Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
341 FXUS66 KSGX 010441 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 941 PM PDT Sun Jun 30 2024 .SYNOPSIS... Hot conditions are expected this week for inland areas, with the hottest conditions in the deserts. Highs in the deserts will be 10 to 15 degrees above normal Thursday through Sunday with highs in the valleys 6 to 12 degrees above average Friday and Saturday. The marine layer will be shallow, where areas near the beaches and adjacent valleys will see night and morning low clouds most days. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low cloud coverage is expected along much of the coast tonight and into portions of the western valleys. Low clouds are expected to clear fairly quickly Monday morning, leaving plenty of sunshine across the area. Highs on Monday will be a few degrees cooler than today from the coast to the deserts with an upper level trough moving east across the Great Basin. Warming is expected in the deserts by Tuesday as influence from the low weakens. A strong high pressure system aloft will slowly move towards California from the Pacific through the work week. The high will eventually park itself over California by the weekend, causing high temperatures to soar to well above seasonal normals for inland locations. Global ensemble guidance is showing the high pressure system lingering over the West Coast into next week, although there is some uncertainty in the details regarding the strength and placement of the high starting Saturday. Even with that uncertainty, there is enough agreement amongst the guidance to indicate that the high will stay close enough to continue this heat wave into at least the beginning of next week. Moderate to high heat risk for inland areas Wednesday through at least Sunday will lead to elevated impacts for those outdoors. Make sure to take frequent breaks if working outside, drink plenty of water, and be safe and smart while doing outdoor recreation. From previous discussion issued at 2 PM June 30... By Wednesday, winds will weaken for mountains and deserts, with a shallow marine layer within 20 miles of the coast leading to patchy fog each morning. A large area of high pressure over the Southern States along with an inverted trough off the coast of northern Mexico will help feed elevated moisture into the region, which will lead to a more humid day, especially for the deserts. Confidence on any storm development is still very low at this time, but we will continue to monitor. The aforementioned area of high pressure will grow and expand across the State from the middle to the end of the week. 850mb temps peak across SoCal by Friday and Saturday. Hot temperatures are likely for those away from the coast starting Wednesday into the long holiday weekend. Triple digit heat is likely for much of the week for those along and east of I-15 in the Inland Empire, and certain for all desert regions. Highs near 110 degrees have a 40-70 percent chance of occurrence across the high desert, with 60-80 percent chance of highs 115 or greater for the lower deserts by Friday and Saturday. High temperatures have a moderate to high chance of reaching into the 90s from areas east of I-5 in OC to east of I-15 in SD Co, highest chances on Friday and Saturday. This heat wave will even bring hot temperatures well into the 80s and 90s across the mountains! && .AVIATION... 010430Z...Coast/Valleys...Areas of low clouds will continue to develop within 10 miles of the coast through 08Z Mon and eventually expand up to 20 miles by 12Z Mon. Bases will be 700-1100 ft MSL with tops to 1400 ft MSL. Local VIS 1-3 miles in BR will occur 08Z-16Z Mon in the coastal valleys. Most areas will clear 15Z-17Z Mon with VFR conditions prevailing Mon afternoon. Low clouds will spread inland earlier Mon evening, with coastal airport CIGs beginning 02Z- 06Z Tue, with a slight increase in bases. Mountains/Deserts...Mostly clear skies with unrestricted VIS will prevail through Mon evening. Local west sfc winds with gusts 25-35 kt will continue through 08Z Mon, then again after 23Z Mon, on the desert slopes and through San Gorgonio Pass. && .MARINE... No hazardous marine conditions are expected through Friday. && .BEACHES... A long-period swell of 2-3 feet from 190 degrees with a period of 16- 18 seconds will arrive at SoCal beaches as early as Wednesday morning, peak Friday and gradually subside next Sunday. This may lead to elevated surf with breaking wave heights of 6-7 feet, mainly on exposed south and southwest-facing beaches in Orange County. Rip current risks will be high the second half of this week. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning from 11 AM Tuesday to 5 AM PDT Monday for Apple and Lucerne Valleys. Excessive Heat Warning until 5 AM PDT Monday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...CO/APR AVIATION/MARINE/BEACHES...Maxwell