Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
177 FXCA62 TJSJ 011705 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 105 PM AST Tue Jul 1 2025 .KEY MESSAGES... * Trade wind showers will increase tonight across the islands. * Breezy winds will sustain choppy seas and maintain a moderate risk of rip currents along exposed beaches over the next few days. * A tropical wave is forecast to increase shower activity by Friday. However, a strong Saharan Air Layer with moderate to high concentrations of Saharan dust is expected to move with the wave into the weekend. && .SHORT TERM...Tonight through Thursday... Sunny to partly cloudy skies prevailed across the islands throught the day. Afternoon showers were developing over the southwestern quadrant of Puerto Rico, and streamers were developing downwind of the U.S. Virgin Islands. Additional showers are expected later this evening and tonight as a wind surge with showers embedded in the trades reach the local area. Maximum temperatures were from the mid-80s to the low 90s across the lower elevations of the islands, and from the mid-70s to low 80s across the higher mountains of Puerto Rico. The wind was from the east to northeast between 15 and 20 mph with sea breeze variations and higher gusts across coastal areas. A mid-level ridge north of the area will continue to move west and away of the local area today, while a trade wind perturbation bring an additional moisture content through Wednesday morning. This will cause mostly passing showers across the USVI and eastern sections of PR. Thereafter, a surface high pressure will build over the central Atlantic and winds will turn more ESE through at least Thursday. Overall fair weather conditions are expected for the rest of the short-term period. However, diurnally induced afternoon showers are expected to develop each day over western PR. A limited heat risk is expected across most coastal areas as daytime temperatures reach the low 90s and the absence of Saharan dust will cause relative humidities to increase in general across the western, northern, and eastern sections of the islands. .LONG TERM...Friday through Tuesday... /From Prev Discussion issued at 432 AM AST Tue Jul 1 2025/ A weak tropical wave will approach the islands on Friday. The bulk of the wave will remain over the Caribbean Sea, but enough moisture should trigger some showers over the Virgin Islands and Puerto Rico, with stronger convection developing across western Puerto Rico in the afternoon. Just like the last wave that moved over the region, this one also comes with a lot of Saharan dust, so skies will be hazy late on Friday and on Saturday. Later on the weekend and early next week, a series of surface troughs will also move into the region, but they will also be embedded in Saharan dust. The pattern aloft will not favor deep convection, but occasional showers will move into the islands at times, with additional showers and isolated thunderstorms each afternoon across the west. The winds will be driven by a surface high pressure over the eastern Atlantic, at 10 to 16 kts. It will be hot too, as it is expected for July, with heat indices above 102 degrees along all coastal and urban areas in the region. && .AVIATION... (18Z TAFS) VFR conditions are expected to prevail across all terminals through the period. However, quick passing -SHRA will move at times across the USVI/Eastern PR terminals during the night. This may cause brief MVFR conds. The 01/12z TJSJ sounding indicated ENE winds up to 26 kt blo 4000 ft. && .MARINE... Mariners can expect choppy seas across the local Atlantic and Caribbean waters due persistent moderate to fresh easterly winds. A weak tropical wave is forecast to move over the local waters on Friday, increasing shower and thunderstorm chances. Saharan dust will follow the tropical wave, with hazy skies returning quickly through the weekend. && .BEACH FORECAST... A moderate risk of rip currents (life-threatening rip currents are possible in the surf zone) are expected for most northern, east, and southern beaches of Puerto Rico, as well as for beaches of Culebra, Vieques, southern St. John, southern St. Thomas and all but western St. Croix. Life-threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers. Up to a moderate risk of rip currents will remain for most of the period. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ DSR/MMC