A powerful storm packing soaking rain, gusty winds and mountain snow will chill the western United States from Wednesday to Friday.
The storm, which is more typical of November, will spread impacts from the Rockies to the Great Basin and Southwest.
Those with travel and outdoor plans across the region may encounter delays and disruptions during the second half of the week.
Heavy rain, mountain snow to cause travel hazards
Several days of heavy rain and thunderstorms could trigger flash flooding across parts of Montana, Wyoming, Idaho, Nevada, Utah and Colorado.
The heavy rain could wash out and close some area roads. Motorists should be prepared to take an alternate route.
Along with the heavy rain, some of the storms could produce damaging winds.
Thunderstorms will increase across the Southwest, following downpours and localized flash flooding from Paine early this week.
Total rainfall from this storm could surpass the average rainfall for the entire month of September in many places. This includes in Billings, Great Falls and Bozeman, Montana; Salt Lake City and Provo, Utah; Pocatello, Idaho; and Elko, Nevada.
As the rain pours across the lower elevations, snow will be possible across the higher terrain.
Snow levels will lower throughout the storm, ranging from 8,000 feet in the mountains of northwestern Wyoming to 10,000 feet in the mountains of Utah and northern Colorado, according to AccuWeather Senior Meteorologist Michael LeSeney.
"There may be enough snow in the highest passes Friday night to make roads snow covered and icy," LeSeney said.
Gusty winds to whip across the region
The strengthening storm will stir up gusty winds across the region from Thursday through Friday.
"Wind gusts through the high passes may reach 35 to 45 mph at times," LeSeney said.
Breezes will also kick up across the Southwest, where blowing dust could drastically reduce visibility for a time.
Motorists should keep a firm grip on the steering wheel while driving on area interstates.
Cool air to invade Northwest
Highs that were in the 70s and 80s F at the start of the workweek will be replaced with highs in the 50s and 60s in places such as Billings, Montana; Steamboat Springs, Colorado; Boise, Idaho; Flagstaff, Arizona; and Salt Lake City, Utah, to end the week.
Highs in this range are more typical of the middle to latter part of October.
"Thursday could be just a gloomy day across a part of the northern Rockies where the rain pours down and temperatures are held 10 to 20 degrees Fahrenheit below normal," AccuWeather Senior Meteorologist Kristina Pydynowski said.
In addition to an umbrella, a warm jacket may be needed to fight off the chill.
As the storm slowly pushes eastward, the threat for severe weather and flash flooding will shift into the central U.S. during the last weekend of September.