Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
185 FXUS66 KSGX 162021 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 121 PM PDT Tue Jul 16 2024 .SYNOPSIS... Seasonal weather will continue this week with only small day to day variations. There is a slight chance of thunderstorms, mainly in the mountains in the afternoons. Coastal low clouds and fog will continue to reach into western valleys each night and morning. Temperatures will climb well above normal heading into the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Monsoon moisture has taken a step backward today, and the morning sounding showed a capping inversion at about 19,000 feet. Both factors have led to cumulus struggling to grow into thunderstorms yet as of 1 pm. We still expect isolated stuff through 5 pm and only over the mountains. A high pressure ridge over the West will strengthen a little each day Wednesday into Saturday. That will bring a modest warming trend taking near normal high temperatures Wednesday to 5-10 degrees above normal over the weekend. That will mean going above 104 in parts of the Inland Empire and above 114 in parts of the lower desert. One caveat to watch for is how much if any low level moisture seeps into the low desert each morning, moisture that would literally dampen any temperature rise. The latest GEFS ensemble really goes crazy with this idea, grossly underforecasting desert temps. But it really doesn`t matter: the heat risk will be high whether the temp gets to a dry, scorching 118 or a humid, sweltering 108. With the high over the West strengthening, the marine layer will get suppressed slightly and low clouds should not make it into inland valleys anymore for a while. But the warm air mass and strength of the high will keep the marine inversion nice and strong. No, the low clouds aren`t going anywhere, just backing off a step. The monsoon moisture backs off a little more Wednesday, but a subtle resurgence arrives Thursday to increase the chances of thunderstorms, mainly during the afternoon in the mountains. Copy and paste this idea each day for Friday through Monday. Latest guidance has decreased the chances of tstorms over the weekend, but we`re holding on to a slight chance each day. The strong high pressure over the Southwest is also not going anywhere, so it looks like temps will remain well above normal next week. && .AVIATION... 162000Z...Coast/Valleys...Patchy stratus around 1700 ft MSL is lingering along the coast and just offshore, with FEW-SCT cirrus at or above 20000 ft MSL. Otherwise clear with unrestricted VIS this afternoon. Low clouds with similar bases 900-1300 ft MSL reforming and spreading back into coastal areas after 17/02-03Z, generally moving from the south to the north, and then inland 15-20 mi by 17/10-11Z. Locally reduced VIS 3-5 SM in valleys where clouds intersect terrain, most likely 17/10Z-14Z. Clouds clearing out of inland areas 17/14-17Z and out of coastal sites 17/16-18Z. Mountains/Deserts...Low chances for ISO SHRA/TSRA over the mountains and desert slopes this afternoon, dissipating by 17/02Z. CB bases near 12,000 ft MSL with tops to 30,000 ft MSL. Gusty outflow winds and reduced vis in RA VCTY TSRA, though no impacts to TAF sites expected. Otherwise FEW clouds at/above 10,000 ft MSL and unrestricted vis through Wed morning. Moderately breezy winds through San Gorgonio Pass gusting up to 35 kt through this evening. && .MARINE... No hazardous marine conditions are expected through Sunday. && .BEACHES... Long period 3 ft SSW swell (200-210 degrees) will bring elevated surf of 4-6 feet with sets up to 7 feet for south and southwest facing beaches in Orange and San Diego counties. There is a high risk of rip currents at all beaches. A Beach Hazard Statement is in effect through Thursday evening. Swell and surf will begin to lower on Thursday, though the high risk for rip currents will linger into Friday. && .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 Thursday evening for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...None. && $$ PUBLIC...MM AVIATION/MARINE/BEACHES...CSP/SMALL