textproduct: San Juan

KEY MESSAGES

Issued at 324 AM AST Wed Jun 24 2026

* The moisture field from a weak tropical wave moving across the region will enhance the potential for showers today as well as for afternoon showers and t-storms mainly across interior to W-NW PR. * The day will start with moderate concentrations of Saharan Dust. High concentrations of Saharan Dust will then reach the USVI this afternoon, continue moving westward over PR this evening and persist over the islands through Friday. This will result in hazy skies, reduced visibility and deteriorated air quality.

* Breezy to locally windy ESE winds will result in up to a moderate risk of rip currents across most coastal areas today as well as in choppy seas and Small Craft Exercise Caution conditions.

* Up to an elevated heat risk will persist during the next several days.

* An upper-level low will induce a surface trough that is forecast to cross the region on Saturday, promoting lighter winds as well as a limited flooding and lightning risk.

Short Term(Today through Friday)

Issued at 324 AM AST Wed Jun 24 2026

A surface high pressure over the Atlantic will continue to result in breezy, to locally windy, ESE winds throughout the rest of the workweek. 925 mb wind speeds are forecast to continue above normal values for this time of the year, decreasing to more normal values on Friday. Precipitable water (PWAT) should fluctuate from below normal to normal values during the forecast period, peaking today (around 1.9 inches) as a tropical wave moves south of the islands and its moisture field moves over the region. This tropical wave will also be embedded in Saharan Dust concentrations. Although the bulk of the moisture from this wave will stay over the Caribbean waters, cloudiness and showers can still be steered towards the islands under the ESE flow before the onset of high concentrations of Saharan Dust later this afternoon. PWAT values will gradually decrease to more borderline below-normal to low end normal values (around 1.5 to 1.6 inches) Thursday and Friday as patches of moisture continue to be steered towards the islands. In the mid to upper levels, mid-level ridging will continue, mainly on Thursday and Friday, along with warm 500 mb temperatures. This, along with the Saharan Dust will serve to limit shower and t-storm activity, especially tomorrow, Thursday. An upper lows will stay well northeast and north of the region during the period. Trade wind showers will continue to reach windward sectors from time to time, especially during the overnight and morning hours, being somewhat enhanced by the moisture field from the tropical wave. Today and possibly Friday, afternoon showers and isolated t-storms will affect mainly interior to W and NW Puerto Rico today as diurnal heating and local effects develop; lines of showers can also develop downwind of El Yunque and the local islands. This activity is forecast to be limited, if any, on Thursday due to high Saharan Dust concentrations. An elevated heat risk will persist during the period, with heat indices surpassing 108 degrees Fahrenheit. 925 mb temperatures today suggest normal to above normal temperatures under E to ESE flow. Heat Advisories can be issued later today and/or during the short term period as highs over urban areas and lower elevations reach the upper 80s to low 90s.

Saharan Dust concentrations will continue gradually increasing today. The leading edge of a Saharan Air Layer (SAL) will increase concentrations to moderate early today as it arrives along with the tropical wave, resulting in hazy skies. Air quality and visibility are projected to further deteriorate as current model guidance suggests that high concentrations of Saharan Dust will reach the USVI this afternoon and spread towards PR during the afternoon and evening, these high concentrations will then persist through Friday, gradually becoming more moderate Friday afternoon afterwards. This will result in hazy skies, reduced visibility and deteriorated air quality. Sensitive groups should follow medical recommendations, particularly Wednesday afternoon through Friday.

Long Term(Saturday through Wednesday)

Issued at 324 AM AST Wed Jun 24 2026

At the beginning of the long-term period, an upper-level low will induce a surface trough that is expected to cross the region on Saturday. This feature will cause the surface high pressure over the central Atlantic to weaken, reducing the local pressure gradient and resulting in lighter winds that will gradually back to the northeast. Moisture content will increase to near-normal levels, with precipitable water values ranging from 1.60 to 1.75 inches, and locally higher amounts possible. In addition, Saharan dust concentrations will decrease as the dust plume moves away from the area, leading to improved air quality conditions. As a result, passing showers are expected across windward areas and the vicinity of the USVI during the early morning hours, followed by showers and isolated thunderstorms over the western sectors of Puerto Rico during the afternoon due to the combination of local effects and daytime heating. Temperatures at 500 mb are expected to remain above normal, around -5 C to -6 degrees C, but may still be sufficient to support a few lightning strikes.

On Sunday, drier conditions, with below-normal precipitable water values, and low concentrations of Saharan dust will begin to arrive, accompanied by a southeast wind flow. The primary hazard on this day will be warm to hot conditions, as indicated by forecast guidance showing 925 mb temperatures around two standard deviations above normal. Daytime highs are expected to reach the upper 80s to low 90s, and heat indices may exceed 100 degrees F, particularly across coastal and urban areas. An elevated heat risk will likely persist.

Early next week through mid-week, current guidance suggests that a tropical wave may approach the Caribbean Basin and increase low- level moisture across the local islands. Precipitable water values are forecast to increase to near-normal or slightly above-normal levels based on climatological data. This would likely enhance rainfall chances, leading to a greater frequency of showers and afternoon convection. At the same time, cooler temperatures aloft associated with lower 500 mb temperatures may provide additional support for convective development. However, Saharan dust is also expected to be present, and its interaction with the incoming moisture remains uncertain. Continue to monitor the forecast as updates become available.

AVIATION

(06Z TAFS) Issued at 324 AM AST Wed Jun 24 2026

A tropical wave will move south of the region today, with its moisture field reaching the area and providing some relief in terms of RH values. Nevertheless, over southern of PR, relative humidities in the low 50s continue to be possible. Winds will be from the east- southeast at 10 to 20 mph, with gusts up to 33 mph, especially from mid morning into the afternoon. Although a moderate fire danger risk is forecast, a Fire Danger Statement could be issued later today if the moisture field from the tropical wave moves further south, giving way to a high fire danger risk. An elevated heat risk will also persist over the area and Saharan Dust concentrations will gradually increase as the day continues.

MARINE

Issued at 324 AM AST Wed Jun 24 2026

A broad high pressure system over the central Atlantic will maintain moderate to fresh easterly winds across the regional waters through the next several days. Choppy seas and Small Craft Exercise Caution conditions are expected across most local waters, with seas generally between 4 and 6 feet and occasionally up to 8 feet offshore and in local passages. Moderate Saharan dust will persist across the region, increasing Wednesday through Friday and leading to periods of reduced visibility.

BEACH FORECAST

Issued at 324 AM AST Wed Jun 24 2026

A moderate risk of rip currents will persist across most north-, east-, and south-facing beaches of Puerto Rico and the U.S. Virgin Islands through the end of the workweek. Beachgoers should exercise caution, especially near jetties, piers, reefs, and other areas known for stronger currents. Rip current conditions are expected to gradually improve by Friday night, with a low risk forecast across most local beaches through the weekend.

FIRE WEATHER

Issued at 324 AM AST Wed Jun 24 2026

A tropical wave will move south of the region today, with its moisture field reaching the area and providing some relief in terms of RH values. Nevertheless, over southern of PR, relative humidities in the low 50s continue to be possible. Winds will be from the east- southeast at 10 to 20 mph, with gusts up to 33 mph, especially from mid morning into the afternoon. Although a moderate fire danger risk is forecast, a Fire Danger Statement could be issued later today if the moisture field from the tropical wave moves further south, giving way to a high fire danger risk. An elevated heat risk will also persist over the area and Saharan Dust concentrations will gradually increase as the day continues.

SJU WATCHES/WARNINGS/ADVISORIES

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