July 13, 2020 – Dry weather with seasonably hot temperatures continuing, though Delta influenced areas will see a bit of a break from triple digit heat this week. Thunderstorms will be possible near the crest Wednesday and Thursday.
Discussion
Trough pushing through the Pacific Northwest has initiated delta breeze tonight with southwest gusts to 35 mph through the delta at KSUU. This will allow overnight temperatures to cool about 5 degrees more than last night.
Onshore flow pattern will continue for the Srn Sacramento and Nrn San Joaquin Valleys through the end of the week with temperatures running near to slightly above normal.
However, temperatures will get progressively warmer, moving north through the valley with the Redding area staying in the 104 to 109 range for highs through the week, which is 3 to 8 degrees above normal. Wednesday will be the hottest day with a high of 109 currently being forecast. This would push heat levels to moderate/high over portions of Shasta county and a heat product may be needed for Wednesday.
Trough will try to split a bit Wednesday with weak cut-off low developing just off the SoCal coast. This may be enough to develop a southerly mid-level flow over the Sierra, advecting just enough moisture moisture for a few isolated thunderstorms near the high Sierra crest. The Best chances look to be Wed/Thur south of highway 50.
Extended Discussion (Friday through Monday)
NorCal will remain in between monsoon high over the Four Corners region and westerly flow regime over the Pacific Northwest through the extended.
Just enough trough weakness should continue to extend south along the West Coast to keep weak delta flow moving into the Valley. This will likely moderate temperatures enough to prevent excessive heat with current forecasts indicting highs from 3 to 5 degrees above normal through the weekend.