Northwest flow system to bring snow to Northern Rockies

A potent upper level disturbance arriving from the northwest will bring moderate to heavy snow to portions of the Northern Rockies from late tonight through Wednesday, favoring Western Montana, NW Wyoming, and Eastern Idaho.  Areas to see high impacts from this event include Missoula, Bozeman, and Jackson Hole.

This evening’s water vapor satellite image shows moisture from the advancing disturbance over the Pacific Northwest (image source: NOAA).

 

 

 

Snow will begin to fill into the region tonight with up to a few inches of snow expected across the valleys of Western Montana and Western Wyoming through daybreak tomorrow.  Cold air is in place ahead of this system, especially from Bozeman south to Jackson, and this will result in snowpacked roads for the morning commute on Wednesday.

The heaviest snow with this system is expected during the daytime hours Wednesday as the core of the disturbance and best upper level dynamics move across the area.  The RAP-model projected upper level heights and winds pattern illustrates this disturbance well as it moves across the Idaho/Montana/Wyoming region around midday Wednesday (image source: pivotalweather.com).

 

The next image shows the RAP Model’s projected snowfall (using the Kuchera method, which estimates snow-liquid ratios) from tonight through 5am Thursday.  While a single model’s snowfall projection can never be taken verbatim, it does give a general idea of snowfall amounts and distributions region-wide (image source: College of DuPage). 

We can see here that some of the highest snowfall totals with this storm are expected across the Bitterroot Range along the ID/MT border, the Gallatin and Madison Ranges in SW Montana, and the Teton Range in Wyoming.  This makes sense given the northwesterly storm track.

Here are some of the impacts expected across the area:

Missoula:  Most of the snow will fall between midnight tonight and mid-afternoon Wednesday with the heaviest snowfall rates between about sunrise and noon.  Snowfall will impact the morning commute with snow accumulating on roadways, while some melting is likely Wednesday afternoon as temperatures rise above freezing.  Snowfall amounts for Missoula are expected to be in the 3-6″ range, while in the surrounding mountain ranges totals in excess of one foot are possible.

Bozeman:  This pattern is favorable for significant snowfall amounts in the Bozeman area, with light snow filling in overnight and impacting the morning commute with cold temperatures in place.  However, the heaviest snow is expected from about mid-morning through early evening with road impacts expected throughout the day, including a challenging evening commute.  Total snowfall amounts are expected to be in the 4-8″ range for Bozeman, with amounts in excess of one foot across the surrounding mountain ranges.  Significant travel impacts are expected over the mountain passes, especially Wednesday evening.

Jackson Hole:  Steady snowfall will develop after midnight tonight and continue through about midnight Wednesday night.  Cold air will be locked in place across this region, yielding higher snow-liquid ratios and resulting in high impacts on the roads, both for the Wednesday morning commute and especially for Wednesday evening travel.  Total snowfall amounts will likely range from 3-6″ in the Jackson valley, with isolated higher amounts possible in the northern valley and near the base of the Tetons.  Snowfall amounts in the Teton Range could exceed one foot in some areas, with significant travel impacts expected over Teton Pass, especially Wednesday evening.  Gusty winds from the west could also create blowing/drifting snow, especially over mountain passes and across the open valleys of Eastern Idaho.

Idaho Falls/Pocatello:  Only light snowfall amounts are expected across this region, generally in the 1-2″ range.  However, strong winds can be expected Wednesday afternoon and evening, resulting in areas of blowing snow and poor road conditions. 

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