THIS AVALANCHE ADVISORY EXPIRED ON March 10, 2018 @ 7:01 am
Avalanche Advisory published on March 9, 2018 @ 7:01 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

St. Regis Basin/Silver Valley

bottom line

The storm that was called off ended up materializing with 6 -8" of heavy, dense snow and gusty SW winds. Watch for windslabs and storm slabs at the high elevations, and windslab development to continue throughout the day. Expect to see loose-wet avalanche activity in the lower elevations today and on the southern aspects as the sun hits them tomorrow.  

How to read the advisory

St. Regis Basin/Silver Valley

How to read the advisory

The storm that was called off ended up materializing with 6 -8" of heavy, dense snow and gusty SW winds. Watch for windslabs and storm slabs at the high elevations, and windslab development to continue throughout the day. Expect to see loose-wet avalanche activity in the lower elevations today and on the southern aspects as the sun hits them tomorrow.  

3. Considerable

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

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

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: Storm Slab
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At the higher elevations we recieved 6-8" of new snow with SWE in the 1.5" range.  This is dense storm snow that will add stress to the pack.  The sunny aspects had formed a sun crust that can act as a slippery bed surface for these storm slabs. As you are travelling in the backcountry, evaluate the storm totals in the areas you are playing in and test small slopes for bonding and stability before committing to more consequential terrain.  

Avalanche Problem 2: Wind Slab
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Previous windslabs had stabilized nicely just in time for the new ones that formed late yesterday and through the night.  With a rain/snow line that waivered from 4000 to 5000 ft throughout yesterday and the night, expect the windslabs to become larger and more reactive the higher you get on the ridges where the snow was of lower density. They will continue to form on leeward terrain today as we recieve more snow accompanied by winds that are forecasted to gust up to 50 mph.  Shooting cracks in the snow is a sign of instability as you are skinning over windloaded terrain. 

Avalanche Problem 3: Loose Wet
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Warm temperatures and a high rain line will increase the risk for wet slides below treeline.  Expect to see evidence of loose wet slides and pinwheels.  Keep track of your elevation and where you are seeing rollerballs and expect the wet slide risk to increase and travel upwards in elevation as we hit the sunny days tomorrow and Sunday. 

recent observations

March usually likes to be complicated weather wise and this weekend will be no exception.  Yesterday we travelled to Latour Baldy and Frost Peaks area and enjoyed generally stable conditions. The windslabs from the last several storms have stabilized, and new slabs were just starting to form at the end of the day.  As we were leaving for the day, the snow had picked up and the winds with it.  We started seeing rollerballs around 5200' and were solidly in the rain line by 4500'.  And then a sleeper of a storm hit overnight.  Yesterdays snowpack is is now being burdened by new, dense snow and windslab development.  It came in warm and cooled down overnight, so the storm was right side up and should generally bond well.  But...the high elevation northerly aspects, we had a lighter density layer sitting on the surface which is now buried as a potential weak layer. On the southerly aspects, we had a sun crust which is now a possible slick sliding surface. The big take away is changing conditions with elevation and aspect; keep your head on a swivel as you are travelling in the backcountry this weekend and expect changes as the weather changes as well.  It's also worth a mention that the persistent weak layer is buried more than a meter deep in lots of locations. It is important to remember that it is still there when making terrain choices. It is low probablility that it gets triggered, but very high consequence.  

Weather and CURRENT CONDITIONS
Weather observations from the Region
0600 temperature: 27 deg. F.
Max. temperature in the last 24 hours: 35 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 30 mph
New snowfall in the last 24 hours: 6-8 inches
Total snow depth: 83 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Breezy, rain/snow likely then slight chance of snow Mostly clear Sunny
Temperatures: 40 deg. F. 26 deg. F. 43 deg. F.
Wind Direction: W W E
Wind Speed: 16-24 5 light
Expected snowfall: <1 in. 0 in. 0 in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Snow showers and windy then chance snow showers and breezy Decreasing clouds Sunny
Temperatures: 33 deg. F. 23 deg. F. 26 deg. F.
Wind Direction: W W E
Wind Speed: 28 -33 (G50) 7-11 3-5
Expected snowfall: 2-4 in. 0 in. 0 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.