Hot today into Wednesday, then cooling Thursday into the weekend. Chance of afternoon showers or thunderstorms over the Sierra Nevada through Wednesday. Elevated Fire Weather conditions Wednesday and Thursday due to gusty southerly winds and low RH values.
Discussion
594 DM upper high centered over the Great Basin will continue to strengthen today resulting in hot weather over interior NorCal. High temperatures expected to be similar to Monday with triple digit heat throughout the Central Valley and in portions of the Delta and foothills. Major heat risk projected today across much of the Central Valley with highs from 105 to 112, hottest in the N Sac Valley. Deepening thermal low over the Central Valley this afternoon will result in some increased southerly flow. Chance of afternoon showers or thunderstorms over higher elevations of the Sierra Nevada from about I-80 southward.
RH progs continue to show a gradual increase in midlevel moisture over the area today into Wednesday. 850 mb temps lower a degree or two tomorrow with max T’s a few degrees cooler. Delta breeze strengthens tonight into Wednesday. Thermal low further deepens over the Sac Valley tomorrow with some increased afternoon southerly surface wind. This could result in a brief period of elevated fire weather conditions.
More significant cooling forecast Thursday into Friday as heights/thicknesses lower in response to deep short wave trough moving through the PacNW and cutoff low progged through the CWA on Friday. Synoptic cooling with deepening marine layer and increased onshore flow expected. Enhanced midlevel SWly flow should keep any Sierra Nevada deep moist convection crest eastward. Locally gusty wind continues to be possible during the afternoons as humidity trends up into Friday.
Extended Discussion (Saturday through Tuesday)
Broad upper troughing progged to remain off the West Coast through the weekend into early next week. NBM advertising near to slightly below normal high temperatures. 90s expected in the Central Valley with 80s in Delta breeze influenced areas, and mainly 70s and 80s for the mountains and foothills. Dry weather forecast through the extended period.