Chance of thunderstorms in the high country on Wednesday

July 14, 2020 – Dry weather with hot temperatures over the Northern and Central Sacramento valley, while Delta influenced areas see a break from triple digit heat this week. Isolated thunderstorms will be possible near the Sierra crest Wednesday and Thursday.

Discussion

Weak Trough over the Pacific Northwest will extend south just far enough to lower heights a bit along the west coast. This will keep delta breeze going over the next few days with southwest gusts to 35 mph through the delta at KSUU at times. As a result, onshore flow pattern will continue over 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 110 range for highs through the week, which is 3 to 9 degrees above normal.

Wednesday will be the hottest day, helped by downslope northerly flow during much of the day, with a high of 110 currently forecasted. This will push heat levels to moderate/high over portions of Shasta county for a short duration. Residents across Shasta county should limit outdoor exposure Wednesday afternoon.

Trough will split a bit Wednesday with weak cut-off low developing just off the SoCal coast. This will develop just enough southerly mid-level flow over the Sierra to advect moisture north for a few isolated thunderstorms near the high Sierra crest. The Best chances look to be Wed/Thur, especially south of Interstate 80.

Extended Discussion (Saturday through Tuesday)

NorCal will remain between monsoon high over the Four Corners region and westerly flow regime over the Pacific Northwest through the extended. Southwest flow in this pattern is expected to push moisture east into Nevada through the weekend, ending mountain thunderstorm chances.

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 6 degrees above normal through the weekend.