BASIC PATTERN:
Large Scale Pattern –
- We note that the sea surface temperature anomalies and IVTinit continue a warm moist pattern across the Pacific from 170W to 130W…30-35N. There is some support now for troughing from the N California coast west and WSW-ward. Beyond that statement, the pattern is not strong enough to look encouraging for a return to wet conditions for the end of winter in California.
- The NMME monthly outlook for precipitation suggests a return to near or a little above normal rainfall for northern California, Mendocino Co north, and in the Sierras from about Butte Plumas Co’s north. An atmospheric river (AR) is a possibility for the period 28 Feb – 4 Mar in NORCAL mountains. A late season AR would really be nice, but a series of them during March is more in the realm of wishful thinking than in well established trends at this time. Southcentral and Southern California from San Luis Obispo County south appear dry, and there does not appear much hope for a return to wet conditions.
- Precipitation Trend: Rain dates in last 10 days of Feb and most of March: Feb 18-19, 25-28, Mar 1-5, Mar 7-8, Mar 12-17, Mar 21-22.
- For the last 10 days of Feb and through Mar: below normal temperatures in all of California and the Pacific Northwest states from NMME and CFSv2 models. Above normal precipitation occurs in Humboldt-Del Norte Co’s of NW California, and the northern mountains area (Siskiyou’s), and N Sierras. Mostly drier than normal conditions are indicated for S California, but with some surprises, due to a persistent or recurrent cyclogenetic zone near SOCAL and far S portions.
- From CFSv2, precipitation anomaly drifts persistently below normal in Mar and Apr, but recovers to near normal in May (which does not mean much because May is a normally dry month. Even if precipitation returns to a little above normal in the Sierras for May, these ‘end of season’ rains lack the volume that we need to counteract the most recent periods of dryness which are made over multiple seasons.
FORECASTS FOR CALIFORNIA
Forecast for Northern and Central California:
Norcal PRECIPITATION: Feb 18-19, 22-28, Mar 1-2, 4-5, 7-8, 12-16 & 21-22.
Norcal MILD SPELLS: Mar 10-11, 18-20 and 24-25.
Norcal COOL SPELLS: Feb 17-28, Mar 1-8, 12-16 and 21-23.
Norcal FROSTS/FREEZES: Feb 20-21, Mar 3, 6, 9-11, 17-18 and 23-24.
Central Calif PRECIPITATION: Feb 18-19, 23-26, 28, Mar 2, 4-5, 8 & 12-16.
Central Calif MILD SPELLS: Mar 7, 10-11 and 18-21.
Central Calif COOL SPELLS: Feb 18-28 (very cold 22-25th), 28-Mar 1, 4-5, 8-9 & 12-17.
Central Calif DRY COLD WINDS/FREEZE RISK: Feb 20-22, 27, Mar 1, 3, 6-7, 9-10 & 17.
Forecast for Southern California:
SOCAL RAINS: Feb 24-26, 28, Mar 4-5 & 13-17.
SOCAL MILD TO WARM SPELLS: Mar 7-10, 12-13 and 18-20.
SOCAL COOL OR COLD SPELLS: Feb 24-28, Mar 4-6 and 13-18.
SOCAL FROSTS/FREEZES: Feb 27, Mar 1-2, 6-7, 10-11 and 18-19.
SOCAL SANTA ANAS: Feb 15-16, Feb 26-27, Mar 6-7 & 17-19.
Note that we are getting out of the season for Santa Anas, and will see more of the thermal troughs over the interior valleys and SOCAL deserts during April and May. In May the thermal forcing for strong and persistent coastal onshore flow will be near the seasonal maximum, with the sea surface still cold, while inland temperatures experience the seasonal warmup.
Forecast for Central Sierra Nevada:
Central Sierra Nevada Precipitation: Dates of rain or snow: Feb 24-26, 28, Mar 4-5 & 13-17.
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The listings of dates normally included for hot and cold spells, and precipitation are very approximate. They are based on our CFSDaily and CFSDailyAI products; and present expected trends in precipitation and temperature (FoxCFSDailyAI) to 5km. Our system gives some consideration to terrain and coastal influence. We consider the CFSv2 as one of the better ways to represent basic weather down in the sub-monthly time scale beyond the 15 –day GFS or monthly maps from CFSv2 or NMME.
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Southern California Deserts Outlook for April and May 2023
Highlights:Generally below normal rainfall, or possibly near normal in a few spots is about the best we can expect at late point in the season for SOCAL Deserts.
Looking Ahead – Long Range Outlook - April 1 - May 31, 2023
NORCAL and Central California coastal valleys, and Central Valley: In general, NMME has been appearing a little drier than the CFSv2 for California as a whole. Both NMME and CFSv2 select a warmer than normal period during the first half of Apr for northern and central California.
For SOCAL mountains westward to coast: This period currently appears about normal for temperature in Apr for SOCAL even though Northern California slightly cooler than normal for early Apr.
Precipitation in mountains and deserts: Below normal for most areas except near normal in some mountain spots. Watch for some warm days in Apr, but warm days counterbalanced with colder than normal nights for a while in April for SOCAL.
(Terms and Definitions Used In This Weather Outlook)
Alan Fox & Zane Stephens...Fox Weather, LLC
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