Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
516 FXCA62 TJSJ 212009 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 409 PM AST Fri Jun 21 2024 .SYNOPSIS... Trailing showers will continue to move over the the islands during the overnight hours into Saturday morning. Typical summer weather conditions will persist for the next several days with afternoon convection producing heavy showers and thunderstorms over the interior and western Puerto Rico. A series of tropical waves will approach the area by early next week. && .SHORT TERM...Tonight through Sunday... Trailing showers were observed across the islands during the morning hours, leaving minor accumulations over the eastern Puerto Rico and the U.S. Virgin Islands. Variable weather conditions persisted through the afternoon hours, with the development of stronger showers and isolated thunderstorms. The activity concentrated over portions of central and western Puerto Rico. Doppler radar estimated between 1.0 to 2.0 inches of rain between Maricao and Mayaguez. Flood Advisories were issued for the mentioned areas. Winds prevailed from the east between 15 to 20 mph with higher gusts. Daytime temperatures were seen between the upper 80s to low 90s across most of the region with heat indices in the mid to upper 100s. A surface to mid level high pressure over the central Atlantic will continue to promote easterly winds through Saturday, then veering from the east southeast from early Sunday onward. Moderate to locally fresh winds will continue to persist until early next week, resulting in the arrival of fast moving trade wind showers through the rest of the period. Afternoon convective activity is expected everyday across portions of the interior and western Puerto Rico with the potential of moderate to heavy showers and isolated thunderstorms. Lower concentrations of Saharan dust are expected to arrive this weekend, resulting in hazy skies. Daytime temperatures will remain hot across the region, with highs in the range between the upper 80s to lower 90s along the coastal and urban sectors, and in the mid 80s in the mountains. Heat indices are expected to be elevated as well, with a limited heat risk anticipated. .LONG TERM...Monday through Friday... ./FROM PREV DISCUSSION...Issued at 419 AM AST Fri Jun 21 2024/ A robust surface high stretched across the central Atlantic will maintain a pattern of trade wind showers followed by afternoon convection across the islands throughout the week. Plenty of moisture remains over the area with constantly high precipitable water values which will yield in an abundance of showers at times. On Monday, a tropical wave begins to move across the area, bringing unstable conditions across the the lower levels that will aid in thunderstorm development across the area. Generally relatively high pressure will remain across the mid to upper- levels during this time, however with the instability caused by the tropical wave and a continued east to southeasterly flow, rain may be persistent and heavy a few time throughout this period. The movement of an area of low pressure north of the region by mid-week will help maintain high precipitable water values as easterly flow pushes a moist airmass over the region. Afternoon convection due to local effects and diurnal heating will play a big role in allowing thunderstorms to form, with western Puerto Rico most likely to receive the bulk of rain and the greatest risk of excessive rainfall. && .AVIATION... (18Z TAFs) Iso TSTMs over interior PR should cause mostly VCTS across TJSJ/TJBQ/TJPS thru late this afternoon. Trade wind SHRA will continue to move at times across the USVI and eastern PR terminals thru Sat morning. This may cause brief MVFR conds at TIST/TISX/TJSJ. Otherwise, mainly VFR conditions expected to prevail. East winds will continue at 12-18 kt with higher gusts thru 22z, bcmg light and variable overnight. && .MARINE... A surface high pressure over the central Atlantic will promote moderate to locally fresh easterly winds through the rest of the week. Trade wind showers will move across the regional waters from time to time. The next tropical wave will approach the local islands by the beginning of the next workweek. && .BEACH FORECAST... A moderate risk of rip currents is present for the northern exposed beaches of Puerto Rico and St. Croix. Remember, life-threatening rip currents are possible in the surf zone. A low risk of rip currents will be present from Saturday onward. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...CAM LONG TERM....GRS AVIATION...DSR PUBLIC DESK...MRR