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000 FXUS66 KSTO 141815 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1115 AM PDT Mon Sep 14 2026For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing.KEY MESSAGES
- Critical fire weather conditions through this afternoon due to gusty winds and low daytime humidity
- Red Flag Warning in place for portions of the Sacramento Valley and adjacent foothills until 5 PM PDT Today
- Precipitation Chances (10-25%) Wed-Thu for Shasta County, Coast Range, and Southern Cascades with nonzero thunderstorm chances (5-15%)
DISCUSSION
Today-Tuesday: The main weather highlight this morning is ongoing gusty north winds along the Interstate corridor around 15-30 MPH. These winds have generally peaked this morning and will gradually weaken through the afternoon and evening. Dry conditions are expected to continue this afternoon with Valley afternoon humidities in the teens. Given the combination of winds and low relative humidity, our Red Flag Warning remains in effect for portions of the northern & central Sacramento Valley and adjacent foothills until 5 PM this evening. Please be sure to continue fire safety practices and outdoor burning is not recommended.
After today, an approaching upper level low from the Pacific NW will bring a pattern change of cooler temperatures, increased moisture, and precipitation chances midweek. Valley highs on Tuesday will be in the upper 80s to low 90s and localized areas of RH in the northern Sac. Valley and eastern Central Valley foothills.
Wednesday-Saturday: First day of cooler weather with highs in the low to mid 80s in the Valley and upticks in humidity for several days. With this our aforementioned low may bring chances for isolated thunderstorms around the mountains of Shasta County and Southern Cascades, however current guidance keeps any activity further north and west. There is still some model uncertainty regarding exact location and intensity but pattern recognition points to most likely outcome of the bulk of shower/thunderstorms, if occurring, closer to the CA coast and further north than our forecast area. That being said, we will monitor to monitor and reevaluate any thunderstorm/lightning fire weather threats as we get closer! Currently, we have a 5-15% chance of thunder near the Coast Range with an 10-25% chance of wetting rains across the Shasta County and Southern Cascades mountains. Precipitable water forecast show limited support for any widespread thunderstorm development at the moment with dry forecast soundings across various sites as well, keeping fire weather concerns as minor impacts at this time.
Beyond Thursday, high pressure begins to develop again and will see temperatures rebound to near seasonable and dry conditions, particularly over the northern SAc. Valley, and breezy afternoon winds.
As always, be sure to follow the forecast at weather.gov/sacramento for any updates!
AVIATION
VFR conditions prevail across TAF sites and interior NorCal over the next 24 hours. North winds in the Central Valley gradually decrease this afternoon and become less than 12 kts after 00Z Tuesday. Period of breezy downslope winds in the mountains and foothills with gusts 15-20 kts from 03Z to 16Z Tuesday. Winds turn southerly after 18Z Tuesday with gusts 15-25 kts at times.
STO WATCHES / WARNINGS / ADVISORIES
Red Flag Warning until 5 PM PDT this afternoon for Butte County Below 1000 ft-Central Colusa County Incl. I-5-Central Glenn Co & Interstate 5-Eastern Colusa County-Eastern Glenn County- Glenn/Colusa Coast Range Above 3000 ft-N. Sac Valley in Tehama County-Shasta Metro-Sierra (Tehama-Plumas) 1000-3000 ft- Sutter/Yuba counties below 1000 ft-W. Glenn/Colusa Foothills 1000-3000 ft.