Heat to peak by Tuesday

August 24, 2019 – Above normal temperatures through midweek, peaking Tuesday, then returning to near to slightly above normal by Friday. Dry weather continues.

Discussion

EPAC upper ridge extends inland over NorCal with onshore gradient producing strong flow through the Carquinez Strait early this morning.

Marine layer is about 2400 feet deep at Fort Ord and combined with strong Delta breeze is resulting in low level CAA into portions of the Sacramento Valley. This evident by 24 hour change graphs showing most locations in the Central Valley are cooler with higher humidity.

Delta breeze weakens some during the morning hours, but remains moderate enough to influence high temperatures in portions of the Sacramento and Northern San Joaquin Valleys today. Expect to continue to see triple digit heat in the Northern Sacramento Valley today with slightly cooler readings elsewhere in the Central Valley, i.e., mid to upper 90s. Strong subsidence and dry AMS will hinder any mountain deep moist convection today.

Heights and thicknesses slowly trend up into early next week as Desert SW upper high builds towards the northwest. 850 mb temps top out Tuesday afternoon, climbing into the mid to upper 20s Deg C. Bought dry adiabatically to the surface results in max temperatures Tuesday around the century mark for much of the Central Valley.

Hottest readings expected in the Northern Sac Valley with around 107 forecast at Redding. Overnight lows look to cool into the 60s for most Valley locations, so attm not expecting the need for widespread heat products.

Upper ridge axis shifts into the Intermountain West Wednesday as several upper lows off the California coast progress. This will begin a slow cooling trend with increasing onshore flow that will drop temperatures to near to slightly above normal by the end of the week.

Extended Discussion (Wednesday through Saturday)

High pressure over the western U.S. for fair skies and above normal temperatures during the start of the extended period Wednesday. Daytime highs are forecast to come in a few degrees above normal. A slow cooling trend is forecast through the end of the week as a long wave trough develops over the eastern Pacific and shortwave troughs pivot into the Pacific Northwest. Forecast remains dry through the end of the extended with daytime highs coming in just slightly above normal.