Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
124 FXCA62 TJSJ 300855 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 455 AM AST Thu May 30 2024 .SYNOPSIS... A tropical wave will pass mainly south of the region today. A Saharan Ar Layer will bring hazy skies on Friday. Diurnally induced afternoon showers and thunderstorms are expected each day, mainly across the interior and western Puerto Rico. Another tropical wave is expected to cross the local area late in the weekend. A wetter pattern is forecast for next week. Warm to hot conditions expected across most lower elevations of the islands during the next several days. && .SHORT TERM...Today through Saturday... Overnight observations from satellite and radar indicated moderate shower activity over the local Atlantic and Caribbean waters. Some of this activity moved inland over the eastern municipalities of Puerto Rico, and Vieques. Doppler radar estimated rainfall accumulations between 0.5 to 1.0 inches in Naguabo, Ceiba, Fajardo and Vieques. Minimum temperatures were observed in the upper 70s to low 80s along the coastal and urban areas, and in the mid to upper 60s across the mountains. East to southeasterly winds of less than 10 mph prevailed through most of the night. Variable weather conditions are expected today due to the proximity of a tropical wave and its associated moisture field. The latest precipitable water content guidance continues to suggest normal to above normal values around 2.0 inches. As the wave passes south of the region over the Caribbean waters, an increase in moisture will enhance the development of showers and thunderstorms in the afternoon hours. The northwestern municipalities of Puerto Rico can expect the most activity in the afternoon through early evening, due to the southeasterly wind flow in combination with daytime heating and local effects. Conditions will gradually improve as the evening comes by. A mass of drier air is expected to filter into the region by Friday. However, this airmass will come accompanied by moderate concentration of Saharan dust that will last through Sunday. On Saturday, similar weather conditions are expected with limited shower activity. Despite of the presence of the drier airmass, active afternoons are expected to persist each afternoon across the interior and northwestern portions of Puerto Rico. The risk of excessive rainfall and lightning remains limited for the weekend. However, minor flooding is possible with the heaviest rains. Warm to hot temperatures will continue for the next several days under moist east to southeasterly winds. Heat indices are expected to range from 104 to 111 degrees Fahrenheit along the northern and western portions of Puerto Rico and St. Croix. Therefore, a Heat Advisory will be in effect starting at 10 AM AST today for the mentioned areas. .LONG TERM...Sunday through Thursday... There will still be some Saharan dust over the region as the Saharan Air Layer weakens during the weekend. A tropical wave is forecast to cross the islands on Sunday. This will bring an increase in shower activity first across the U.S. Virgin Islands, then spreading across Puerto Rico during the peak time of afternoon convection. Some thunderstorms could be strong over western PR. For next week, a mid-to upper-level trough is expected to move from the western Atlantic into the northeastern Caribbean, while a deep layered ridge builds and hold just east of the Leeward Islands. This will promote divergence aloft and a south to southwesterly wind flow at lower levels. In addition, a surface front associated to the upper trough will sink southwards but should remain above 20N. However, pooling of moisture is expected in general across the northeastern Caribbean through the long term period with global models suggesting between 2.10-2.40 inches of precipitable water content over the local area, peaking by midweek. The southerly winds and high humidity content will also promote warm to hot conditions across the islands, particularly across St. Croix and most coastal municipalities of PR. && .AVIATION... (06z TAFs) Mainly VFR conds expected across all terminals. SHRA will continue to move into from the Caribbean waters and Anegada passage and VCSH expected at TJSJ/TIST/TISX thru 30/14z. Aftn SHRA/TSRA may cause tempo MVFR conds at TJSJ/TJBQ btw 30/17-23z. Winds will prevail from the ESE at 10-15 kts with higher gusts and sea breeze variations aft 30/14z. && .MARINE... A moderate east to southeast wind flow will prevail across the region over the next few days. The next tropical wave will move far to the south of Puerto Rico and the U.S. Virgin Islands between today and early Friday. Thunderstorms are expected to develop once again today, between the late afternoon and evening hours across the western waters of Puerto Rico. && .BEACH FORECAST... A low to moderate risk of rip currents will continue today across most beaches of the U.S. Virgin Islands and Puerto Rico. Isolated thunderstorms are expected this afternoon across the northwest coast of Puerto Rico. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon for PRZ001-005-008-010. VI...Heat Advisory from 10 AM this morning to 4 PM AST this afternoon for VIZ002. AM...None. && $$ SHORT TERM...GRS LONG TERM....DSR