Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
822 FXUS66 KSGX 211145 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 445 AM PDT Fri Jun 21 2024 .SYNOPSIS... Hot today and then even hotter on Saturday as high pressure builds over the Four Corners region. A surge of monsoon moisture on Sunday will bring higher humidity and a slight chance for thunderstorms. Hot weather will continue in the valleys, mountains and deserts through Thursday with high pressure anchored over the desert southwest. A shallow marine layer will keep coastal highs in the 70s and 80s. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A dome of hot air associated with a massive area of high pressure over Texas will steadily drift west toward the Southwestern U.S. this weekend, then remain nearly stationary over the Four Corner region through most of next week. Today will be hotter than yesterday, and Saturday will be an even hotter day when Heat Advisories are in effect for the mountains and valleys. In the High Deserts, an Excessive Heat Watch is in effect Saturday and Sunday. In the Lower Deserts, an Excessive Heat Watch is in effect Saturday through Thursday with the heat dome stagnating over the eastern California deserts. Highs in the Coachella Valley and the San Diego County Deserts will range from 110-116. On Sunday a surge of mid-level monsoon moisture will bring higher humidity which will make it harder to keep cool during any outdoor activities. Additionally, a weak easterly wave in the southeast flow around the Four Corners high will track across southern California. This shortwave interacting with the monsoonal moisture will destabilize the atmosphere sufficiently for possible showers and thunderstorms Sunday. && .AVIATION... 210945Z...Coast/Valleys...Low clouds increasing in coverage and extending locally into the valleys at this hour. Bases are 1100-1300 ft MSL with tops to 1700 ft MSL with local VIS 3-5 miles in BR over higher coastal terrain and western portions of the valleys. CIG impacts likely at KSAN and KCRQ until about 16Z, then at KSNA 11Z to 15Z. CIG and/or VIS impacts not expected at KONT or KSBD. Clearing to the coast will occur 15Z-18Z, with only patchy low clouds returning to the coast after 03Z Sat. Mountains/Deserts...Mostly clear with unrestricted VIS through Fri evening. West winds with gusts 20-35 kt through San Gorgonio Pass and other favored locations on the desert slopes and into the deserts will continue to weaken through Friday. .MARINE... A system moving by to the south will bring a small chance (less than 20%) of precipitation and a 10% or less chance of lightning Saturday night through Sunday. Otherwise, no hazardous marine conditions are expected through next Wednesday. See the Marine Weather Statement for more information on the potential for thunderstorms. && .BEACHES... There is a slight chance of a thunderstorm Saturday night through Sunday which could produce cloud-to-ground/cloud-to-water lightning strikes. Chances of a lightning strike near any particular beach are currently 10 percent or less Saturday night and Sunday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory from 10 AM Saturday to 8 PM PDT Sunday for Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire. Heat Advisory from 10 AM to 8 PM PDT Saturday for Riverside County Mountains-San Bernardino County Mountains-San Diego County Mountains-San Diego County Valleys. Excessive Heat Watch from Saturday morning through Sunday evening for Apple and Lucerne Valleys. Excessive Heat Watch from Saturday morning through Thursday evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Moede AVIATION/MARINE...PG