Dry weather with temperatures gradually warming heading into the weekend. Chances for mountain thunderstorms in the northern Sierra return early next week.


IR imagery indicates primarily clear skies over interior Northern California this evening, with some scattered clouds over the northern Sierra crest. SFO-SAC gradient is roughly +2.6 with wind gusts up to 30 mph observed near the Delta early this morning bringing the coolest conditions to areas around this location. Elsewhere, lows will bottom out anywhere from the mid-50s to up to 70 degrees, warmest in the thermal belt. Mountain lows are generally in the 40s and 50s.

Another warm day is expected this afternoon with highs generally expected to be a degree or two warmer than those seen yesterday. The biggest warm up is expected Friday into the weekend as high pressure expands across the southwest US.

Highs across NorCal creep back up to roughly 5-7 degrees above normal, with the warmest day expected on Saturday. Moderate heat risk is expected in the warmest locations, generally the northern Sacramento valley and thermal belts. Mid-level moisture increases Saturday into Sunday across the area, although it looks like any storm potential on Sunday afternoon/evening will be south or east of our area. The better potential for mountain storms is expected early next week (see extended discussion).

Extended Discussion (Monday through Thursday)

Ensemble guidance is in good agreement of the general synoptic pattern for the extended period. High pressure looks to remain centered over the Four Corners region with weak troughing off of the PacNW coast. The high pressure is forecast to expand west into northern California, bringing a surge of monsoon moisture.

Mountain thunderstorms will be possible each afternoon and evening, mainly in the Sierra south of I-80. Onshore flow with a decent Delta Breeze is forecast to continue. Temperature forecast remains within a few degrees of daily normals, generally in the mid 90s to 103 degrees in the Valley and foothills and 70s to low 80s in the mountains.