


Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
262 FXCA62 TJSJ 081800 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 200 PM AST Tue Jul 8 2025 .KEY MESSAGES... * Moderate to high concentrations of Saharan dust are expected to return during the second part of the workweek, resulting in hazy skies, reduced visibility, and poor air quality. * Breezy conditions are expected through Wednesday. Choppy seas and a moderate risk of rip currents will persist over the next few days. These may create hazardous conditions across the Atlantic waters. * Diurnally induced afternoon showers and isolated thunderstorms are expected over portions of the Cordillera Central and western PR each day. Passing showers will continue across the USVI and eastern sections of PR during the night/early morning hours. && .SHORT TERM...Today through Thursday... Sunny to partly cloudy skies were observed across the islands today. Diurnally induced showers and isolated thunderstorms were developing over the northwest quadrant of Puerto Rico early this afternoon, and are expected to continue over the western waters of PR thru this evening. Maximum temperatures were from the upper-80s to the low 90s across the lower elevations of the islands, and from the mid-70s to mid-80s across the higher mountains of Puerto Rico. The wind was from the east to southeast between 16 and 22 mph with sea breeze variations and higher gusts between 32 and 37 mph observed across coastal areas of all the islands. A wind surge will bring scattered showers and stronger winds across the area from tonight through Wednesday. Another tropical wave with a band of moisture of 1.80 inches of precipitable water will stream across the area on Thursday. However, higher concentrations of Saharan dust mixed with the tropical wave could hinder shower activity in general. Having said that, the overall available moisture content is forecast to remain around normal levels, fluctuating in general between 1.50-1.80 inches through at least Thursday afternoon. Therefore, we expect a similar weather pattern each day with passing showers across the USVI/eastern half of PR during the night/early morning hours, followed by diurnally induced afternoon showers and isolated thunderstorms developing over portions of central and western PR, and streamers developing downwind of the USVI and from el Yunque area. Most of this activity across PR will cause ponding of water on roads and poor drainage areas, and urban and small stream flooding where thunderstorms develop. At the lower levels, a broad ridge building from the central Atlantic will promote east to southeast winds for the next few days. The higher moisture content near the surface and these winds will promote normal to above normal temperatures each day and a limited heat risk will persist for the lower elevations and urban areas of the islands. Higher concentrations of Saharan dust on Thursday will promote hazy conditions and poor air quality. .LONG TERM...Friday through Tuesday... /From Prev Discussion issued at 500 AM AST Tue Jul 8 2025/ The inherited forecast remains on track. The latest model guidance continues to support a surface wind surge crossing the region on Friday, leading to a brief increase in low-level moisture. This may support isolated to scattered showers early in the day. However, a significantly drier air mass is expected to filter in by late Friday and continue through the upcoming workweek, suppressing widespread convection. At the same time, mid- to upper-level dry air and a reinforcing trade wind inversion will further limit vertical cloud development. Additionally, the arrival of a Saharan Air Layer will contribute to hazy skies, reduced visibility, and potential impacts on air quality, especially for sensitive groups. This dusty and dry environment will also act to suppress rainfall through Saturday. Breezy to windy conditions will prevail both Friday and Saturday, with easterly winds supporting above-normal temperatures, particularly in coastal and urban areas. By Sunday, the Tropical Upper-Tropospheric Trough (TUTT) is forecast to shift westward toward Hispaniola. This transition, combined with the approach of easterly trade wind disturbances, will begin to increase atmospheric moisture over the region. As a result, rain chances will rise on Sunday afternoon, with a more favorable environment for convection. Monday and Tuesday will likely feature the highest rainfall potential as deeper tropical moisture becomes established across Puerto Rico and the U.S. Virgin Islands. Scattered showers and thunderstorms are expected each afternoon, especially in western and interior sections. Although the threat of excessive rainfall remains low until late Sunday into Monday, other weather concerns. && .AVIATION... (18z TAFs) Mainly VFR conditions are expected across all terminals during the next 24 hours. However, SHRA/TSRA expected to develop in and around TJBQ thru 08/22z. Across the USVI terminals and TJSJ, mostly VCSH expected with brief periods of -RA. The 08/12z TJSJ sounding indicated ESE winds up to 27 kt blo FL120. HZ will gradually increase during the next day or so, but VSBY should remain P6SM. However, higher concentrations of Saharan dust return from Thursday onward and visibilities could drop to 5-6 SM. && .MARINE... Moderate to fresh trade winds will create choppy seas across local waters over the next several days, small craft should exercise caution. Small Craft Advisories will possibly be issued later on for Wednesday. Afternoon thunderstorms may impact coastal waters and local passages, particularly over western Puerto Rico and the Mona Passage each day. Showers and thunderstorm chances increase on through Thursday with the passage of tropical waves. Saharan dust is expected to return later in the workweek. && .BEACH FORECAST... Increasing winds over the next several days will promote a moderate risk of rip currents across the eastern, northern, and southeastern beaches of Puerto Rico, Vieques, Culebra, St. Thomas. and St. Croix. Life-threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ DSR/GRS