BASIC PATTERN:
Large Scale Pattern –
- The westerlies have drifted now to near their wintertime position across the Pacific. Despite the atmospheric river system now expected into central California on 31 Dec, there will still be risk of significant interruptions to the usual winter rain pattern during the last parts of January and first part of February 2023. In the broad picture, there is recurrence of a wet pattern occurring 31 Dec, Jan 2,4,5,6 and 8 Jan, 11-15 Jan, and atmospheric river conditions possible within 17-24 Jan.
- We note that the sea surface temperature anomalies (from the NOAA/NESDIS Coral Reef Watch Program) continue the weak El Nino contribution. However, El Nino may be waning at this point, focusing east of 120-115W. Its Contribution will be to induce a tendency for troughing in Arizona, The Rockies, and Central US plains areas. As this occurs, we would tend to see a return of cold periods in the Great Basin, snows in the Rockies, and return of dry spells with freezes for the California Central Coast at times in Feb as well as late Jan.
- Precipitation Trend: Rains 31 Dec with mountain snows followed by a cold front with lower snow levels 1 Jan. More rains follow quickly on Jan 2,4,5-6, showers on 8th. Rains are possible 11-15th, and atmospheric river conditions are possible part of the period 17-24th. A well defined dry period appears to develop during about 25th through the first week of Feb.
- SOCAL precipitation trend for the first period of 30 days: Rains/showers on 28-31 Dec - 1 Jan. The first half of Jan 2023 appears to be drier than normal for SOCAL, despite the rains in N and Central California.
- In Feb 2023, from NMME and CFSv2 models, there is a tendency to continue below normal precipitation, except for possibly some rains and Sierra snows during 10-19 Feb, and 27 Feb – 2 Mar.
- March 2023 looks currently (from NMME Model) colder than normal, but with a chance for above normal snowfall for the NORCAL mountains, including N Sierras, NORCAL coastal mountains, the NE Plateau, and N Sierras.
FORECASTS FOR CALIFORNIA
Forecast for Northern and Central California:
Norcal PRECIPITATION: Dec 27, 29-Jan 2, Jan 4-6, 7-9, 11-14, 17-25 and 31.
Norcal MILD SPELLS: Jan 16 and 27-30.
Norcal COOL SPELLS: Dec 27-Jan 4, Jan 5-14, 27-26 and 31.
Norcal WINDS (dry cold winds): Dec 31-Jan 3, Jan 7-9, 13-14 20-21 and 24-25.
Norcal FROSTS/FREEZES: Jan 10, 15-16 and 26-28.
Central Calif PRECIPITATION: Dec 27, 29-31, Jan 2, 4, 5-6, 12-14 and 18-25.
Central Calif MILD SPELLS: Jan 8-11 and 16-17.
Central Calif COOL SPELLS: Dec 27-Jan 6, 12-15 and 18-26.
Central Calif DRY COLD WINDS/FREEZE RISK: Jan 7-8, 15-16 and 26-28.
Forecast for Southern California:
SOCAL RAINS: Dec 27-28, 31-Jan 1, 2,4, 5, 6, 21-22 and 24-25.
SOCAL MILD TO WARM SPELLS: Jan 9-11, 16-20 and 27-31.
SOCAL COOL OR COLD SPELLS: Jan 1-5, 6-7 and 21-25.
SOCAL FROSTS/FREEZES: Jan 4, 7-8 and 21-23.
SOCAL SANTA ANAS: Dec 30 (light), Jan 1, 7, 23 and 26-28.
Forecast for Central Sierra Nevada:
Central Sierra Nevada Precipitation: Dates of rain or snow: Dec 27-31, Jan 2-5, 6-7, 12-15, 17-26 and 31.
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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 (CFSDailyAI) to 4km. 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 December 31 - January 31, 2023
Highlights: Dry through Dec 26. Possibly a showery windy cold front about 28-31 Dec – New Years Day. As usual in late Dec-early Jan, watch for frosts and freezes as skies clear out behind fronts.
Looking Ahead – Long Range Outlook - January 31 - February 28, 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. Watch for above normal risk of dry downslope winds in late Jan – Feb 2023. Below normal precipitation in Jan 2023 from the CFSv2 and NMME in most areas of N and Central California.
For SOCAL mountains westward to coast: This period currently appears seasonably cold with above normal risk of frost and freeze. Precipitation in mountains and deserts..below normal for most areas except near normal in some mountain spots. Watch for above normal frequency of Santa Anas, warm days but abnormally cold nights. Although cutoff lows may develop on occasion to bring rains to Southern California, the supply of surface and ground water will be heavily dependent on strategic planning of water storage in Northern California and Sierras with the expected rains in NORCAL, and snows in Sierras and Siskiyou’s. We expect a return to abnormally dry conditions in SOCAL and at the central coast in mid Jan onward, with recurrent Santa Anas. Dry also in Feb, with recurrent frosts/freezes. The CFSV2 Model at this time shows a wet and cold March for California. However, the challenge continues to plan usage of whatever snow water equivalent (SWE) we have. The season for Atmospheric Rivers to beneficially add to lakes and rivers this year has been Dec, and it appears we see some more this week, and in 17-24 Jan. The rains and snows in Dec, followed by seasonably cold temperatures may help to maintain some of the Sierra snowpack. March appears to be colder than normal but with cold spells. The unusually cold and dry events (frost-freeze) in Feb for Central California will affect challenge to the water supply during the spring frost protection season in NW and Central California bloom periods.
(Terms and Definitions Used In This Weather Outlook)
Alan Fox & Zane Stephens...Fox Weather, LLC
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