Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
451 FXCA62 TJSJ 290818 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 418 AM AST Sat Jun 29 2024 .SYNOPSIS... A tropical wave is expected to move across the local area today promoting afternoon convective activity over western Puerto Rico and downwind of the smaller islands. Hot conditions are also expected today across the region, and a Heat Advisory is in effect for most of the coastal and urban areas of Puerto Rico and St. Croix. Tropical activity is anticipated next week, with the passage of Tropical Storm Beryl and a tropical wave south of the area and over the Caribbean Waters. && .SHORT TERM...Today through Monday... Trade wind showers and isolated thunderstorms increased throughout the night across the regional waters and over portions of the islands. The Doppler radar estimated around half an inch of rain over eastern Puerto Rico. Minimum temperatures ranged from the upper 60s to mid-70s across the higher elevations and from the upper 70s to low 80s across coastal municipalities. Winds were around 10 mph from the east. It will be hot again across the islands, and a Heat Advisory (NPWSJU) was issued for St. Croix and the north, south, and western coastal counties of Puerto Rico. Maximum temperatures should reach the low 90s across the lower elevations, with heat indices ranging between 108F and 112F. Although mainly east winds prevail at the surface, an east-to- southeast steering wind flow is expected today as a tropical wave moves across the eastern Caribbean. Shower activity will continue to increase in coverage, as will thunderstorms across the local waters. Urban and small stream flooding is expected, particularly across western PR during the afternoon. Trailing the wave, a Saharan Air Layer with moderate amounts of Saharan dust should cause hazy skies across the USVI by this afternoon. On Sunday and Monday, drier air will continue to filter across the islands, with suspended Saharan dust, causing hazy skies and limiting the potential for shower activity throughout most of the period. Although isolated to localized scattered showers cannot be ruled out, particularly during the afternoon, excessive heat threat will continue as warm temperatures prevail across the northeastern Caribbean and combine with the Saharan Air Layer. Weather conditions will quickly deteriorate during the night as the outer bands from TC Beryl bring showers and thunderstorms across the local area. Squally weather with strong gusty winds is possible across portions of the Caribbean waters, the USVI, and east/southern PR through early Tuesday. .LONG TERM...Tuesday through Saturday... Tropical activity will dominate much of the long term period with the presence of Tropical Storm Beryl and a vigorous tropical wave in the Eastern Tropical Atlantic. The National Hurricane Center (NHC) is monitoring Tropical Storm Beryl located in the Central Atlantic that it is forecast to become a hurricane before reaching the Lesser Antilles. Latest model guidance suggest that Beryl will stay well south of the local islands as a category 2 hurricane. At this moment, the closest point to Puerto Rico and the U.S. Virgin Islands will be on Tuesday. Despite this system staying south of the islands over the Caribbean waters, a broad field of moisture and external bands could reach the local area. Therefore, an increase in showers and thunderstorm activity associated to this system is anticipated. With the expected conditions, some potential hazards are: flooding, mudslides, and river rises. A drier airmass will quickly follow Beryl as it moves away from the region towards The Hispaniola. This drier airmass will bring some Saharan Dust particles promoting slightly hazy skies. However, this dry weather pattern will not last long due to the fast approach of a tropical wave behind Beryl with the potential of becoming a tropical cyclone. Model guidance suggest the development of this wave, and moving this system close to the local area by Thursday. Similarly to Beryl, this wave is nor expected to have direct impacts over Puerto Rico and the U.S. Virgin Islands. However, it is expected to bring shower activity over the region. Residents and visitors of Puerto Rico and the U.S. Virgin Islands should continue to monitor the progress of both systems as they move towards the Caribbean over the next few days. && .AVIATION... (06Z TAFS) SHRA/TSRA expected to increase across the local area due to a tropical wave passage across the Caribbean Sea. Tempo MVFR conditions are possible in and around TJPS/TJSJ/TJBQ btw 29/15z-21z. Across the USVI terminals, mostly VFR conditions are expected with VCSH prevailing thru the mid afternoon hours. HZ due to Saharan dust will gradually increase across the USVI terminals into eastern PR before sunset. East winds at 12-16 kt with stronger gusts and sea breeze variations aft 29/14z. && .MARINE... A surface high pressure over the central Atlantic will promote light to moderate easterly winds. Trade wind showers will move across the regional waters from time to time due to a tropical wave moving south over the Caribbean Waters today. Tropical Storm Beryl is forecast to strengthen as it approaches the Caribbean waters late Monday night into Tuesday, deteriorating marine and coastal conditions considerably for the Caribbean and local passages. && .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. && $$ SHORT TERM...DS LONG TERM....GRS