BOZEMAN – We are still on track for a severe winter storm across Montana Saturday night into Sunday.
Forecast models continue to show a deep trough of Low-pressure building over the western US with warm moist air lifting to the NE at the same time colder Arctic air is dropping southward Saturday evening.
This is a classic overrunning pattern that can produce moderate to heavy snow. As the Low spins up into Yellowstone National Park Saturday the wrap around bands will be pushing up again the east side of the Continental Divide and Rocky Mountain Front. As the storm is forced to lift up the east of the of the mountains heavy snow is possible.
Forecast models show the area of greatest concern is from Lewistown to Helena to Great Falls up to Glacier National Park. The combination of 6”-12” of valley snow and wind gusts over 40 mph will produce blizzard like travel conditions. Higher mountains could see several feet of snow.
Locally, SW Montana will also experience areas of moderate to heavy snow on Sunday. However, we a different problem setting as these two airmasses collide. As the Low spins up into our region Saturday late afternoon to early evening surface temperatures will remain on the warm side. This means rain is possible between 6 pm and midnight Saturday for lower valleys. As the cold air digs in Saturday night rain will change to snow and with a rush of colder Arctic air by Sunday morning, flash freezing of wet roads are possible producing extremely icy roads.
Snow accumulations from the National Weather Service are in the 4”-6” for most lower valleys and mountains and passes up to or over a foot of snow. Gusty winds are likely at times and areas of blowing snow and reduced visibility are possible.
As of 1 pm Friday the National Weather Service has a WINTER STORM WATCH up for most of Montana Saturday night into Sunday evening. This watch will be upgraded Friday afternoon most likely to a winter storm warning. Look for updates here later this today.