240 FXCA62 TJSJ 220859 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 459 AM AST Wed Jan 22 2025 .SYNOPSIS... Shower activity is expected to increase in general through early Thursday morning due to a trade wind perturbation. Choppy wind- driven to hazardous seas will persist for most of the workweek, maintaining dangerous conditions for small craft and promoting life-threatening rip currents. Quick passing showers are expected to move from time to time over the USVI and eastern sections of PR. Shallow afternoon convection is possible over western PR each day. && .SHORT TERM...Today through Friday... Mostly fair weather, and breezy conditions, were observed overnight with passing showers embedded in the trades along eastern portions of Puerto Rico and the U.S. Virgin Islands. Doppler radar rainfall estimates ranged from 0.1 to 0.2 inches, with local amounts up to 0.3 inches over Rio Grande. Minimum temperatures in lower elevations remained in the 70s while higher terrains were observed in the lower to mid 60s. The short term forecast remains on track, with a variable weather pattern for the second part of the workweek. Current satellite image shows patches of moisture arriving into the region, and derived products show high moisture content over east of the Leeward Islands. The broad high surface pressure in the Central Atlantic continues promoting trade winds, which will remain for the next few days. A mid-to-high level ridge northeast of the region will maintain stable conditions aloft, unfavoring convection activity. The perturbation in the trades is expected to arrive later today, increasing PWAT values will increase up to 1.8 inches, above normal values based on the latest model guidance and climatology. This will promote frequent shower activity, from moderate to locally heavy, across the region, particularly starting today in the afternoon into Thursday morning. Rainfall accumulations over the eastern, eastern interior, and the San Juan Metropolitan Area in Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands. Although showers will move quickly, ponding of water in roadways, urban, and poorly drained areas is very likely, along isolated urban and small streams flooding. A drier air mass will arrive on Thursday, but patches of moisture will arrive bringing occasional showers. Low-level winds shifting from the E-ESE will promote above-normal 925 mb temperatures today, with maximum temperatures in lower elevations from mid 80s to upper 90s, and higher terrains from mid 70s to low 80s. .LONG TERM...Saturday through Wednesday... A deep-layered ridge is expected to presist over the Tropical Atlantic throughout the long-term period. A short-wave trough is expected to cause a brief weakness aloft over the region on Sunday, and a pre-frontal trough is expected to develop mainly north of the region during the weekend. Another upper level trough is expected to move over the area on Tuesday, and the 500 mb temperatures are forecast to drop near -7C. However, the precipitable water content is forecast to remain at normal to below normal levels through the entire forecast period, and showers across the area will be driven mostly by the remnants of old frontal boundaries that the trade winds will carry from time to time. Normal to above-normal temperatures are expected to prevail throughout most of the long-term period, particularly in the coastal and lower elevations of the islands. Daytime highs will range from the mid to upper 80s and low 90s in coastal and urban areas, while the mountains will experience highs in the mid to upper 70s. Minimum temperatures will range from the low 60s in the higher elevations to the mid and upper 70s in the lower elevations of the islands. && .AVIATION... (06z TAFs) Mostly VFR conds expected at TAF Sites. Perturbation in the trades will arrive today, with -RA/+RA for TISX, TIST starting at 22/13z and for TJSJ at 22/22z. Reduced CIG/VIS may promote brief periods of MVFR conds from 22/18z to 23/06z. E-ESE winds from 8-12 kt and gusty winds up to 20 kt. && .MARINE... A surface high pressure across the central Atlantic will support moderate to locally fresh easterlies for the next several days. Choppy wind-driven to hazardous seas for small craft will continue across portions of most local waters and passages. Small craft advisory conditions are likely to continue through the end of the workweek. Increased shower activity will continue through early Thursday morning. && .BEACH FORECAST... A high risk of rip currents is in effect for the north oriented beaches of Puerto Rico, as well as for Culebra and easternmost Vieques. A moderate risk of rip currents is in effect for most other areas. Choppy wind-driven seas will continue to promote up to a high risk of rip currents through the end of the week. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late Thursday night for PRZ001-002- 005-008-012. VI...High Rip Current Risk through late Thursday night for VIZ002. AM...Small Craft Advisory until 6 AM AST Friday for AMZ711-723. Small Craft Advisory until 6 AM AST Thursday for AMZ712-716-726- 733-741. && $$ SHORT TERM...MMC LONG TERM....DS AVIATION...MNG
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