February 22, 2021 – Warm and dry weather continues early this week with cooler weather expected the second half of the week. Breezy northerly winds thru mid-week, strongest on Wednesday.
Occasional high clouds are spilling over the eastern Pacific ridge into NorCal early this morning. Enough northeast surface pressure gradient remains over the area for locally breezy to windy conditions. Northerly gusts of 15-25 mph are present across the northern half of the Sacramento Valley, and along the western edge of the valley. Northeast gusts of 30-40 mph are occurring across the higher elevations of the northern Sierra Nevada, and near some of the southwest facing canyons over the foothills.
The region will remain downstream of strong ridging centered off the West Coast today. Highs will be milder than Sunday with readings in the mid to upper 70s possible across the northern Sacramento Valley (likely just shy of daily records which are around 80). Pressure gradients will gradually relax this morning with lighter winds expected in the afternoon.
Pattern begins to change Tuesday as short-waves move through the PacNW weakening high pressure over NorCal. A series of progressively stronger dry cold fronts will move through beginning Tuesday leading to a return of breezier north winds in its wake.
The first front will bring cooling the northern half of the forecast area Tuesday, but will largely wash out as it moves south. Highs Tuesday will be up slightly compared to today in the Sacramento and Stockton region, and will be close to daily records.
A second dry front moves south Tuesday night, followed quickly by a third stronger front on Wednesday. This will bring considerably cooler temperatures to the region on Wednesday along with gusty northerly winds.
The MFR-SAC gradient is forecast to climb to around 13 mbs with increasing upper support, and EC EFI point toward strongest winds occurring over the Sacramento Valley (potential for gusts of 40-50 mph). Wind advisory will likely need to be issued if the forecast continues to trend in this direction.
Lighter winds and milder temperatures are forecast to return Thursday as ridging briefly rebuilds.
Extended discussion (Friday through Monday)
We will be on the eastern edge of a high amplitude ridge for the start of the extended period. This will keep quiet weather in place for Friday. Late Friday into Saturday a trough will dig down the BC coast and track through the PacNW into the Great Basin. This may kick off an isolated shower over the high Sierra Saturday but this trough will have a tough time pulling in any moisture given its placement.
The bigger impact will be increased northerly and easterly flow during the day Saturday. Short wave ridging builds in for Sunday. Ensemble solutions then diverge greatly as we head into early next week. The majority of the members (~80%) support a trough over the west but are having trouble with the placement.
At this point enough confidence to say rain and snow chances return but little to no details at this point. Highs will start out above average but will return to near average Saturday and will remain there into early next week.