187 FXUS66 KSTO 212039 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 139 PM PDT Sat Jun 21 2025 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .DISCUSSION... .SYNOPSIS... An active, but predominantly dry weather pattern will keep windy and cool weather through the weekend, introduce a return to near normal temperatures and onshore flow, alongside slight mountain thunderstorm chances into the early week ahead, followed by potential for above normal temperatures mid to late week. && .KEY MESSAGES... * Red Flag Warning in effect through 9 AM PDT Sunday for Delta, Valley, and foothills locations below 3000 feet. * Today - Sunday: -Elevated to critical fire weather conditions expected due to the combination of: --North to west winds gusting 30 to 40 mph through Sunday morning, then gradually decreasing into Sunday afternoon, and --Daytime relative humidity around 15-25% with only modest overnight recovery. -Seasonably cool temperatures expected, with Valley high temperatures in the 80s and 60s to 70s at higher elevations. -Please continue to practice fire safety such as, properly extinguishing any campfires, not driving over dry grass, checking your vehicle for chains or hanging objects that may cause sparks. * The Week Ahead: -Gradual warming trend through midweek with temperatures returning to seasonal normal values. Valley high temperatures in the 90s with 70s to 80s expected at higher elevations. -Slight (10-20%) chance of isolated mountain thunderstorms Monday PM from Highway 50 southward. -Primarily dry weather then expected to follow as periodically breezy onshore flow develops late Monday-Tuesday. -Some uncertainty in upper level pattern late in the week, but current ensemble trends indicate further warming with areas of Moderate HeatRisk potentially returning by Friday. .Changes from previous forecast... -Brief periods of elevated fire weather conditions possible into the early week ahead prior to the transition to onshore flow. && .AVIATION... VFR conditions persist at TAF sites next 24 hours with north to west winds expected to remain breezy to gusty as well. Strongest winds through the Valley and Delta gusting 25 to 35 kts at times, gradually decreasing after 15z Sunday. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 AM PDT Sunday for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF- Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Northern San Joaquin Valley in San Joaquin and Stanislaus Counties Below 1000 ft-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. && $$