Marine Weather and Tide Forecast for Lomas, PR

SHORT TERM
Tonight through Tuesday...

Radar and satellite data indicated calm weather conditions across most of the forecast area during the morning, with the exception of isolated to scattered showers over parts of eastern and northeastern Puerto Rico and the adjacent eastern local waters.
Radar-estimated rainfall accumulations generally remained at or below 0.50 inches; however, between Dorado and Toa Baja, totals ranged from approximately 1 to 1.5 inches. By midday, increasing cloud cover was observed, and showers began developing from the interior toward northwestern Puerto Rico. A strong thunderstorm in that area prompted the issuance of a Special Weather Statement.
As expected, winds became breezier today with an easterly component. The highest wind gusts recorded were 29 mph at San Juan International Airport and 30 mph at Ponce Airport. As of 1 PM AST, daytime maximum temperatures ranged from the mid to upper 80s to low 90s across low elevation and urban areas.

The forecast remains on track for the rest of the afternoon, with additional development of convection and isolated thunderstorms expected. Moisture levels have slightly decreased compared to yesterday, but they remain near normal for this time of year, as indicated by model guidance and the 12Z sounding, which showed 1.86 inches of precipitable water. As a result, available moisture will continue to result in localized convection with thunderstorms, particularly across the northwestern quadrant of Puerto Rico and the San Juan metropolitan area, where streamer formation is contributing to enhanced activity. The flood risk remains elevated in these areas, with potential impacts to urban zones, roadways, and small streams. Shower activity is expected to decrease significantly after sunset, leading to calmer conditions during the evening. Additional rainfall is anticipated overnight, especially across eastern Puerto Rico, the U.S. Virgin Islands, and surrounding waters, though significant accumulations are not expected.

By the beginning of the workweek, Monday and Tuesday, more stable conditions are anticipated even though localized afternoon convection will remain possible due to daytime heating and local effects across western Puerto Rico. The upper level trough will continue moving away from the region, while a mid-level ridge begins to establish itself. Winds will gradually turn from the east to east-northeast, a decrease in moisture levels to around 1.4 to 1.6 inches, and rising mid-level temperatures to approximately -5 to -6°C. Like previously mentioned, afternoon showers may still develop due to local effects, but their coverage and intensity are expected to diminish early in the workweek. As a result, the flood risk should become limited to none these days.

LONG TERM

PREV DISCUSSION
/issued 522 AM AST Sun May 11 2025/

The long-term forecast will begin with a generally stable pattern over the region, under the influence of a mid to upper-level ridge centered over the western Caribbean and Puerto Rico. This ridge places the islands on its subsident side, favoring stable conditions aloft, as supported by rising 250 mb heights and gradually warming 500 mb temperatures from around -7°C to near -5°C by the end of the workweek, according to GFS. From midweek through Thursday, a pronounced trade wind inversion will help suppress deep convective activity. However, precipitable water values are expected to range between 1.5 and 1.7 inches, and 700–500 mb relative humidity will increase at around 40 to 50 percent. These values may still support isolated afternoon showers, particularly across the interior and western Puerto Rico.
Overall instability will remain limited, which will help keep rainfall coverage and intensity in check. Later in the period, model guidance shows a transition to a wetter and more unstable pattern.

As the mid to upper-level ridge weakens, an upper-level trough will move eastward, lowering 500 mb temperatures and weakening the trade wind inversion. A surface trough is forecast to develop as well, shifting winds from the east-southeast to a more southerly component, which will allow for deeper tropical moisture to move into the region. As a result, precipitable water values are expected to exceed 2.0 inches by the weekend. By the weekend, the environment becomes significantly more conducive to enhanced convection, with increasing mid-level moisture and a more unstable atmospheric profile. These conditions will support widespread showers and thunderstorms, particularly across the Cordillera Central and western Puerto Rico, aided by diurnal and orographic effects. This pattern will likely peak in activity during the weekend, when conditions will favor more organized convection and higher rainfall totals. Localized flooding is possible. Residents and visitors should stay alert for updates in case weather advisories or special statements become necessary.

AVIATION
(18Z TAFs)

Localized areas of SHRA/TSRA are expected with local MVFR conds TJBQ/TJSJ/TIST and mtn topping in wrn and interior PR through 23z.
Sfc ESE winds of 10-18 kts with gusts to 25-28 kt psbl. Winds subsiding to arnd 10 kts aft 11/22Z.

MARINE

Beachgoers can expect a low to moderate risk of rip currents across the local beaches. However, remember that rip currents often occur near groins, jetties, reefs, and piers. The risk of rip currents will remain moderate for the next few days across northern and eastern exposed beaches.

BEACH FORECAST

Beachgoers can expect a low to moderate risk of rip currents across the local beaches. However, remember that rip currents often occur near groins, jetties, reefs, and piers. The risk of rip currents will remain moderate for the next few days across northern and eastern exposed beaches.

SJU WATCHES/WARNINGS/ADVISORIES
PR...None.
VI...None.
AM...None.