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Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
706 FXUS66 KSGX 261921 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1221 PM PDT Fri Jul 26 2024 .SYNOPSIS... The heat wave will end after Friday due to a weather disturbance that will move through northern California today and bring cooler and breezier weather for mountains and deserts across southern California into Saturday. Strongest wind conditions for Saturday afternoon and evening. Dry air has moved in from the north and will continue to spread southward resulting in lower humidity and has ended the monsoon. Greater coverage of morning low clouds is expected for coastal areas over the weekend with the low clouds becoming patchier again next week. Also for next week, there will be a gradual warming trend along with a slow increase in humidity. There is uncertainty when the next threat for thunderstorms occurs but slight chance for late next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Almost cloud free along beaches with small patches left and also clear inland with the air mass drying from north to south with precipitable water values decreasing further. There was an outflow that moved into the Coachella Valley early this morning and raised dewpoints but convection is not expected today though cumulus will form especially San Diego mountain desert slopes closer to the remaining monsoon moisture of 1.4 inch values. Notably stronger drier of under 1 inch precipitable water air mass now over San Gabriel and San Bernardino mountains per Storm Prediction analysis. Today is nearly as hot as yesterday for inland areas with air mass of 25-26C on the coast but up to 31 to 32C for inland deserts, so we still have moderate heatrisk in the Inland Empire and areas of major in the lower deserts. 109F at Palm Springs as of noon and same as yesterday. We finally have cooling of air mass for Saturday (22-28C at 850 mb level), in the wake of the disturbance that tracks across northern California. There is also a better push of more organized low clouds and marine air into the valleys. Fire weather conditions deteriorate because of drier air and increasing onshore flow for all deserts and the mountains with the peak of the westerly winds on Saturday. The coolest day for most areas will be Sunday. Weather pattern warms next week but still considerable uncertainty as potential upper level wave arrives during midweek from Mexico on the backside of the heat dome rebuilding over the Great Basin and 4-corners region. This could bring back monsoon moisture as well for late week. && .AVIATION... 261930...Coast...Low clouds with more uniform coverage will move ashore around 04-05Z and eventually cover coastal areas and western valleys overnight. Bases will be around 800-1200 feet MSL and local vis reduced 1-5SM on higher coastal terrain and western valleys. Scatter out Saturday by 15-18Z. Mountains/Deserts...Westerly winds gusting 25-35 kt gradually tapering off overnight through mountain passes into adjacent deserts. MOD up/downdrafts in lee of mountains. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .FIRE WEATHER... Elevated fire weather conditions Friday and Saturday afternoons due to the drier air, lower humidity, and increase afternoon and evening onshore west winds for the mountains and all deserts, especially the High Desert. && .CLIMATE... 4th time this year Palm Springs has hit 120F. The record is 5 set in 2020 and 2021. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning until 8 PM PDT this evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Tardy AVIATION/MARINE...MM