SHORT TERM
Today through Monday...

Hazy skies due to a strong Saharan Air Layer will prevail through at least early Sunday. Hot temperatures are expected to continue today with heat indices expected to range from 106 to 112 degrees Fahrenheit, mainly along the lower elevations of western, southern and northern Puerto Rico, and St. Croix. Therefore, a Heat Advisory (NPWSJU) was issued across these areas, and could likely be issued once again on Sunday and Monday as the SAL exits the region and dewpoints increase. Although shower activity will be limited in general, diurnally induced streamers developing off the USVI and smaller islands and showers with possible isolated thunderstorms could still develop during the afternoons over portions of west/southwest PR.

On Monday, a TUTT induced trade wind perturbation or weak trough is expected to move from the east and bring an increase in moisture content. Precipitable water content could increase between 1.75-2.00 inches by Monday afternoon. Therefore, showers will increase in coverage as well as the potential for better organized afternoon convection over the interior and western Puerto Rico. Urban and small stream flooding can be expected with this activity. Drier conditions and hazy skies will follow quickly by Monday night as a weak Saharan Air Layer filters from the east.

LONG TERM
Tuesday through Saturday

A seasonal weather pattern will prevail on Tuesday, with slightly below-normal to near-normal moisture levels across the forecast area. This will bring occasional trade wind showers over windward coastal areas during the morning hours and a few isolated thunderstorms across western Puerto Rico.

Afterward, forecast details become more complicated as several features will reach the northeastern Caribbean by mid-week.
Troughiness aloft will promote favorable weather conditions conducive to convective development. At low levels, a wind surge will first reach the local islands by early Wednesday, bringing gusty wind conditions and squally weather to the region. From the rest of the day through Thursday, a vigorous tropical wave behind the wind surge will increase moisture content to well above normal levels, in some instances reaching close to 2.40 inches. The National Hurricane Center is currently monitoring the tropical wave with a low formation chance in the next seven days. However, uncertainty remains as some global models now predict the tropical wave developing after it passes the CWA The timing also differs between models, with the ECMWF forecasting the tropical wave arriving and exiting the region earlier than the GFS model.

Adding to this complex scenario is the presence of another Saharan Air Layer event engulfing this tropical wave. The Saharan dust particulates could be another limiting factor for shower and thunderstorm activity. The rest of the week will depend on the behavior of this tropical wave. The GFS model predicts lingering moisture lasting through the weekend, potentially prolonging the wet and unstable weather period.

Forecast confidence is low regarding the impact of this tropical wave on the forecast area for next week. Therefore, continue to monitor the forecast, as slight deviations in the tropical wave's path and intensity could change the expected impacts across the local islands. Regardless of the outcome, we can expect a shift in weather conditions with increased instability and an elevated flooding threat. This could potentially bring heavy rain, frequent lightning, and gusty winds. Quick river rises and landslides cannot be ruled out as this tropical wave crosses the northern Caribbean.



AVIATION
(06Z TAFs)

Mainly VFR conditions expected to prevail across all terminals thru the next 24 hours. HZ due to Saharan dust may reduce visibilities around 6SM through the forecast period. East to northeast winds increasing at 15-20 kts, with stronger gusts and sea breeze variations aft 27/14Z. -RA/VCSH expected early in the morning at TJSJ/TJBQ, and btw 27/18z-22z at TJPS.



MARINE

Surface high-pressure located in the central Atlantic will continue to support moderate to locally fresh easterly winds and choppy seas for small crafts over the next few days. A strong Saharan dust event will continue to affect the local islands at least until early Sunday, resulting in hazy skies and limiting shower activity.
By mid-week of next week, a vigorous tropical wave will promote shower and thunderstorm activity across the regional waters along with hazardous seas.

BEACH FORECAST

Increasing winds this weekend into early next week will promote moderate risk of rip currents for north- and east-facing beaches.
A vigorous tropical wave will reach the local islands by mid-week of next week. This will increase shower and thunderstorm activity across the area. Gusty wind conditions could increase rip current risk to high in some beaches as well.

SJU WATCHES/WARNINGS/ADVISORIES
PR...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for PRZ001-003-005-007-008-010-011.

VI...Heat Advisory from 10 AM this morning to 5 PM AST this afternoon for VIZ002.

AM...None.