Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
808 FXUS66 KSTO 180930 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 230 AM PDT Thu Jul 18 2024 .SYNOPSIS... Temperatures warm through the weekend with areas of Major and Extreme HeatRisk possible early next week. Thunderstorm chances return today to the Sierra south of Lake Tahoe and may spread a little further north over the weekend into early next week. && .Discussion... Skies are clear except for another batch of mid and high level clouds working their way northward from central California as monsoon moisture begins to return around the periphery of the upper high centered over the Desert Southwest. High pressure has begun to strengthen slightly over the region resulting in weakening onshore flow and a suppressed marine layer (depth down to around 1k ft or less). The result has been a return to milder temperatures with much of the Central Valley seeing current readings running around 5-10 degrees warmer compared to 24 hours ago. The ridge will "adjust" westward a bit over the next several days resulting in a gradual warmup with triple digit high temperatures returning to the Central Valley. Temperatures won`t be as extreme as the last heat episode with HeatRisk forecast to remain mainly in the Moderate category. Another short-wave trough is forecast to brush by NorCal over the weekend which will likely reinvigorate the Delta Breeze bringing localized cooling into the southern half of the Sacramento Valley while areas further inland remain hot. The return of elevated moisture/instability will lead to a chance for late-day thunderstorms over the Sierra, mainly to the south of Lake Tahoe, the next few days. Moisture/instability may spread further north over the weekend ahead of the approaching short- wave, but it appears stronger forcing/lift ahead of this feature will be focused to the north of the region over the PacNW. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Desert SW upper high extends over interior NorCal next week resulting in above normal temperatures. NBM showing high temperatures upwards of 10 degrees above normal with triple digit heat in the Central Valley. Widespread moderate heat risk expected with local areas of major to extreme heat risk. Highs from 100 to 108 expected, hottest in the N Sac Valley. Monsoonal moisture advecting around periphery of upper high could provide potential for thunderstorms, mainly during the afternoons, over higher elevations of the Sierra Nevada each day. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Sfc wind mainly below 12 kts except vcnty of Delta SWly sfc wind up to 20 kts possible at times. && .STO WATCHES/WARNINGS/ADVISORIES...None. && $$