Red flag warning issued for Northern California’s interior as forecasts call for strong winds
The potential for fire danger from high winds and dry conditions have prompted a red flag warning for most of interior Northern California beginning Thursday night.
The National Weather Service issued the warning Tuesday morning, upgrading a fire weather warning issued the day before, as winds from the north known as Diablo winds are expected to kick up after a small weather system moves across the region.
Meteorologists said that the quick storm, which is expected to bring a brief chance for light rain Wednesday, would open the door to “critical fire weather conditions” through Saturday.
“The biggest concern with the main part of this system remains its track into the Great Basin,” the weather service’s Sacramento office said in a forecast discussion Tuesday. “This is a classic fall ‘Inside Slider’ pattern, which will bring gusty north to east winds and low daytime relative humidities through the end of the week.”
Diablo winds expected to kick up
Diablo winds, known in the south state as Santa Ana winds, are seasonal for autumn and move warmer air from Nevada and Utah into California, drying out grasses and creating conditions that could quickly spread fires. A lack of onshore winds from the Bay Area only contributes to the extreme conditions.
That was most notable in 2017 when a high-pressure system pushed dry winds from the Great Basin into the state, fueling the devastating wine country fires and the Santa Ana winds that fed a firestorm in Southern California.
The latest red flag warning will be in effect beginning at 11 p.m. Thursday for the majority of the Sacramento Valley and foothills, as well as the upper San Joaquin Valley, forecasters warned.
Winds could be strong, humidity poor
Wind gusts on the Valley floor could top 45 mph with sustained winds of 15 to 25 mph. The strongest winds, however, will be in the Sacramento-San Joaquin Delta where winds are expected to be 20 to 30 mph with gusts as high as 55 mph.
And the winds could push smoke from the Shoe Fire across the Valley, U.S. Forest Service officials warned in a separate news release. The fire in Shasta-Trinity National Forest has been burning since Oct. 9; crews reported Tuesday the fire had burned 3,420 acres and was 7% contained.
“As a result of these wind conditions, fire activity will increase and create greater smoke production,” firefighters said. “Residents and visitors (to the forest) will see and smell smoke. Heavy smoke conditions will likely linger in the greater Redding and north state area for several days.”
“Despite these weather changes firefighters on the Shoe Fire will remain safely engaged and aggressively continue to fight the fire,” they said.
Away from the fire, conditions on the ground won’t be much better: Forecasters said humidities would be 10% to 25% on Friday and Saturday with “moderate to poor” overnight conditions, allowing little recovery of moisture.
“The combination of gusty wind and low humidity can cause new fire starts and ongoing wildfires to rapidly grow in size and intensity,” according to the warning.
Temperatures in the area, forecasters said, should be at or near normal with Valley highs in the low to mid-80s and in the 60s and 70s in the foothills.
Long-range forecasts also suggest that a cooling trend from the onshore winds reappearing Sunday will bring more favorable conditions into next week.
What counties are covered?
The warning covers the following areas:
- Amador below 1,000 feet elevation
- Butte County, including the foothills above 1,000 feet
- Calaveras County below 1,000 feet
- Colusa County
- El Dorado County below 1,000 feet
- Glenn County
- Placer County below 1,000 feet
- Sacramento County
- San Joaquin County
- Shasta County, from Redding north through Shasta Lake
- Solano County
- Stanislaus County
- Sutter County
- Tehama County, including the foothills above 1,000 feet
- Yolo County
- Yuba County
The warning — in fire zones 213, 215, 216, 217, 218, 219 and 266 — remains in effect through 5 p.m. Saturday but the strongest winds are expected on Friday, forecasters said.
This story was originally published October 15, 2024 at 10:37 AM.
