Marine Weather and Tide Forecast for Mayaguez, PR

SHORT TERM
Today through Sunday...

A deep layered trough west/northwest of the area will continue to move eastward and over the local area through the rest of the short- term period. A cut-off low at the upper levels is forecast to develop and sink further southward just north of Puerto Rico by Saturday afternoon. This will promote unstable and favorable conditions for shower and thunderstorm development across portions of the islands and the local waters. A broad surface high pressure over the central Atlantic will continue to support moderate to locally fresh ESE winds through at least this evening. However, lighter winds with a southeasterly component will prevail during the weekend as an induced surface trough develops over the northeastern Caribbean. In terms of moisture content, the precipitable water content is still expected to range between 1.80-2.00 inches between this evening and Saturday afternoon. However, a weak Saharan Air Layer will continue to bring minor concentrations of Saharan dust into the weekend and hazy conditions will be present across the USVI and PR. Having said that, we are still expecting thunderstorms with periods of locally heavy rainfall across the islands during the next 24 hours or so. Therefore, the main weather hazards continue to be the excessive rainfall that can lead to urban and small stream flooding, as well as localized flash flooding and mudslides in areas of steep terrain. On Saturday, due to the proximity of the cut-off low, the thunderstorms can produce frequent lightning and strong gusty winds.

LONG TERM
Monday through Thursday...

From Prev Discussion Issued at 515 AM AST

Recent model guidance shows no significant changes. A dynamic interplay between upper-level and surface features will continue to drive periods of marginal instability across the northeastern Caribbean. A Tropical Upper Tropospheric Trough (TUTT) Low will keep lifting northeastward and will likely exit the region by Monday. A second short-wave upper-level trough will follow, settling into the region starting Tuesday. This second feature will help sustain the developing mid-level ridge over the western Caribbean, reinforcing a marginally unstable weather pattern across the local area.

At the surface, a weakening induced trough will continue to disrupt the trade wind flow, keeping winds lighter and more variable early in the week. A broader surface high over the central North Atlantic will help trap tropical moisture across the eastern Caribbean, while a weaker high lifting northeastward over the western Atlantic will help push most of that moisture south of the local islands. As this high dissipates, east-southeasterly winds will likely strengthen and become more established by midweek, continuing through the latter part of the week. This pattern shift will not only support a gradual increase in tropical moisture but may also lead to warmer-than-normal conditions.

The combination of moisture and marginal instability will continue to favor shower and thunderstorm development, especially in the afternoons, due to daytime heating and local effects. Starting Wednesday, conditions will likely become more favorable for deeper thunderstorm activity as 500 mb temperatures drop to near-normal levels for this time of year, below -6 °C, through the second half of the week. Light winds, particularly through Tuesday, will limit storm movement and ventilation, allowing showers and storms to linger longer over the same areas, increasing the potential for locally heavy rainfall and flooding.

Meanwhile, Saharan dust will continue over the region, with concentrations likely peaking on Monday. This could temporarily suppress rainfall and lower air quality, especially across the Virgin Islands and eastern Puerto Rico.



AVIATION

(18Z TAFs)

SHRA/TSRA is expected to increase through the period. Therefore, tempo MVFR to brief IFR conditions are possible at times across all terminals through Saturday. Minor concentrations of Saharan dust will continue to filter across the local area, but VSBY will remain P6SM, except in areas of SHRA/TSRA. The 16/12z TJSJ sounding indicated ESE winds up to 23 kt blo FL030.



MARINE

A broad surface high pressure over the central Atlantic will continue to promote moderate to locally fresh easterly winds through tonight.
As a result, small craft should continue to exercise caution. Over the weekend and into early next week, a surface trough will gradually weaken these winds. At the same time, a deep trough to the west of the region will support an unsettled weather pattern, with a high chance of thunderstorm development through at least Saturday. These storms could lead to locally higher winds and seas. In addition, hazy conditions are likely over the next few days due to the presence of Saharan dust.



BEACH FORECAST

Life-threatening rip currents are possible along most northern and east-southeast exposed beaches of the islands today and tonight.
The risk will likely diminish by Saturday as winds ease gradually.
However, moderate rip current risk will likely return for Saint Croix early next week. For more information, please refer to the latest Coastal Hazard Message (CFWSJU) and Surf Zone Forecast (SRFSJU).

Shower and thunderstorm activity will likely increase into the weekend as the region transitions back to a wet and unstable weather pattern. Reminder: Seek shelter and leave the water or beach immediately at the first sign of thunder or lightning.



HYDROLOGY

Abundant moisture and increasing instability associated with an approaching upper-level trough will heighten the risk of flooding across Puerto Rico and the U.S. Virgin Islands through Saturday.
With saturated soils and elevated river levels in some areas, any additional heavy rainfall could lead to urban and flash flooding, river flooding, and landslides, even after the heaviest rain has ended. For more details, please refer to the Hydrologic Outlook (ESFSJU).



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