Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
772 FXUS66 KSTO 042033 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 133 PM PDT Fri Oct 4 2024 .Synopsis... Well above normal temperatures persist through the weekend, with Moderate to Major HeatRisk in the Valley, Delta and foothills. Gradual cooling trend next week, with potentially some showers late in the week. && .Discussion... Unseasonably hot temperatures continue today and over the next several days across the area, with widespread Moderate to Major HeatRisk in the Valley and foothills, especially from Interstate 80 southward. The 4-Corners ridge which extends into the region will be flattened a bit today as a trough passes through, mainly over the Pacific Northwest. As a result, highs today will be a little less hot than yesterday. West to southwest winds are increasing with this trough, mainly over mountain ridges. This is leading to elevated fire weather conditions this afternoon and evening, especially for the higher Sierra and into the Burney Basin. While the weather remain dry today, there is enough mid level moisture to spread some clouds through the area. The ridge will quickly rebound, with highs highs 15-20 degrees above normal over the weekend. Forecast highs are expected to be in the 90s to around 104 degrees in the Valley and Delta. Sunday is expected to be the hottest day in the forecast period, with some daily record highs also possible on Saturday, including for Sacramento and Stockton. HeatRisk has trended higher over the weekend, and so the Heat Advisory has been extended through Sunday evening at 11 PM PDT for the southern Sacramento Valley, Delta area, northern San Joaquin Valley and Motherlode. Some cooling is expected Monday as a weak trough moves in, with onshore flow developing. This will be the begining of a cooling trend for the week. The latest National Blend of Models temperatures for Monday have trended a little warmer, though, so this cooling trend will be a gradual one to start. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Weak upper troughing moves through Tuesday providing minor synoptic cooling, but forecast high temperatures continue to be above normal through the middle of next week. Ensemble guidance and cluster analysis is in general agreement for upper level troughing across the Eastern Pacific Ocean to then develop and approach from the west mid to late next week. This will assist in cooling temperatures, and bring increased onshore flow to the forecast area. HeatRisk decreases to Minor for the Valley and foothills over the extended forecast period as a result of the gradually cooling temperatures as they return closer to the climatological normal for early to mid October. Additionally, precipitation chances return to the forecast for the end of next week. The National Blend of Models (NBM) currently advertises about 15-35% probability for a tenth of an inch of precipitation or greater for Friday, with best chances north of Interstate 80. There is still quite a bit of uncertainty for details and timing of any precipitation but either way, relief from the heat looks promising as we progress into next week. && .AVIATION... VFR conditions across interior NorCal over the next 24 hrs. Surface wind speeds generally at or below 12 kts except local surface wind gusts of 20-30 kts over higher mountain terrain through 06Z Saturday. && .STO WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 11 PM PDT Sunday for Carquinez Strait and Delta-Motherlode-Northern San Joaquin Valley-Southern Sacramento Valley. && $$