Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
040 FXUS66 KSGX 061610 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 910 AM PDT Sat Jul 6 2024 .SYNOPSIS... An area of high pressure will dominate the weather pattern over the next week, leading to hot conditions inland. The high is expected to weaken slightly by Monday, but restrengthen by Tuesday and Wednesday bringing minimal relief. This weather system will keep the marine layer quite steady, with moderated temperatures near the coast and night/morning low clouds each day with morning fog across elevated terrain. The ridge of high pressure will push further east by later next week, allowing the potential for monsoonal moisture to reach the mountains and deserts with continued warm conditions across SoCal. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The 12z Miramar sounding showed a nearly 20C (!) inversion based just below 1100 feet, and an 850 mb temperature near 32C, around 2C degrees warmer than Friday morning. Low clouds extend up to 25 miles inland but are starting to erode across the San Diego County Valleys. Most areas should clear out by late morning or early afternoon, though some beach locations could see passing clouds through the day. It will be another very hot day across inland areas, with highs running 5-15 degrees above seasonal averages. Moderate to major heat risk is likely in the valleys and mountains, with extreme heat risk in the deserts. Limit time outdoors or in spaces without air conditioning and make sure to remain hydrated. Previous Discussion (Issued 217 AM PDT Sat Jul 6 2024)... The area of high pressure over California responsible for this will continue to impact the area today, though most areas will see temperatures a couple degrees cooler. 850 mb temps will still be elevated but slightly less overall. Low level moisture surges will impact lower desert regions each morning, leading to very hot and muggy conditions. Risk of heat impacts will be high to extreme yet again today and Sunday from the foothills, into the mountains and over the deserts. Long duration outdoor recreation is highly discouraged, since temperatures will soar very quickly each morning and stay quite warm overnight. Make sure to drink plenty of fluids and check on those susceptible to the heat. Slight cooling will be seen for valleys and southern mountain areas as onshore flow increases on Sunday, though still near 5 to 10 degrees above normal. West winds will pick up near 20-35 MPH (locally 45 MPH) for mountain passes into the deserts by Sunday afternoon and evening. By Monday, the high centered over Northern California will push over Southern California, weakening slightly, though 850 mb temps look to stay similar to Sunday. This may drop temperatures a degree or two by Monday afternoon where most locations from the coastal valleys to the mountains will be in the 80s to near 100 degrees. Ensemble forecast guidance shows the ridge of high pressure amplifying over SoCal into the Great Basin by Tuesday and Wednesday, where the air mass will warm once again. This will bring temperatures back up to levels similar to this weekend, though the deserts will remain hot with highs near 115 to 120 in the lower deserts most days. Confidence in the forecast remains moderate as we head into later next week, mostly due to the placement of this large dome of high pressure. Global ensembles are in fairly good agreement, depicting the high pushing slightly eastward by Thursday through Saturday. If this occurs, southerly flow around the high would pull in moisture into our region, which may be able to give mountains and deserts a shot at showers and thunderstorms. This monsoon signal begins with minor chances by Thursday, increasing some by Friday and Saturday per NBM. Chances remain near 10 percent at this time, so keep an eye on the forecast as we get closer. && .AVIATION... 061555Z...Coast...Low clouds cover coastal areas this morning, with cloud bases 400-800 feet MSL and tops to 1500 feet. Vis reductions 2- 5SM in BR over higher coastal terrain. Scatter out expected now through 17Z, but with areas of low clouds persisting along beaches into this afternoon. Low clouds with similar bases will gradually move ashore after 04Z Sunday. Otherwise, mostly clear skies with unrestricted vis through today. && .MARINE... No hazardous marine conditions are expected through Wednesday. && .BEACHES... A long-period south swell will continue to create elevated surf. The surf will peak today before subsiding on Sunday. Sets of 6-7 feet can be expected on south and southwest-facing beaches, especially in Orange County. Check the Beach Hazards Statement for details. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Sunday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas. Excessive Heat Warning until 9 PM PDT Sunday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Mountains. Excessive Heat Warning until 9 PM PDT this evening for San Diego County Valleys. Heat Advisory until 9 PM PDT this evening for Orange County Inland Areas-Santa Ana Mountains and Foothills. Excessive Heat Warning until 9 PM PDT Wednesday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC...EA AVIATION/MARINE...Adams