and the U.S. Virgin Islands. A moderate risk means that life-threatening rip currents are possible in the surf zone, and beachgoers should exercise caution.

From Sunday into early next week, winds are expected to strengthen further, and the moderate risk of rip currents will expand to include the southern beaches of Puerto Rico.

FIRE WEATHER

Issued at 200 PM AST Thu Jun 11 2026

Expect a low fire weather risk across the southern sections of the islands through at least Friday. However, by Saturday, a dry air mass is expected to move over the forecast area, potentially lowering relative humidity values to near or below critical thresholds across the southern coastal plains, and possibly extending into other areas.

Additionally, breezy conditions are expected to return on Saturday. Combined with above-critical KBDI values and increasingly dry fuels, this could lead to elevated fire danger conditions. Therefore, conditions may become favorable for the spread of wildfires along the southern coastal plains of Puerto Rico on Saturday, and a Fire Danger Statement (RFDSJU) may be necessary.

SJU WATCHES/WARNINGS/ADVISORIES

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