BASIC PATTERN:
Large Scale Pattern –
- Long wave ridge of high pressure has been with us for a long time. It resulted in an almost bone-dry January in Mendocino and Humboldt Co’s, which has continued the first week of Feb. We are starting to see a gradual shift to a slightly wetter pattern beginning in the last week of Feb and early to mid-March.
- February’s final 10 days: Continued drier than normal, with near normal temperatures overall. Showery periods are: Feb 21, Feb 27-28-1 Mar, 4or 5 Mar, 9-12 Mar, and 14-18 Mar.
- March: A turn to cooler than normal occurs in N California, and normal or a little warmer than normal in S California. Mar is currently forecasted wetter than normal due to cooler or cold days during trough periods in N and Northcentral California. About normal frost risk in S California (SOCAL), including San Diego/Orange/W Riverside Co’s before and after passages of fronts, associated clouds and perhaps a stray rain shower.
- Recurrent fronts, most without rains, from the North Pacific will tend to support near-normal frost/freeze events for the late winter: Early to mid-Mar, including SOCAL citrus and avocado regions. Input of moisture from clouds or showers into Central and SOCAL agricultural areas will be spotty/questionable at end of Feb, and slightly better chance for rains in mid Mar.
- Medium range forecast models have performed poorly during this extremely dry late winter period. The stationary IVTinit pattern (related to sea surface temperature anomalies, has kept troughing in the central North Pacific, and high pressure close enough to the California coast to block storms from arriving, or else cause persistent weakness in approaching systems. The snow cover and cold forcing to our east, plus the mid Pacific troughing is indeed a dry pattern that is difficult to break.
FORECASTS FOR CALIFORNIA
Precipitation Trend: The main dates of precipitation are: Feb 21, Mar 1-2, Mar 4-5, 9-12, 14-18.
Forecast for Northern and Central California:
NORCAL Rains: Feb 21 (light shwrs), Mar 1-2, 4-5, 9-12 and 14-18.
CENTRAL CALIF Rains: Feb 21 (light shwrs), 2, 4-5, 10-12 and 15-18.
WARM SPELLS: Feb 24-26 and Mar 7-8.
COLD SPELLS: Feb 21-22, 27, Mar 1-5 and 9-18.
FRONTS WITH RAINS: Feb 21, Mar 1, 4, 9 and 14.
FROST AND FREEZE: Feb 17-20, 22-24, Mar 3, 6-8, 13 and 19-20.
Forecast for S California:
SOCAL RAINS: Feb 21, Mar 5, 11-12 and 16-18.
SOCAL WARM SPELLS: Feb 17-20, 24-27, Mar 7-8 and 20-21.
SOCAL COOL OR COLD SPELLS: Feb 21-22, Mar 5-6, 11-13 and 16-19.
FROST PERIODS: Feb 17-20, 23-24, Mar 6-8, 13-14 and 19.
FRONTS WITH RAINS: Feb 21, Mar 5, 11, and 16.
Sierra Nevada:
Dates of mountain rains and snows are: Feb 21-22, 27-28, Mar 2-5, Mar 10-12 and 15-18.
----------
The listing of dates normally included for hot and cold spells, and precipitation are based on our CFSDaily and CFSDailyAI forecast products, and present expected trends in precipitation and temperature (CFSDailyAI) to 4km. Our system gives some consideration of 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.
----------
Southern California Deserts Outlook for Feb 10-Mar 7, 2022:
Highlights: The CFSv2 model shows a return to near or a little above normal temperatures for SE California deserts in Feb, and about normal temperature but no clear trend for precipitation for SOCAL deserts in March. Best chances for freezes in Feb and Mar are in the dry cool airmasses behind cold fronts, after dry downslope winds diminish or subside. The CFSv2 model is suggesting a slow trend towards warmer than normal days in Mar. If this occurs, then frosts may become less frequent than normal. We note that NORCAL is colder than normal per CFSv2 in Mar, while SOCAL is warmer than normal per CFSv2 guidance.
Looking Ahead – Long Range Outlook
Mar 14 – May 7, 2022 N and Central California: Near or a little below normal temperatures for Mar 2022. Slightly below normal temperatures for Apr 2022. Near normal rainfall in the Delta and Northern California.
Mar 14 – May 7, 2022 - For SOCAL mountains westward to coast: Near normal temperature for Mar, above normal temperature for Apr to early May. Drier than normal in Mar, but near normal rainfall for April (a month of usually meager rainfall).
Additional Comments:
CFSv2 monthly guidance suggests troughs coming into California and the Sierra Nevada to Great Basin at times in Mar, although we are emerging from frost season. Again, the best chance of frost/freeze will be following dry cold frontal passages and after dry downslope winds subside. The CFSv2 suggests a possible early exit from frost season. However, the dry airmasses and N flow regimes continue at least some residual risk of frost into early spring.
In summary, after the mostly dry Feb, there is a possible up-tick of rains in late Feb and in early to mid March (NORCAL). Some of those showers may sneak into SOCAL on a few occasions. Otherwise, a drier than normal rainy season, overall, is likely, with some seriously low reservoir levels at the beginning in May-June of the long dry hot summer season.
(Terms and Definitions Used In This Weather Outlook)
Alan Fox & Zane Stephens...Fox Weather, LLC
Copyright © 2022, Fox Weather, LLC, Used by permission.