Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
730 FXUS66 KSTO 092033 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 133 PM PDT Sun Aug 9 2026 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .KEY MESSAGES... - Widespread Moderate to areas of Major HeatRisk continue through today. - Gradual cooling trend Monday onward with more seasonable temperatures and periods of breezy onshore winds through the week. - Elevated Fire Weather Conditions in the northern Sacramento Valley, Burney Basin, Sierra, and adjacent Foothills through Monday due to hot temperatures, low humidities and increased breezes. - Isolated thunderstorm (15%) chances along the Sierra Crest south of Interstate 50 this afternoon and evening. - Monsoonal moisture will bring increasing chances of mountain thunderstorms Tuesday through Saturday, peaking on Thursday. && .DISCUSSION...The heat wave is expected to continue through today, with widespread triple-digit high temperatures across the Valley and foothills. There is a widespread Moderate HeatRisk and areas of Major HeatRisk across interior NorCal. The heat will impact anyone without effective cooling and/or adequate hydration. A Heat Advisory remains in effect through 10 PM this evening for the Valley and foothills, as well as mountain locations north of Highway 50. Elevated fire weather conditions continue through Monday due to hot, dry, and breezy winds conditions in the northern Sacramento Valley, Sierra foothills, and Burney Basin. Low relative humidities in the single digits to teen`s percent are forecast today for the mentioned areas. Additional elevated fire weather concerns today for the Sierra Crest south of Highway 50 due to 10-15% isolated thunderstorm chances this afternoon and evening, with the majority of the activity remaining east of the crest. The upper-level ridge over the Four Corner will begin to breaks down on Monday, while a mid- to upper- level shortwave trough develops off the West Coast. Onshore flow is expected to increase in response, providing a broader overnight relief and increasing humidity values. Resulting in slightly cooler temperatures on Monday, with more seasonable temperatures on Tuesday. Ensembles continue to suggest the upper-level trough settles over the region by middle week, bringing more widespread cooling, with near to below normal temperatures and Minor HeatRisk area wide late in the week. Monsoonal moistures will bring increasing chances of mountain thunderstorms Tuesday through Saturday, with the highest chances (25-35%) Thursday. There is a 30-60% chance of wetting rain over the Sierra Crest south of Highway 80 on Thursday, with 15-30% chances over far northern Sierra and into the southern Cascades. Additional, there is low chances (10%) for thunderstorms over the Sierra foothill as well on Thursday. Elevated fire weather is expected Tuesday through the weekend from thunderstorm fire starts. Stay tuned for updates! && .AVIATION... VFR conditions are expected to prevail over the next 24 hours. Winds generally remain 12 kts or less at TAF sites. West to southwest gusts up to 20 kts in the Delta from 00Z through 12Z Monday. && .STO WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 10 PM PDT this evening for Burney Basin- Butte County Below 1000 ft-C. San Joaquin County including Stockton-C. Stanislaus County including Modesto-C. Yolo/NE Solano including Woodland-Central Colusa County Incl. I-5- Central Glenn Co & Interstate 5-Central Motherlode 1000-3000 ft- E. Diablo Range Above 1000 ft-E. Shasta /S. Cascades Above 3000 ft-Eastern Colusa County-Eastern Glenn County-Glenn/Colusa Coast Range Above 3000 ft-Lassen Volcanic NP-N. Motherlode 1000-3000 ft-N. Sac Valley in Tehama County-NE San Joaquin Valley Below 1000 ft-Sac Metro/W. El Dorado/Amador County-San Joaquin County Delta-Shasta County Foothills 1000-3000 ft-Shasta Lake Area & 1- 5 1000-3000 ft-Shasta Metro-Sierra (Cal-Tuo) 3000-5000 ft-Sierra (Sierra-Placer) Above 5000 ft-Sierra (Tehama-Plumas) 1000-3000 ft-Sierra (Tehama-Plumas) Above 3000 ft-Sierra (Yuba-Placer) 3000-5000 ft-Sierra 3000-5000 ft-Southern Motherlode 1000-3000 ft-Sutter/Yuba counties below 1000 ft-Tehama Co Coast Range Above 3000 ft-Tracy Triangle Below 1000 ft-W Tehama Co Foothills 1000-3000 ft-W. Glenn/Colusa Foothills 1000-3000 ft-W. Shasta County 1000-3000 ft-W. Shasta County Above 3000 ft-W. Stanislaus County Above 1000 ft & I-5-W. Yolo County including Capay/I-505- Yolo / Solano County Hills. && $$