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Explainer: What is a Snow Squall Warning?

Snow Band
Snow Band
Posted at 9:41 AM, Feb 18, 2020
and last updated 2020-02-18 11:44:41-05

MISSOULA — The National Weather Service issued a Snow Squall Warning for a portion of Missoula and Granite counties on Sunday night. If a Snow Squall Warning sounds unfamiliar, there's a good reason for that.

If your phone blew up shortly after 8 p.m. on Sunday you’re not alone, “at 8:15 p.m. our office issued a Snow Squall Warning,” explained National Weather Service Meteorologist Dan Zumpfe. That’s when a pocket of heavy snow began falling along the I-90 corridor between East Missoula and Nimrod.

A Snow Squall Warning is a new product the Weather Service put in place last winter.

A squall develops when a plume of moisture meets cold air.

“We combine the northwest flow with cold air aloft forcing the air up the terrain from the northwest tends to make the snow more intense and cause all sorts of havoc with heavy snow, but then exclude areas that are only several miles away to the north or south,” Zumpfe said.

A case and point was a persistent snow band from north of Lolo south into Florence produced about 6” to 8” inches of snowfall in a short amount of time, meanwhile 12 miles south of Florence in Stevensville -- not so much.

Snow Band
A persistent snow band from north of Lolo south into Florence produced about 6” to 8” inches of snowfall in a short amount of time, meanwhile 12 miles south of Florence in Stevensville -- not so much.

Zumpfe says despite ever increasing weather model capability, they have yet to master predicting exact locations snow squall development.

“We look at this in terms of how long they last, and how long it takes for them to develop, and our weather models right now are not capable of capturing what would be on the order of one or two hours where it would be very heavy, and then have no snow at all,” he explained.

What we do know is that there are areas that are more prone to squall development than others, but it doesn’t really eliminate any locations in western Montana.

“These bands tend to develop most along the I-90 corridor from Lookout Pass east to roughly Drummond and then from north to south about Arlee and then south to the ventral Bitterroots, so Stevensville. Maybe even Hamilton at times,” Zumpfe told MTN News

Until technology catches up with accurately forecasting snow band locations, it’s a good idea to pay attention when your phone goes into a frenzy when a Snow Squall Warning is issued, knowing that heavy snow, creating a travel nightmare may be nearby.

The Missoula National Weather Service Office has only issued a handful of Snow Squall Warnings since the product has been put into use.