November 12, 2020 – Dry and quiet weather continue today. Rain and snow return Friday with mainly dry conditions over the weekend.
Discussion
We are seeing mostly clear skies and light winds this morning. This is leading to cold conditions across the region and widespread frost is expected for much of the area. We are also seeing some patchy fog mainly in the river valleys from Marysville south. Any patchy fog will lift shortly after daybreak and then we will continue to see quiet conditions for Thursday as short wave ridging pushes to the east. Some high clouds associated with a short wave trough pushing into the PacNW will move over the area throughout the day.
Our weather will become more active on Friday as a trough digs out of the Gulf of Alaska into the PacNW. Warm air advection will develop Thursday night into Friday morning from I-80 north. This will bring light showers mainly over the mountains but some valley showers will still be possible. Widespread precip is expected for the afternoon and evening as the cold front moves through the area. Precip will diminish Friday night with a few lingering showers over the Sierra. Snow levels Thursday night will start out low 4000-5000 feet, locally lower over portions of NE CA but will be rising Friday morning rising to 5500-6500 feet Friday afternoon. Mountain travel on Friday will likely be challenging and you should plan ahead and keep up with forecast if you have mountain travel plans. Breezy southerly winds can also be expected on Friday especially over the higher elevations.
Dry conditions set in for Saturday with less wind. Upper level ridging will be building into the region on Sunday but a short wave pushing into BC will help to bring some warm air advection to northern portions of the area. This should provide enough lift and there should be enough moisture to see a few light showers. Best shower chances will be over the Coastal Range and shower chances will diminish by the afternoon.
High temperatures today will be similar to yesterday to a few degrees warmer. Things will cool off for Friday and we will see highs run as much as 15 below normal but highs rebound back to within a few degrees of normal for the weekend. After this morning we will see warmer overnight lows with them closer to average.
Extended discussion (Monday through Thursday)
Mainly dry weather expected thru early next week as majority of cluster guidance indicates ridging holding over NorCal. Uncertainty increases by mid-week as the ensemble average put NorCal in a more favorable position for precipitation with southwest flow between a trough offshore and ridging to our east. However, some of the clusters do indicate more digging with the upstream offshore trough and stronger ridging remaining over NorCal. We’ll continue to lean toward higher POP’s north of I-80 WED/THU with high snow levels (above 7k ft).