874 FXUS66 KSTO 301935 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1235 PM PDT Fri Jun 30 2023 .SYNOPSIS... Very hot and dry conditions continue with peak heat expected this weekend. Gradual cooling trend next week with temperatures returning to near to below normal late in the week. && .DISCUSSION... Latest GOES-West visible satellite imagery illustrates abundant sunshine being observed across interior northern California on this Friday afternoon. Current temperatures are already trending 5 to 15 degrees warmer than this time yesterday, valid at 1230 PM PDT. Redding Airport already reached 100 degrees before noon today. This warming trend bringing dangerous heat to the area will be the main weather element of concern over this holiday weekend. An upper level ridge will be the dominant feature this weekend, and as high pressure builds across the region, temperatures will be on the rise. Temperatures will be trending upwards of 10 to 15 degrees above normal for late June/early July climatology. Widespread triple digits are forecast through the weekend for the Valley and foothills. Overnight temperatures will also be trending above normal. This combination will lead to Major Heat Risk in the Valley and foothills, and Moderate Heat Risk in the mountains. This level of heat affects anyone without effective cooling and/or adequate hydration. The peak heat is forecast to be this weekend. Morning low and daytime high temperatures will be trending slightly cooler on Monday, but still hot, as the high pressure area shifts eastward and onshore flow increases. Confidence is high for these dangerous temperatures, and people should take precautionary measures to stay safe in the heat, especially those who plan on spending time outside this holiday weekend. The Heat Advisory for the Delta region, southern Sacramento Valley and Coastal range remains in effect through 11 PM PDT Sunday evening. The Excessive Heat Warning remains in effect for the rest of the Valley and foothills through 11 PM PDT Sunday evening as well. Stay hydrated, know where to find shade/cooling, and take frequent breaks during outdoor activities. Be sure to check up on vulnerable populations as well during this heat event. Additionally, area waterways continue to run cold and fast across the region from snowmelt, and the California Nevada River Forecast Center (CNRFC) is still reporting water temperatures in the 50s in portions of the American River, and 60s in portions of the Sacramento River. Even with hot temperatures in the forecast, cold water can still cause loss of muscle control quickly. Be smart around area waterways! For more information on Heat Risk: wrh.noaa.gov/wrh/heatrisk/ For more CNRFC water temperatures: cnrfc.noaa.gov //KH & .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Latest cluster analysis indicates a flattening of the ridging aloft by midweek next week, with some hints at weak troughing building in across interior northern California as well. This will result in a gradual cooling trend across the middle and latter portions of the week ahead. In general, lower triple digits are still anticipated within the northern Valley on Tuesday, with mid to upper 90s across the southern Sacramento Valley, and 80s to low 90s expected elsewhere. Temperatures generally cool to near normal values for Wednesday and Thursday, with near to slightly below normal temperatures favored moving toward next weekend. Increased onshore flow will accompany these cooling temperatures, bringing locally breezy conditions, especially through the Delta region. Otherwise, despite the presence of troughing aloft, given dry antecedent conditions, precipitation chances remain low (less than 5% for all areas at this time). && .AVIATION... General VFR conditions over interior NorCal next 24 hrs. Surface wind mainly below 12 kts. except in the vicinity of the Delta, where winds to 20 kts are possible at times. MVFR/IFR ceilings are possible over the western Delta 12-17z Saturday. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 11 PM PDT Sunday for Central Sacramento Valley-Motherlode-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley. Heat Advisory until 11 PM PDT Sunday for Carquinez Strait and Delta-Mountains Southwestern Shasta County to Western Colusa County-Southern Sacramento Valley. && $$