Another day of warm and dry weather today, with locally elevated fire weather conditions over the northern Sacramento Valley and northeast foothills. Slight chance (10-20%) for thunderstorms Wednesday afternoon/evening and again Friday, generally along and east of the crest. Temperatures cool to near to below normal Tuesday through Thursday before a warming trend takes hold Friday bringing widespread Moderate Heat Risk for the weekend, with triple digit Valley highs.
Discussion
Little change today with upper level ridging over the area and a trough over the Pacific Northwest and Gulf of Alaska. Highs will be in the mid to upper 90s in the Valley, 80s to 90s in the foothills.
There will be one more day of elevated fire weather concerns today for the northern Sacramento Valley and adjacent foothills in the afternoon, with minimum RH values still look to bottom out in the teens to low 20s this afternoon coinciding with some breezy southerly winds.
Most areas elsewhere should have good to moderate humidity recovery this morning, which will limit fire weather concerns.
Ensemble guidance continues to show the trough will deepen along the coast Tuesday, shifting the ridge eastward and bringing increased onshore flow and cooler temperatures into Thursday. This stronger onshore flow will bring in marine moisture with an upward trend in humidity levels through Thursday, which should further reduce fire weather concerns across much of the area.
There will be breezy winds at times, especially for areas influenced by the Delta Breeze, with gusts in the Valley up to 20-25 mph.
High temperatures cool to 3 to 8 degrees below normal for Wednesday and Thursday, with highs in the Valley generally in the mid 80s to lower 90s. Monsoonal moisture moving northward over the Sierra will bring a slight (10-20%) chances for isolated thunderstorms on Wednesday afternoon, south of Highway 50, with better potential east of the Sierra crest.
Tuesday has trended drier on the west slopes, with convection mainly east of the crest.
Extended Discussion (Friday through Monday)
Friday a shortwave moves through over far northern California, with enough instability and moisture to bring a slight (15-20%) chance of afternoon and evening showers and isolated thunderstorms to Lassen National Park and portions of eastern Shasta County.
Ensembles and clusters show an upper level high will build and expand westward over Friday through the weekend, bringing a warming trend with daytime high temperatures 3 to 7 degrees above normal by Saturday.
The hottest day will be Sunday when high temperatures will be 5-10 degrees above normal for this time of year. According to the NBM, the Sacramento Valley, Delta, and foothills have a 60-95% chance of triple digit high temperatures with higher likelihoods centered over the northern Sacramento Valley on Sunday.
Widespread Moderate Heat Risk will return to interior California starting Saturday and remain through Sunday.
Take extra precautions when venturing outside this weekend as the heat will affect most individuals with heat-sensitivity. Stay hydrated, remain in adequately cooled facilities, and limit time outside.