Very hot temperatures will continue for far northern California today. Breezy winds are expected through the Delta at times. Slight chance for isolated afternoon and evening thunderstorms across the High Sierra south of Highway 50 this weekend and into early next week.
Discussion
Another very hot day is in store today as an upper-level ridge remains centered over far northern California. Yesterday, Redding area established a new daily record high of 114 deg F, besting the previous record of 113 deg F set in 2003 and 1923. Highs this afternoon will be near or a few degrees cooler compared to yesterday. Latest run of the National Blend of Models gives Redding a 72% chance of >= 110 deg F and a 55% chance of >= 113 deg F today. Excessive Heat Warning remains in effect for the northern and most of the central Sacramento Valley, and the adjacent foothills and mountains through 9 PM this evening.
Upper-level high center begins to drift east toward the Great Basin after tomorrow and through the weekend as a trough digs offshore along the 130W meridian. This will promote much-welcomed day-to-day cooling for far northern California communities for both Saturday and more so on Sunday.
Increasing surge of moisture from the south will arrive to central and northern California over the weekend, introducing better chances of afternoon/evening showers/thunderstorms in the mountains. Best chance on Saturday will generally be confined along/south of US-50 with chances extending north all along the crest for Sunday. PWAT anomalies will remain elevated — upward of 150-200% of normal — so think the dry lightning threat will be low as any convection would have plenty of moisture to work with. Mountain shower/thunderstorm chances will continue on Monday as temperatures continue to moderate.
Extended Discussion (Tuesday through Friday)
Cluster analysis in the extended introduces some forecast uncertainty with the progression of the trough off the West Coast. Should still see a chance of mountain showers/thunderstorms on Tuesday, but am less confident on the coverage. Regardless of the trough`s exact evolution, should see continued onshore flow with periods breezy south/west winds. Additionally, Valley highs will likely struggle to get out of the 90s for the first half of the work week. Probability of hitting 100 deg F for Redding on Tuesday and Wednesday next week is only 37% and 21%, respectively.