380 FXCA62 TJSJ 172044 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 444 PM AST Thu Oct 17 2024 .SYNOPSIS... Invest 94L, will move north of the islands on Friday and Saturday, bringing an increase in showers and thunderstorms. Advancing tropical moisture and the approach of 94L will combine to bring even more showers and thunderstorms from the weekend into next week. A northerly swell will arrive late in the weekend and early next week, causing marine and coastal conditions to deteriorate. .SHORT TERM...Tonight through Saturday... Wet and unstable conditions prevailed today as patches of moisture passed through the islands. Based on Doppler radar estimates, trade wind showers left rainfall accumulations around 1-2 inches over the western and near the Ponce area. Flood advisories were issued for the western section and the San Juan metropolitan area. A heat advisory was in effect until 4:00 PM for the urban and low-elevation areas of the north, west, and southwest through Santa Isabel as heat indices overpassed 108 degrees Fahrenheit. Occasional shower activity will continue through tonight. Overnight temperatures will drop to the upper 70s to low 80s along the urban and low elevations while upper 60s to low 70s in the higher terrains. The National Hurricane Center continues monitoring Invest 94L, with a low chance of cyclone formation of 20% in the next 48 hours and 30% during the next 7 days. The system will approach Puerto Rico and the US Virgin Islands tomorrow, gradually increasing the potential for shower and thunderstorm activity through Saturday. Ponding of water in roadways and poorly drained areas is likely, with urban and small stream flooding mainly across the east, interior, and west sections of Puerto Rico. && .LONG TERM...Sunday through Thursday... PREV DISCUSSION... /issued 718 AM AST Thu Oct 17 2024/ A cold front will dig just north of the Central Caribbean by Sunday. This system will gradually cause the winds to shift to the south southeast through Wednesday, carrying moisture from the Caribbean Sea that will converge over the local islands. As a result, showers and thunderstorms will increase in frequency, and could be heavy at times. The risk of flooding will be elevated, with potential for mudslides in areas of steep terrain, as well as rapid river rises. The eastern and southern portions of Puerto Rico, as well as the Virgin Islands are the areas with the highest probability of precipitation. The days with the best potential for rain are from Sunday to Tuesday. By Wednesday, conditions will begin to dry out, but gradually. Moisture will linger at the surface, so some showers are still anticipated. This break will not last long, as more moisture is expected to reach the eastern Caribbean by Thursday and Friday. It should be noticed that if a dense cloud coverage develops, it could work to lower the temperatures a little. However, if sunshine peeks through, the deep-layer south flow will cause it to feel very muggy and steamy. && .AVIATION... (18Z TAFS) Sct SHRA/TSRA to cont thru 17/23Z ovr land and will cont byd 18/14Z ovr the lcl waters. Lcly obscured mtns and MVFR/IFR conds with SHRA/TSRA. LLVL winds E 10-15 kt with hir gusts in sea breezes and arnd TSRA. Max winds NE 30-40 kt btwn FL425-465. TSRA to diminish aft 17/22Z, but SHRA/isold TSRA to cont across ern PR/USVI and lcl water byd 18/14Z. Aft 18/14Z areas SHRA/isold TSRA with associated MVFR/IFR conds and mtn obscurations. && .MARINE... Surface high pressure over the eastern Atlantic will maintain a moderate easterly wind flow across the area. Invest 94L located east of the Leeward Islands will pass just north of the region on Friday. This will bring squally weather across the local waters from late tonight trough Friday night, particularly across the Anegada Passage and the Atlantic waters. By early next week, swells from a low pressure over the western Atlantic will spread across the Atlantic waters and passages. && .BEACH FORECAST... There is a moderate risk of rip currents for northern Puerto Rico, Culebra, and St. Croix. The risk will stay moderate through early this weekend, however, it could increase to high as a long-period northerly swell arrives early next week. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...MNG/MMC AVIATION...WS MARINE...MNG/DSR LONG TERM....ERG
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