A WINTER STORM WARNING is in effect for most of central and western Montana through Friday into Saturday.
A WINTER WEATHER ADVISORY is in effect for the Helena Valley and parts of north-central Montana through Friday into Saturday.
A major storm will produce widespread snow across Montana over the next few days but accumularion will differ drastically from as little as a coating to as much as 40" in the mountains. This is a complicated storm with an arctic front coming in behind it, but the mountains will play a significant role. Not only will some of the highest terrain see snow measured in feet, the mountains will "shadow" the lower elevations including the Helena Valley down through Townsend significantly limiting snow accumulation. Then the track of the low will also leave some places out on the Hi-Line east of Havre through Glasgow will little snow. Snow will continue to increase through Thursday night in the mountains. Friday is when the weather really starts to go downhill. Widespread moderate to heavy snow will develop for most of the state. Highs will be in the upper 20s to the mid 30s. Several inches will fall through the day with the snow continuing into the night. The arctic airmass will slowly spill into the state from northeast to southwest through Friday night into Saturday. Saturday will be much colder with areas of lighter snow tapering off later in the day. Total snow accumulation will likely range from 6-12" in the lower elevations with as much as 40" in the mountains. Areas like the Helena Valley, north-central Montana and out the Hi-Line may see only a couple inches. Highs will likely top out in the 0s and 10s. That's not terribly cold but it will continue to get colder through Saturday night into Sunday. Sunday will be very cold with highs in the -0s and 0s. Overnight lows will drop down to between -10 and -20 with Sunday night being the coldest. A strong southwest wind will develop on Monday for the mountains and plains creating blowing snow. Temperatures will start to warm into the 10s and 20s. A weak system will produce scattered snow showers and a lot of wind on Tuesday, with highs in the 10s and 20s. Wind will continue to be strong over the plains on Wednesday will temperatures inching up farther into the 20s.
Curtis Grevenitz
Chief Meteorologist
