Dry weather with warming temperatures through mid-week. Triple digit heat returns to the Central Valley Tuesday through the weekend, peaking on Wednesday. Monsoon moisture may produce isolated showers and thunderstorms over the high Sierra south of Highway 50 late this week.
Clear skies cover interior NorCal early this morning, though some mid and high clouds are beginning to drop southeast into northwest California as another short-wave approaches. Offshore surface pressure gradient has tightened over most of the area resulting in northerly gusts around 10-15 mph in the Sacramento Valley, and local northeast gusts of 15-30 mph in the northern Sierra. A waning onshore gradient now has the southwest breeze down to around 10 mph at Travis AFB.
Current temperatures are running around 5-10 degrees milder across much of the area compared to early Sunday and range from the upper 50s to around 70 in the Central Valley. Short-wave drops south today forming a closed low along the central California coast through mid-week. Ridging to the north of this feature will result in continued warming into Wednesday as subsidence and a suppressed marine layer dominate.
Highs today will edge upward another notch, reaching the 90s across the Central Valley. Triple digit heat returns to the valley Tuesday and Wednesday with moderate, to locally high, heat risk. Highs will likely peak for most of the area on Wednesday when areas north of Sacramento will see readings around 105, or slightly above.
Northerly breezes of 15-25 mph are expected in the Sacramento Valley through Tuesday, and combined with lowering RH will result in elevated fire weather conditions. Local easterly breezes of 25-35 mph will be possible tonight and Tuesday morning in the usual windy spots of the northern Sierra west slopes.
Ensembles still indicate the closed low will open and lift out to the northeast on Thursday, but may draw enough mid and upper level moisture northward for a few late-day thunderstorms across the higher elevations of the Sierra to the south of I-80. Temperatures may edge down slightly.
Extended Discussion (Friday through Monday)
Ensembles and clusters show flat ridging building over NorCal Friday and into the weekend with westerly flow developing. This will push monsoonal moisture eastward into Nevada and the Rockies. Could still see an isolated thunderstorm near the Sierra crest Friday with lingering moisture. Warm temperatures and moderate heat risk can be expected in this pattern with Valley high temperatures from 95 to 105 degrees through the weekend. Coolest near the Delta and Southern Sacramento Valley where some late afternoon Delta breezes may moderate temps.