Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
361 FXUS66 KSGX 192049 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 149 PM PDT Wed Jun 19 2024 && .SYNOPSIS... Building upper level ridge in the Southwest US will lead to a warming trend late week and into the weekend. High temperatures this weekend will be as much as 8 to 12 degrees average for the inland valleys onto the lower coastal mountain slopes as well as the deserts. Nights will be warmer over the weekend into early next week for the lower deserts and foothills with a shallow increase in lower level moisture on Saturday. Mid level monsoonal flow will increase from Sunday into early next week. The marine layer will keep coastal areas cooler with areas of night and morning low clouds spreading into portions of the valleys late at night but less extensive. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds have cleared to the coast with lingering clouds along Orange county beaches and patches on San Diego beaches. The large eddy is forecast to dissipate and the marine layer lower tonight but return solid along the coast and portions of inland valleys. Less marine clouds are expected on Thursday and into Friday with warming aloft with the upper heights rising. The warming at the surface is notably on Friday to above average levels of 5 to 10 degrees. A challenge this weekend is a low level surge of moisture and possible some mid level clouds as well. This occurs Saturday for the lower deserts and should shave temperatures down few degrees but inland valleys hotter. The air mass recovers slightly on Sunday and warms again by Monday with high temperatures 6 to 12 degrees above values. Due to the dip on Saturday the southwest offices are not issuing a heat watch yet but the focus is on a prolonged heat wave under the upper ridge and slight drying for next week while monsoon moisture sets up in Arizona. For our inland valleys the hottest days initially are Friday and especially Saturday which would be in moderate heatrisk for heat advisory. A weak eddy will keep a normal marine layer with morning burn off on the coast and less extensive marine clouds this weekend. The heat next week could top at 115F for our lower deserts where 850 mb temperatures hold at 30-32C through at least Thursday and the western edge of this affects our inland valleys at moderate heatrisk. && .AVIATION... 192035Z...Coast/Valleys...Low clouds marine layer begin to spread back inland after 01 to 03Z and spreading 10 to 15 miles inland by Thursday morning. Bases will be lowering tonight near 1000 ft AGL for SAN and SNA with tops to 2000 ft MSL with dissipation of the main coastal eddy. There is a 60 percent chance of cigs below 1000 feet AGL and MVFR visibility for CRQ. For ONT, a 40 percent chance of cigs just below 1000 AGL and MVFR visibility. Morning haze from recent wildfires. Mountains/Deserts...Clear with unrestricted vis through Thursday morning. Local gusts to 20 knots late afternoon and early evening. && .MARINE... No hazardous marine weather conditions are expected through Sunday. && .BEACHES... A southwest swell on Sunday bring long period and slightly increased surf late in the day. && .FIRE WEATHER... Fuels have dried out inland to average levels but winds are trending lighter into the weekend to normal diurnal wind. Areas along and east of I-15, mountains and deserts, have been notably warmer than normal compared the coastal areas that have been running below average past 60 days. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC/FIRE WEATHER...Tardy AVIATION/MARINE...Tardy