October 12, 2020 – High pressure continues to build in over the area, which will lead to a warming and drying trend for the week. Periods of breezy north winds will be possible throughout the week, strongest on Wednesday, leading to elevated fire weather concerns.
Discussion
Overall we are going to see quiet weather this week across NorCal as upper level ridging will influence our weather. Short wave troughs will work through the PacNW for the first half of the week and that will keep the ridge more flat over us. It will also bring some mid to high level clouds over the northern part of the area at times.
A bit stronger short wave will push out the PacNW and deepen over the northern Rockies on Wednesday as the ridge begins to strengthen over the Pacific. This is going to bring an increased surface gradient over us for Wednesday. Currently the SAC to MFR gradient is looking to be 10-13 mb which would likely result in northerly wind gusts 30-35 mph across the Valley.
As we head into Wednesday night that gradient will transition from a north to south gradient to a east to west gradient with gusty winds expected over the Sierra and foothills. Low humidity will accompany these winds and that will lead in increased fire weather concerns Wednesday into Thursday.
Northerly flow will become weaker on Thursday as the trough pushes off to the east and upper level ridging really begins to build into NorCal. Our temperatures will continue to warm a few degrees each day with the warmest days expected Wednesday and Thursday where highs will be 10-15 above average.
Extended Discussion (Friday through Monday)
EPAC and Desert SW highs extend over interior NorCal Friday into the weekend resulting in dry weather with above normal temperatures. Max temps Friday forecast to be upwards of 10+ degrees above normal, cooling to around 5+ degrees above normal by Sunday. Model differences increase early next week with GFS driving closed mid-latitude upper low into Central CA Monday while EC keeps it offshore. Forecast remains dry attm with highs Monday within a few degrees of seasonal normal.