January 24, 2021
A very cold low is rapidly advancing on central California. The low itself has a rather odd shape as it essentially stretches from British Columbia to southern California. The air mass with this system is extremely cold and, again, will bring snow down to the lower foothills late tonight and Monday. A surface cold front will drive down the valley between midnight and sunrise Monday. A fairly strong surface low will develop over southern Nevada which will begin to increase surface pressure differences between northern California and the Desert Southwest. Gusty winds will move down the valley late tonight and Monday, driving very cold air into central California.
This will lead to our next challenge, and that is subfreezing temperatures Tuesday morning. where skies clear and winds are calm, temperatures early Tuesday morning could drop down to 25 to 26 degrees in wind sheltered, cold, frost pockets while most other locations, again under clear skies, will range from27 to 31. It’s entirely possible that enough upslope clouds will bank up against the valley facing slopes of the Tehachapi Mountains and the Sierra Nevada to result in a protective cloud deck, keeping temperatures in the 30s. Tuesday morning is the only morning of the week that poses a frost/freeze challenge as a milder very wet pattern will begin Tuesday night and Wednesday.
We’ve been discussing this scenario for the past week now for the possibility of strong winds and heavy rain. It is not a very often that a whole week goes by and models hold onto the same ides, but that’s exactly what has occurred. Therefore, my confidence level is high that by Tuesday night, an intense Pacific storm will be located off the southern Oregon/northern California coast. Confidence is also rising that a pineapple connection will occur as the jet stream zips along at 130 knots per hour, sweeping inland perpendicular to the Coast Range and the Sierra Nevada. High resolution models designed to estimate precipitation amounts are suggesting as much as a foot of rain over the Santa Cruz mountains and possibly more than 6 inches of precipitation along the Sierra Nevada from Fresno County north. This translates to tremendous amounts of snow over the higher elevations.
This current storm should drop between .25 and .50 at most locations then from Wednesday through Friday, one to two inches of rain is possible along the east side north of Kern County with lesser amounts elsewhere.
The other element of the Tuesday night storm is the potential for strong winds in the extreme south valley. As always, we’re just talking chances here, but we will see the possibility of gusts exceeding 50 MPH near the base of the Tehachapi and between 30 to 40 MPH along the west side from later Tuesday night through Wednesday.
Forecast: Periods of rain tonight through Monday. A chance of lingering showers in the south valley Monday evening. Otherwise, mostly to partly cloudy Monday night and Tuesday. Increasing cloudiness Tuesday night. rain likely at times Wednesday through Friday, possibly locally heavy at times. A chance of showers Friday night with a continuing risk of showers, mainly from Fresno County north, Saturday through Sunday.
Temperatures: Lows tonight will range in the upper 30s to the lower 40s. Highs Monday will range in the upper 40s to lower 50s. Lows Monday night will chill from the mid 20s to the lower 30s. Highs Tuesday will range in the upper 40s to the lower 50s.
Next update: January 25, 2021/pm