Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
446 FXUS66 KSTO 030958 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 258 AM PDT Wed Jul 3 2024 .SYNOPSIS... Widespread Major to Extreme HeatRisk into the middle of next week. Critical fire weather conditions in the Sacramento Valley and adjacent foothills through this evening. && Key Points - Long-duration, major heat event into mid next week, impacting holiday outdoor events. - Red Flag Warning is in effect for much of the Sacramento Valley and adjacent elevations below 3000 feet through this evening. - Excessive Heat Warning remains in effect for the Valley, Delta and foothills through 11 PM Tuesday. - Heat Advisory remains in effect for the Sierra, southern Cascades, and Burney Basin from 11 AM today until 11 PM Tuesday. - High likelihood of this heat continuing through mid next week .Discussion... Northerly wind gusts of 15-30 mph are being observed across portions of the western half of the Sacramento Valley and adjacent foothills early this morning. Strongest winds are expected this morning. The combination of gusty winds and very low humidity will lead to critical fire weather conditions through this evening. A Red Flag Warning remains in effect for much of the Sacramento Valley and surrounding foothills below 3000 ft until 8 PM today. Ensembles and clusters depict a strong, anomalous high pressure remaining overhead through the forecast period. This will result in a prolonged, dangerous heat event across the region. Daytime temperatures will range from 105 to 118 degrees in the Valley and adjacent foothills; peaking on Friday-Saturday. NBM probabilities indicate a 75-100% chance of high temperatures of 110 deg F or higher through the northern and central Sacramento Valley, and a 50 to 80% chance in the southern Sacramento and northern San Joaquin Valleys. Little relief is expected overnight with lows forecast in the upper 60s to mid 80s; warmest in the foothills. As a result, widespread Major to Extreme HeatRisk is expected across interior NorCal. This level of HeatRisk is VERY DANGEROUS to anyone without proper hydration or adequate cooling. Strongly reconsider any outdoor activities during this prolonged heat event. DO NOT leave children or pets in unattended vehicles. Car interiors will quickly reach lethal temperatures in a matter of minutes. An Excessive Heat Warning remains in effect for the Valley, Delta, and foothills until 11 PM Tuesday. Additionally, a Heat Advisory remains in effect for the Sierra, southern Cascades, and Burney Basin from 11 AM today until 11 PM Tuesday. && .EXTENDED DISCUSSION (Sunday THROUGH Wednesday)... 597 DM upper high over NorCal Sunday slowly shifts into early next week. Heights/thicknesses gradually decrease through the extended period resulting in a slow downward trend in high temperatures through the middle of next week. Weak meso upper low depicted by models off the Central CA coast early next week. This could allow for some deepening of the marine layer and begin to provide some cooling for Delta breeze influenced areas. Remainder of interior NorCal continues well above normal temperatures through the extended period. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. In Sac Vly, areas of Nly sfc wind 15 to 20 kts til 00z Thu and SWly up to 20 kts vcnty of Delta aft 00z Thu. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 11 PM PDT Tuesday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County- Southern Sacramento Valley. Red Flag Warning until 8 PM PDT this evening for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-Eastern Portion of Shasta/Trinity NF-Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft- Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units-Southeast Edge Shasta- Trinity NF and Western Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo-Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft. Heat Advisory from 11 AM this morning to 11 PM PDT Tuesday for Burney Basin / Eastern Shasta County-West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$