October 13, 2020 – High pressure 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, which may lead to critical fire weather conditions.
Discussion
We are going to see quiet weather for today as upper level ridging continues to build into NorCal. This will bring a continue warming trend with highs being a few degrees warmer than yesterday. The forecast does become more active on Wednesday as we see a trough dig out of Canada and deepen as it heads into the northern Rockies.
The Pacific ridge will also strength at this time creating an increased surface gradient over NorCal peaking late morning into the afternoon with a SAC to MFR gradient around 10-14 mb. The increased north winds begin Wednesday morning after 15z/8 am and peak during the afternoon with gusts 25-35 mph locally up to 40 mph across northern portions of the Sacramento Valley.
Valley winds will diminish some during the evening but will begin to increase in the southern Cascades, northern Sierra, and adjacent foothills Wednesday night. Winds of 15 to 25 mph with gusts to 35 mph are likely in these locations with higher gusts likely for the geographically-favored locations.
Winds on Thursday do not look as strong but we will continue to see an increased surface gradient over the region resulting in gusts up to 25-30 mph.
Gusty winds are expected once again Thursday night into Friday across the southern Cascades, northern Sierra, and adjacent foothills. Winds will likely be similar to Wednesday night for these locations. Low daytime humidity and moderate to poor overnight recoveries in the Foothills will accompany these winds leading to critical fire weather conditions.
A Red Flag Warning is in effect for much of the area Wednesday morning through Friday morning. Less wind is expected over the region by Friday mid morning as long wave troughing pushes into the Great Lakes region and the Northeast.
High temperatures will continue to be warm running 10-15 above normal through the end of the short term forecast.
Extended Discussion (Saturday through Tuesday)
High pressure from EPAC extends inland over interior NorCal Saturday, then gradually weakens into early next week. As a result dry weather continues with a cooling trend. Forecast high temperatures trend down from around 10 degrees above normal Saturday to near or a few degrees above normal Monday and Tuesday.