Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
706 FXUS66 KSGX 221000 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 300 AM PDT Sat Jun 22 2024 .SYNOPSIS... High pressure building over the Southwest will bring hot weather to the valleys, mountains and deserts through the middle of next week. A shallow marine layer will moderate temperatures near the coast. A surge of monsoon moisture tonight and Sunday will bring higher humidity and a slight chance for showers and thunderstorms. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The summer solstice on Friday, the day with the most daylight, brought with it a hot day. The high was 113 at Palm Springs and 112 at Ocotillo Wells, 97 at the Victorville, and 99 in Johnson Valley in the High Desert. The heat also filtered in the Inland Empire with a high of 95 at San Bernardino and 98 at Hemet. Today will be hotter as the upper ridge over Texas backbuilds westward toward New Mexico and Arizona, raising 850 mb temperatures from 24.5C Friday to 28C today. That will translate to highs near 115 in the Lower Deserts, from 100 to 105 in the High Deserts, and from 98 to 104 in the Inland Empire. A modest surge of mid-level moisture the southeast flow around the upper ridge tonight and Sunday will raise Precipitable Water values to 1.75" in the Lower Deserts, 1.25" in the west of the mountains and 1" in the mountains. A weak shortwave coupled with the heat of the day will generate mid-level lapse rates of 7.7C/km Sunday afternoon and raise CAPE values to 500-600 J/kg. This is when the chances for scattered convection will be greatest. Thunderstorm chances dwindle Sunday night but isolated convection is again possible Monday, mainly over the San Bernardino Mountains and High Deserts. Next week will be hot in the valleys, mountains and deserts with the ridge of high pressure anchored over the Four Corners region. An Excessive Heat Warning is in effect for the deserts through Thursday evening. Coastal areas will be spared the searing heat by a shallow marine layer. On Friday and Saturday the ridge weakens ahead of a Pacific trough that will bring a few degrees of cooling to the region. && .AVIATION... 220900Z...Coast/Valleys...Low clouds increasing in coverage at this hour with bases around 1000 ft MSL and tops to 1400 ft MSL. Inland spread will be restricted to the coastal areas and the western portions of the San Diego County valleys. CIG impacts currently at KSAN and KCRQ. 35-45 percent chance for CIG impacts at KSNA between 13Z and 15Z. Bases could briefly drop below 1000 ft MSL 12Z-15Z. Local VIS 1-3SM on elevated coastal terrain. Clearing to the coast 14Z-16Z. Mountains/Deserts...Clear with unrestricted VIS through today. && .MARINE...Tropical moisture is expected to arrive tonight through Sunday morning. The moisture is enough with a weak disturbance to bring a threat for widely scattered lightning and brief showers tonight through Sunday. See the Marine weather statement for more information. && .BEACHES... There is a slight chance of thunderstorms tonight through Sunday which could produce cloud-to-ground/cloud-to-water lightning strikes. Chances of a lightning strike near any particular beach are currently 20 percent or less tonight and Sunday. Rain showers will generally be brief and light to moderate. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory from 10 AM this morning to 8 PM PDT Sunday for Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Valleys. Heat Advisory from 10 AM this morning to 8 PM PDT this evening for Riverside County Mountains-San Bernardino County Mountains-San Diego County Mountains. Excessive Heat Warning from 10 AM this morning to 8 PM PDT Thursday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...Moede AVIATION/MARINE/BEACHES...PG