Triple digit heat continues across the Central Valley through the weekend with gradual cooling next week. Mainly dry weather expected except for a slight chance for Sierra showers and thunderstorms Saturday. Heat Advisory from 11 AM Saturday to 9 PM PDT Sunday.
Discussion
Upper level ridge is going to be building over the west today into the weekend. Highs today will be very similar to yesterday but we will see slight warming over the weekend mainly over the northern part of the area as the ridge amplifies. 850 mb temps warm to 25-26 C over the northern Sacramento Valley which should result in daytime highs 103 to 107 over the weekend.
Overnight lows will also be mild over the northern Valley with lows falling into the mid 60s to mid 70s, warmest in the foothills. This slight bump in temperatures is enough to push heat risk into Advisory territory.
Went ahead and issued a Heat Advisory for the central and northern Sacramento Valley and adjacent foothills for saturday and Sunday. Onshore flow and evening and overnight Delta Breezes will keep the Delta and Sacramento area slightly cooler, keeping things below advisory thresholds.
A short wave under the ridge will push over NorCal on Saturday and we will see instability build over the Sierra. This will bring the chance for a few showers and thunderstorms mainly towards the crest from about I-80 south during the afternoon. With weak dynamics we are not expecting organized storms but a few short lived storms with small hail will be possible. PWATs will be 0.50-0.75″ and a brief period of heavy rain will also be possible with any of the stronger storms. Thunderstorm chances diminish quickly in the early evening with dry weather expected on Sunday.
The ridge will start to push to the east early next week as a trough begins to push into the PacNW. This will bring gradual cooling to the area but it will remain warm for the start of the week.
Extended Discussion (Tuesday through Friday)
Quiet weather is expected for the extended period with a continued cooling trend as troughing builds over the west coast. This will bring more seasonal highs by the middle part of the week with the potential of below normal highs by the end of the week. Onshore flow with evening and overnight Delta Breezes will continue.