Dry and warm weather with increasing high clouds continues into Tuesday with gusty Santa Ana winds across the mountains and valleys. A low pressure system will bring periods of showers for New Year's Eve and New Year's Day, followed by additional mostly light showers Friday into early next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Evening update, Gusty Santa Ana winds continue this evening across the foothills and valleys. Winds have weakened somewhat, with the strongest gusts currently around 50 mph, but should strengthen again overnight for areas more prone to easterly winds. The Wind Advisories remain in effect through 1 PM Tuesday. Otherwise the massive band of cirrocumulus clouds that brought a stunning sunset across part of the region will progress northward overnight, perhaps producing a lovely sunrise as well if cloud cover doesn't get too thick.
New Aviation section updated for the 06z TAF package.
Previous discussion, With an upper-level high pressure ridge to the north and a closed upper low about 400 miles southwest of San Diego retrograding to the southwest, dry and warm weather will continue through Tuesday. Periods of gusty Santa Ana winds will also continue through Tuesday. Northeast to east winds will continue to gust 45-55 mph with locally higher gusts in winds-prone areas. Tuesday will likely be the warmest day with temperatures in the 70s to near 80 west of the mtns. Most areas will be near to as much as 11 degrees above seasonal averages. The temperature forecast for Tuesday may be complicated by high clouds moving in from the southwest and reducing daytime solar heating but the increasing heights and thicknesses will tend to raise temperatures.
BY Tuesday, the retrograding upper-level closed low off the coast will merge with the closed low about 1200 miles southwest of San Diego. By Wednesday this new low will begin to move northeast toward SoCal as a low pressure system moves southward out of the Gulf of AK. These systems will bring us periods of rain/showers from late Wed through the weekend. This will likely occur in two distinct phases. The first phase will be the low to the southwest ejecting to the northeast and becoming an open wave over SoCal on Thu. During this phase, relatively warm, moist air from the tropics will result in widespread rain/showers before a dynamic ridge moves over the region on Friday. This ridge could bring a break in the precipitation until the low from the Gulf of AK arrives with colder air and more rain/showers for Sat through Monday. Snow levels will remain above 8,000 ft through Friday then fall to around 7,500 ft on Sat and 6,500 ft on Sunday.
Precip amounts will be greatest in the northern areas (Orange and San Bernardino Counties) and less in southern San Diego County. Current rainfall estimates are for totals of 0.9"-1.9" in the coastal areas, 1.1"-1.6" in the inland valleys, 0.1"-0.6" in the low deserts, 0.1"-0.6" in the high desert, 1.1"-2" in the San Diego and Riverside County mtns and 1.5"-5.0" in the San Bernardino Mountains. Most of the precip will be concentrated along the coastal slopes of the San Bernardino Mountains west of the Cajon Pass. The snow level will remain above 8,000 ft through Friday before lowering to around 6,500 ft on Saturday. Most of the precipitation will likely fall before next weekend so snowfall amounts at resort levels and below will be limited.
300600z, VFR conditions through the TAF period with increasing coverage of BKN-OVC high clouds AOA 20,000ft. Gusty offshore winds have largely relaxed across the region, with localized gusts near 20- 30 kts possible in the mountain passes and coastal slopes overnight. Instances of LLWS remains possible as surface gusts have waned, though winds aloft continue to decrease through 09z Tuesday as well. 20-30 kt winds prevail for the mountain passes and coastal mountain slopes through Tuesday afternoon, but will be more confined to these typical locations compared to today. Elevated offshore winds cease between 00-06z Wednesday.
No hazardous marine weather conditions expected through Saturday.
Ca, Wind Advisory until 1 PM PST Tuesday for San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.
PZ, None.
