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.