Recent dense snow formed shallow storm instabilities at mid and upper elevations. Evaluate storm totals before committing to steeper and larger terrain and be cautious around terrain traps. Lower snow totals and generally safer conditions exist at lower elevations.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Shallow storm instabilities could exist at mid and upper elevations from recent dense snowfall. New snow fell over a stout sun crust on sunny aspects and consolidated powder or an isolated surface hoar layer on shady aspects. Yesterday, my partner and I found good bonding between the new snow and multiple old snow layers in the northern Swan Range. Evaluate snow totals and test bonding with hand pits or smaller slopes before committing to steeper and larger terrain. Be cautious around terrain traps and look for surface cracks in the snow as a sign of instability.
The center of the snowfall universe was located in Noisy Basin during this last storm. Noisy received up to 8” of dense snow and over 1” of SWE while the rest of the forecast area received approx. 2-3” of snow and less than half an inch of SWE. Shallow storm instabilities could be found at mid and upper elevations where new snowfall buried a variety of old snow surfaces.
An observation on Wednesday highlighted isolated areas of surface hoar above 6000’ in the Whitefish Range and a recently buried surface hoar layer 6 to 12” deep on a few shaded slopes produced small but unexpected instabilities this past week in the Flathead Range (Example A, Example B). Watch for lens-shaped pillows below ridgelines and on steep convex or cross-loaded terrain where deeper snow depths could exist. Don’t get caught with your pants down and manage surface instabilities by evaluating storm totals and using hand pits or smaller slopes to monitor new snow bonding to the old snow surface. If we see periods of sunshine, expect surface conditions to change quickly possibly producing loose wet snow initiating from shallow snow areas, rocks, or vegetation entraining additional snow while moving downslope.
Don't miss out on our final avalanche education lecture this season at Whistling Andy Distillery in Bigfork. Thanks to all who participated in our avalanche education program this season and we're already planning next years line-up!
Clouds will persist over northwest Montana today with moisture staying to our south and west. The next weather system to impact our area moves through the region late Saturday and into Sunday. Widespread snowfall is expected with this system but models are still wavering on accumulations at this point in time. Winds are expected to remain light and transition from the south to the southeast over the next 36 hours with upper elevation temperatures ranging from upper 20's F to low 30's F.
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Mostly cloudy | Partly to mostly cloudy | Mostly cloudy with snow developing by evening |
| Temperatures: | 35 to 40 deg. F. | 18 to 23 deg. F. | 33 to 38 deg. F. |
| Wind Direction: | S to SW | SE | SE |
| Wind Speed: | 0 to 5 mph | 0 to 5 mph | 5 to 10 mph |
| Snowfall: | 0 in. | 0 in. | 0 in. |
| Snow Line: |
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
