Rain and snow showers are expected to increase in coverage across the mountains and deserts after midnight through Saturday morning. Snow levels will be near 6500 ft. Shower activity will decrease by mid-Saturday morning, with dry conditions expected to return by Sunday. Periods of gusty northeast to east winds will continue overnight into Saturday. A gradual warming is expected for next week, with high temperatures returning to above normal by the middle of the week. A weak Santa Ana is possible sometime mid- week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Current radar at 9 PM was showing a swath of precipitation just south of the border, with an isolated light shower or two moving across San Diego County. The forecast is still on track for wrap around moisture from an upper level low moving into northern Baja tonight. High resolution guidance has most of the shower activity developing for the mountains and deserts after midnight. Rain and snow shower activity is expected to become more isolated by mid- Saturday morning. Light showers may continue into Saturday afternoon as the low slowly moves east. Dry conditions are expected to return by Sunday.
Northeast to easterly winds have developed on the coastal mountain slopes and locally into the valleys. Peak gusts as of 9 PM have mainly been in the 35 to 45 mph range, with a few isolated gusts to 50 mph in wind prone locations. These winds will continue into Saturday, slowly weakening and becoming more isolated into Sunday.
From previous discussion issued 2 PM November 21,
The upper low over the California Bight will be pulled southward into northern Baja tonight into Saturday. As this occurs, wrap around precipitation is set to fill back into the area this evening into the overnight hours, favoring the deserts and southern/eastern mountain slopes, especially in San Diego County. This precipitation will generally be light, with rates up to 0.1-0.2"/hr though localized enhancements, particularly along the San Diego County desert mountain slopes, are possible. Additional rainfall totals from this wrap around will be 0.2" or less for the coasts/valleys, 0.75-1" in the mountains (though eastern slopes could see additional totals closer to 1.5-1.75"), and 0.25-0.5" in the deserts. Snow levels remain near 6500ft through tonight but gradually rise to ~7000ft Saturday afternoon. Additional snowfall above 6500ft through Saturday morning range from 2-5", with locally up to 9" on eastern mountain slopes. Snowfall rates could be 1-1.5"/hr at times and given the expected additional snowfall, the Winter Storm Warning has been extended through 10 AM Saturday for mountain elevations in San Bernardino County and Riverside County greater than 6500ft.
The wrap around precipitation eventually tapers off by Saturday afternoon as the upper low begins to lift northeastward and dry northwesterly flow aloft returns for Sunday into Monday. Temperatures slowly respond with a subtle warming trend that returns afternoon highs to seasonable norms by Monday/Tuesday. Ensembles are consistent with a trough digging from the Pacific Northwest through the Great Basin, aiding to strengthen to the offshore pressure gradient Tuesday into Wednesday. Currently there is about a 40% chance of a weak to moderate Santa Ana event mid-next week, likely peaking around Wednesday. Between the offshore winds and an upper ridge peaking Thursday, temperatures warm to 5-10 degrees above normal for Wednesday into Thursday.
Looking into the far extended, ensembles continue to hint on another storm system late next week that could bring another round of rain. Significant uncertainty remains in the timing and track of this next trough, so it's not something to get too excited about just yet.
220400z, Coasts/Valleys, Light rain and associated cig/vis have become more isolated with sct/few clouds between 5,000 to 7,000 ft MSL. Light rain will increase in coverage again mainly over San Diego County this evening through 12Z Saturday. East to northeast winds gusting 25-35 knots in the coastal foothills and locally into inland valleys through 00z Sunday.
Deserts/Mtns, BKN-OVC low clouds 5000-8000 ft MSL currently. SHRA will become more persistent and widespread in the low deserts after 09z with MVFR cig/vis reductions at times. SCT FG/SHRA/SN in the mtns through Saturday morning, especially along the eastern slopes, where precip will be favored. Conditions slowly improving after 18Z everywhere with any precip becoming more SCT and intermittent.
No hazardous marine conditions are expected through Wednesday.
Ca, Winter Storm Warning until 10 AM PST Saturday for Riverside County Mountains-San Bernardino County Mountains.
PZ, None.
