Heavy snow will be possible tonight across parts of western Montana as an arctic front approaches from the northeast. Low-lying areas in far western Montana, near the Idaho border will mostly see rain as the arctic front is likely to stall just to the east of Missoula. As the front moves through, gusty winds 15-25 MPH with gusts up to 40 MPH will be possible.
As the front moves through, rapidly falling temperatures may cause flash freezing of the roadways. This, in addition to the falling snowfall, will cause very hazardous travel conditions. Lows tonight will range from the upper teens to 20s in most areas. The exception will be the Bitterroot and Missoula Valleys, where lows will stick in the lower 30s.
WINTER STORM WARNING for the Flathead and Mission Valley from 4PM Saturday to 2AM Sunday for 1-3 inches of snowfall. The largest impacts are expected in the Flathead Valley. WINTER STORM WARNING for the West Glacier area from 2PM Saturday until noon Sunday for 4-7 inches of snowfall. WINTER STORM WARNING for the Butte/Blackfoot area from 5PM Saturday to noon Sunday for 2-5 inches of snowfall.
WINTER WEATHER ADVISORY for the Seeley Lake/Potomac region from 5PM Saturday to noon Sunday for 4-8 inches of snowfall. WINTER WEATHER ADVISORY for Gallatin County from 6PM Saturday to 5AM Sunday for 1-3 inches at low elevations and 3-8 inches in the mountains.
The Missoula and northern Bitterroot Valleys may see a brief period of snowfall late Saturday and into early Sunday. However, rain will be the primary precipitation type in this area as the arctic front will not make it far enough south and west to cause major impacts.
The front is expected to lift north through Sunday afternoon and evening, causing warmer temperatures and a transition back to rain for most western Montana valleys. The higher elevations will still see additional snowfall accumulations. Monday will bring additional chances of light rain and snow area-wide.