830 FXUS66 KSGX 292044 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 144 PM PDT Sun Oct 29 2023 .SYNOPSIS... Santa Ana winds will peak through the mid-afternoon hours today across the mountains in San Bernardino and Riverside Counties, the Inland Empire and inland Orange County. Slightly weaker winds are anticipated for San Diego County today, but will increase tonight as winds turn more easterly. Warming will occur west of the mountains through Monday, with gradual warming across all of Southern California by midweek. Much drier conditions will accompany these offshore winds as well. Winds weaken by midweek, but prevailing ridging will prolong our warm and dry conditions into next weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Strong Santa Ana winds continue this afternoon in northern areas, especially in the corridor between the Cajon Pass, into the Inland Empire and into the Santa Ana mountains and coastal foothills. Winds have likely peaked already this morning, and will continue with gusts 50 to 65 mph through mid afternoon. Slight weakening of the winds is expected later this afternoon through this evening, before winds kick up again overnight. After sunrise Monday morning, winds will gradually decrease through much of the day Monday, but still remain elevated with gusts 45 to 60 mph. Due to the north/northeasterly component of the wind, San Diego County will mostly be spared from the stronger winds today. Once the mid level winds shift to more easterly tonight, expect winds to increase in the San Diego County mountains, but winds will not be as strong as they are today in the northern areas. Wind gusts generally 40 to 50 mph are expected in the San Diego County mountains and into the coastal foothills beginning tonight and continuing through Tuesday morning. Some isolated gusts to 60 mph could occur tonight into Monday morning in the windiest passes and canyons of the San Diego County mountains. Relative humidity values have tanked this afternoon, with widespread relative humidity less than 15 percent away from the immediate coast. Some inland spots are as low as 5 percent this afternoon. Similarly low humidity values are expected each afternoon through Wednesday. Very poor humidity recovery is expected each night through Wednesday, with humidity values only reaching up to 30 percent. Very strong winds combined with extremely low relative humidity will lead to critical fire weather conditions today and on Monday, with near-critical conditions on Tuesday and Wednesday as winds begin to weaken. However, live fuel moistures remain above normal from Hilary and previous rain events from earlier this year, so no fire weather products are anticipated at this time. Warmer conditions will occur west of the mountains today, with highs 8-12 degrees warmer than Saturday across Orange County and the San Diego County coast and valleys. Noticeable cooling is expected in the mountains and deserts from cold air advection behind the departing low. Highs on Monday will warm 3-8 degrees region-wide, with continued slow warming on Tuesday. With dry air in place through much of the next week, overnight lows will be quite chilly, especially in the mountains and High Desert for the next couple of nights. Lows in the High Desert will drop into the low 30s tonight as winds calm. This will allow for frost formation, so a Frost Advisory has been issued for the High Desert from midnight tonight through 8 AM Monday morning. Similarly cold lows are possible again Monday night into Tuesday morning in the High Desert. Pressure gradients will remain offshore through much of the upcoming week. Mid-range ensemble cluster analysis shows a high likelihood of persistent ridging over Southern California. This will lead to a fairly stagnant pattern with little day-to-day change in temperature across inland areas Thursday into next weekend. Flow may turn more neutral sometime next weekend allowing the marine layer to rebuild slightly, but no significant changes in the pattern are apparent through the next week and a half. && .AVIATION... 292030Z...Mostly clear skies will prevail across the region through Mon with mostly unrestricted vis except for isolated 3-5 mile vis in blowing dust this afternoon. Santa Ana winds will continue through Mon. Through 23Z today, areas of winds 20-30 kt with gusts of 40-55 kt will occur in the mountains, foothills and valleys, locally 65 kt over ridges, through wind-prone canyons, and below mountain passes. Strong UDDFS and LLWS will occur over and south/west of the mountains. Winds will decrease by 5-10 kt in most areas tonight and Mon. && .MARINE... Northeast winds with local gusts 20-25 knots, especially near shore and between Camp Pendleton/Oceanside and San Clemente Island will occur through Monday morning with local short-period seas to 5 feet. Otherwise, no hazardous marine conditions are expected through Friday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...High Wind Warning until 10 PM PDT Monday for Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Gorgonio Pass Near Banning- Santa Ana Mountains and Foothills. Wind Advisory from 2 AM Monday to 5 PM PDT Wednesday for San Diego County Mountains-San Diego County Valleys. Frost Advisory from midnight tonight to 8 AM PDT Monday for Apple and Lucerne Valleys. Wind Advisory until 10 PM PDT Monday for Orange County Coastal Areas. PZ...None. && $$ PUBLIC...Connolly AVIATION/MARINE...Maxwell