Dry weather with temperatures warming into the weekend. Chances for mountain thunderstorms in the northern Sierra return late weekend into early next week south of I-80.


Some high clouds from the Desert SW are spreading northward over the CWA early this morning, with cloud cover lingering over the Sierra into the afternoon. Otherwise, mostly clear skies and dry weather continue with highs running roughly 3 to 8 degrees above normal. High pressure continues to expand over interior NorCal through the weekend with the warmest day still expected to be Saturday.

The warmest locations are expected in the northern Sacramento Valley with highs anywhere from 100 to 110 degrees, with “cooler” temperatures further south due to the Delta influence. Widespread moderate heat risk is expected for much of the Valley/foothills this afternoon which may impact those sensitive to heat or without adequate cooling.

High pressure moves slightly further west on Sunday with decent mid-level moisture extending back over much of Central and Northern California bringing a slight chance for a storm over the Sierra Sunday afternoon and evening (more likely a shower as the better instability lies further south than our CWA).

Interior NorCal will be stuck in between weak troughing across the PacNW and a low pressure that forms off the southern California coast on Monday. This will bring some increased onshore winds and the return of near average temperatures Monday. Slightly more favorable moisture/instability are seen on Monday as well with another chance for mountain storms over the Sierra, mainly south of I-80.

Extended Discussion (Tuesday through Friday)

Broad high pressure is expected to remain over much of the Central to Western US next week. Ensembles continue to show the western edge of the high pressure ridge remaining over California through at least the end of next week, which will continue bringing mid- level monsoon moisture into the area.

Afternoon and evening isolated thunderstorms are forecast each day across the Sierra, mainly south of I-80, though some model guidance is indicating thunderstorms could form as far north as the Shasta County mountains on Tuesday. With PWAT values forecast around 0.75 to 1 inch, high elevation thunderstorms would produce precipitation.

However, as always during this time of year, any lightning strikes outside of rain core have the potential for fire starts, so it is important to be weather aware.