THIS AVALANCHE ADVISORY EXPIRED ON March 24, 2018 @ 6:50 am
Avalanche Advisory published on March 23, 2018 @ 6:50 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

St. Regis Basin/Silver Valley

bottom line

The buried surface hoar layers from the past two weeks are starting to become active with the new, heavy loading we are getting.  Watch the temperatures and keep an eye out for rollerballs; the potential for wet slides will increase throughout the day as the temperatures goes above freezing at lower elevations or the sun peaks through. Also watch for isolated pockets of windslabs that formed late last night and expect more to form throughout the weekend.

How to read the advisory

St. Regis Basin/Silver Valley

How to read the advisory

The buried surface hoar layers from the past two weeks are starting to become active with the new, heavy loading we are getting.  Watch the temperatures and keep an eye out for rollerballs; the potential for wet slides will increase throughout the day as the temperatures goes above freezing at lower elevations or the sun peaks through. Also watch for isolated pockets of windslabs that formed late last night and expect more to form throughout the weekend.

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: Persistent Slab
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Two buried surface hoar layers are creating weak interfaces in the upper snowpack and being reactive in pit tests.  These are widespread on the NE -N-NW aspects, but expect to find pockets buried in shaded and protected locations on other aspects.  The upper one is between 5 to 12 inches down and the lower one is buried between 15 and 20 inches below the surface.  Expect these to become more reactive as more loading stresses them over the course of the weekend.  The early February is also still down there in some locations, although hasn't had any reports of being reactive in two weeks now.  

Avalanche Problem 2: Loose Wet
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The precipitation did turn over to snow in the night and the temperatures dropped to below freezing at elevation locking up the upper snowpack. Watch throughout the daytime as temperatures increase to above freezing at the lower elevations or the sun does come out for a while. It doesn't take much solar radiation to turn a stable surface into an unstable one. And while these surface wet loose slides are likely to be small in nature, it has the potential to step down as it gathers more weight traveling downslope and trigger the buried persistent weak layers.  

Avalanche Problem 3: Wind Slab
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In the night the rain turned into snow and the wind also picked up. Expect to see small windslabs that formed on the ridgetops and ridges on leeward terrain.  Expect more windslabs to form throughout the weekend as the next storm round comes in even colder and more windy. 

recent observations

Yesterday we travelled to the Cooper Pass/Glidden Pass area up Burke.  Rollerballs and wet slides were prevalent on all aspects and there was rain blanketing the area in the afternoon.  Stability tests were producing consistent failures for both the buried surface hoar layers, with more concern with the lower buried one.  The early February layer is still buried down there, well over a meter in the location we were at yesterday.  The concern with the buried surface hoar layers being so reactive in tests yesterday is that overnight we got more heavy precipitation and will continue to get more loading on top today and through Saturday and Sunday. It is up to you to dig down to see how much the rain influenced the pack last night and whether it changed these layers. I also expect more windslab formation with the storms coming in Friday night and Saturday.  Careful snowpack evaluation, cautious route-finding and conservative decision making are essential. 

 

Weather and CURRENT CONDITIONS
Weather observations from the Region
0600 temperature: 19 deg. F.
Max. temperature in the last 24 hours: 36 deg. F.
Average wind direction during the last 24 hours: WNW
Average wind speed during the last 24 hours: 7 mph
Maximum wind gust in the last 24 hours: 21 mph
New snowfall in the last 24 hours: 2-3 inches
Total snow depth: 79 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Mostly Sunny then Chance Snow Showers Snow Showers likely Snow showers then snow showers likely
Temperatures: 40 deg. F. 30 deg. F. 37 deg. F.
Wind Direction: S SE SW
Wind Speed: 7-13 6-8 11-15 (24)
Expected snowfall: 0 in. 1-2 in. 2-4 in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Chance Snow Showers Snow Showers likely Breezy. Snow Showers then snow showers likely
Temperatures: 29 deg. F. 24 deg. F. 28 deg. F.
Wind Direction: SW S SW
Wind Speed: 11-14 (G23) 10-14 17-24 (G24)
Expected snowfall: <.5 in. 2-4 in. 2-4 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.