May 7, 2020 – Breezy northerly winds persist today. Dry weather continues with well above average highs into the weekend. Cooler weather along with precipitation chances returns early next week.
Discussion
Dry north to northeast flow continues across the region early this morning. The MFR-SAC gradient is holding around 11 mbs while the RNO-SAC gradient has increased to over 6 mbs. Current surface observations indicate northerly gusts in the teens to 20s mph across the northern and western portions of the Sacramento Valley. RH’s in this area are also very low, in the teens to mid 20s percent. Local northeast wind gusts of 20 to 40 mph are also present across the foothills and west slopes of the northern Sierra Nevada.
Local elevated fire weather conditions will persist today across breezier portions of the Sacramento Valley and adjacent foothill areas where seasonal grasses and other fine fuels have already cured, and where humidities will be in the upper single digits and low teens. Wind gusts will begin to decrease this afternoon, and the northerly breezes will diminish by this evening as surface gradients relax.
Warmth will increase across the region today as the ridge along the West Coast amplifies ahead of the evolving trough centered over the Gulf of Alaska. Highs today are expected to be around 5-10 degrees warmer compared to Wednesday and will top out in the mid 90s across portions of the Central Valley.
The peak of this early season heat episode is expected on Friday, though many areas will remain hot into Saturday. Lighter north winds will continue to result in local adiabatic warming across portions of the Sacramento Valley where some areas may see their first triple digit heat of the season, and potentially set daily record highs.
Ensembles in good agreement indicating the upper ridge axis will begin to shift east into the Great Basin by Saturday afternoon. This should allow a return of the Delta Breeze resulting in slight cooling across the southern half of the Sacramento Valley while the remainder of the region stays hot for another day.
More substantial cooling forecast to begin on Sunday as stronger southwest flow spreads across the area ahead of the approaching trough over the eastern Pacific.
Extended Discussion (Monday through Thursday)
Minimal changes to the extended forecast as models and ensembles continue to show a pattern change. A deep closed upper level low from the Gulf of Alaska is expected to dig into the region on Monday. This will bring a significant change in the temperature regime in addition to accumulating precip to portions of the region.
Guidance continues to trend towards wetter weather arriving similar in timing by Monday evening (06z Tuesday) spreading precip over most of our CWA by then. A secondary front is forecast to reinforce cooler air and showery weather over most of our area on Tuesday and Tuesday. Precip looks to linger over the northern mountains on Wednesday. With the placement of the low and the showery activity, we’ll have to keep a close eye on convective ingredients. Thunderstorms could be possible in the northern zones.