Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
279 FXUS66 KSTO 040939 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 239 AM PDT Thu Jul 4 2024 .SYNOPSIS... Widespread Major to Extreme HeatRisk into the middle of next week. Elevated fire weather concerns in the Valley and adjacent foothills due to very hot and dry conditions. && Key Points - Long-duration, dangerous heat event into mid next week, impacting holiday outdoor events. - 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. .Discussion... Anomalously strong high pressure will dominate the pattern through the forecast period, bringing an extended period of dangerous heat. The EFI also highlights the extreme nature of this heat event. 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 30 to 75% chance in the southern Sacramento and northern San Joaquin Valleys Friday-Saturday. Daytime highs will range from 105-118 degrees across the Valley, Delta, and foothills, with 80s to around 110 in the mountains. The hottest temperatures are still expected on Friday-Saturday. Overnight temperatures will provide little to no relief from the heat with lows ranging from the upper 60s to mid 80s; warmest in the thermal belt regions of the foothills. Widespread Major to Extreme HeatRisk is expected across the Valley and foothills, with Major HeatRisk over the mountains. This level of rare, long-duration extreme heat with little to no overnight relief affects anyone without effective cooling and/or adequate hydration. 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 until 11 PM Tuesday. Check on sensitive groups, stay hydrated, strongly consider canceling outdoor activities, and stay in a cool place, including overnight. DO NOT leave children or pets in unattended vehicles. The extended period of very hot and dry conditions will bring elevated fire weather concerns to the Valley and foothills. Know your wildfire risk and have an emergency plan in advance. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Ensembles and clusters show a gradual eastward progression of the upper high late weekend into next week, resulting in a minor downward trend in high temperatures through midweek. High temperatures in the 105-113 F range are still anticipated through early next week in the Valley and foothills, with a slight cool down closer to highs in the 100-110F range into mid next week. Some overnight relief from the heat will be possible early next week near the Delta Breeze influenced areas. Low temperatures into the low to mid 60s will be possible in these areas through mid next week, with upper 60s to mid 70s still likely through the remaining Valley and adjacent foothills locations. In terms of HeatRisk, widespread Major to Extreme HeatRisk is expected through early next week, with Moderate HeatRisk near Delta influenced areas. By mid-week, widespread Moderate HeatRisk is expected across the region, with some areas of Major/Extreme HeatRisk (mainly in the foothills). && .AVIATION... VFR conditions expected across interior NorCal next 24 hours. Increasing south to west gusts to 20 kts in Delta and immediate vicinity through approximately 00z Friday. && .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. Heat Advisory until 11 PM PDT Tuesday for Burney Basin / Eastern Shasta County-West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$