THIS AVALANCHE ADVISORY EXPIRED ON December 21, 2019 @ 6:43 am
Avalanche Advisory published on December 20, 2019 @ 6:43 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

St. Regis Basin/Silver Valley

bottom line

Heavy, dense snow as well as some rain hit the region last night on top of the lighter snow we recieved yesterday. This creates an upside down pack that will take time to stabilize, especially in shallower areas where there are buried persistent weak layers.  The winds have been steady so expect to find windloading as well.  

How to read the advisory

St. Regis Basin/Silver Valley

How to read the advisory

Heavy, dense snow as well as some rain hit the region last night on top of the lighter snow we recieved yesterday. This creates an upside down pack that will take time to stabilize, especially in shallower areas where there are buried persistent weak layers.  The winds have been steady so expect to find windloading as well.  

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Light dense snow yesterday was forming windslabs as we were travelling. Winds today at the ridgetops are predicted to be in the 30s and 40s, so even with denser snow falling, expect windslab formation to continue. Look for chalky, pillowy snow that is hollow sounding when you travel over it. Avoid these areas by sticking to less than 30 degrees. 

Avalanche Problem 2: Storm Slab
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We will continue to recieve snow throughout the day today, so expect the avalanche danger from storm slabs to increase as the day progresses.  As the dense, heavy snow stacks up, these will become more reactive. 

Avalanche Problem 3: Persistent Slab
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There are still pockets of buried surface hoar that were reactive in tests yesterday.  These could become more problematic as more weight is loaded on top.  They are predominantly located in sheltered areas, but the only way to know if they are in your location is to dig down and see.  At high elevations, the basal facets are widespread.  Their reactiveness depends on the snowpack depth and trigger points in the snow.  Once again, they require digging down to see what they are doing. 

recent observations

Yesterday in the Dominion Peak area we were finding the buried persistent weak layers that varied dramatically.  We'd do one test and they would release on only a couple taps and then a couple feet over they wouldn't release at all.  This variabilty is associated with the shallowness of the snowpack and is enough for me to be stepping back from bigger terrain: trigger points are everywhere out there right now.  There is tons of stuff on the ground than can create bigger "rotten" pockets under the snow. 

Another thing to consider today is the potential for wet avalanches.  The rain/snow line was around 5000 to 5500 last night and will remain there today.  As the snow gets saturated, heads up for rollerballs and pinwheels, which are signs of instability. 

 

Weather and CURRENT CONDITIONS
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Rain and Breezy Rain Rain
Temperatures: 42 deg. F. 37 deg. F. 41 deg. F.
Wind Direction: S SE SE
Wind Speed: 20-23 10-14 9-13
Expected snowfall: 0 in. 0 in. 0 in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Heavy Snow and Areas of Blowing Snow Snow and Patchy Blowing Snow Snow Likely and Windy
Temperatures: 34 deg. F. 35 deg. F. 35 deg. F.
Wind Direction: SW S S
Wind Speed: 38-44 31-33 26-31
Expected snowfall: 4-8 in. 1-2 in. 1-2 in.
Disclaimer

Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit.  For a recorded version of the Avalanche Advisory call (208)765-7323.