THIS AVALANCHE ADVISORY EXPIRED ON December 19, 2018 @ 7:04 am
Avalanche Advisory published on December 18, 2018 @ 7:04 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

St. Regis Basin/Silver Valley

bottom line

The warm temperatures over the past couple days have helped the snowpack heal up quite a bit, especially at the mid and low elevations. There are still several lurking dragons buried at our upper elevations to be aware of.  Expect the avalanche danger to increase as this new storm arriving deposits a large amount of heavy, warm snow accompanied by strong winds.  Avoid riding on or below slopes steeper than 30 degrees until this snow has had time to adjust. 

How to read the advisory

St. Regis Basin/Silver Valley

How to read the advisory

The warm temperatures over the past couple days have helped the snowpack heal up quite a bit, especially at the mid and low elevations. There are still several lurking dragons buried at our upper elevations to be aware of.  Expect the avalanche danger to increase as this new storm arriving deposits a large amount of heavy, warm snow accompanied by strong winds.  Avoid riding on or below slopes steeper than 30 degrees until this snow has had time to adjust. 

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Storm Slab
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Mountain forecasts are calling for between 1' to 2' of new snow beginning this morning, with the snow/rain line rising to almost 5000' this afternoon.  This will be dense, heavy, wet snow that will form a thick storm slab adding significant weight to our pack.  Give it time to bond before you head out to terrain that is over 30 degrees. 

Avalanche Problem 2: Wind Slab
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Sustained winds in the 30's and gusts into the upper 40's (mph) are accompanying today's storm. Expect to see wind slab formation on leeward slopes.  

Avalanche Problem 3: Persistent Slab
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At the higher elevations, we have a couple of persistent weak layers that will continue to recieve a heavy loading over a short period of time.  The surface hoar that was buried with last weeks storm was still reacting in pit tests yesterday.  There are also a couple buried crusts that have facets associated with them.  We are also seeing depth hoar in areas where the snowpack is thinner.  Heavy loading, especially in thinner areas of the pack, will cause additional stress on these layers and be more likely to fail with the added weight.  Shallower avalanches have the potential to step down through the pack, creating a much larger avalanche.  

recent observations

Thank you to Silver Mountain Ski Patrol and the NSP Level 1 Avalanche Course for providing observations to help with today's forecast.  Below is a photo provided by Gabe White of the basal faceting. 

 

Weather and CURRENT CONDITIONS
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Tuesday Tuesday Night Wednesday
Weather: Rain Rain then rain/snow chance rain/snow
Temperatures: 41 deg. F. 33 deg. F. 37 deg. F.
Wind Direction: SW SW SW
Wind Speed: 13-17 14-17 8-11
Expected snowfall: 0 in. 0 in. 0 in.
For 4000 ft. to 6000 ft.
Tuesday Tuesday Night Wednesday
Weather: Heavy Snow and windy heavy snow and windy snow likely and windy
Temperatures: 33 deg. F. 26 deg. F. 28 deg. F.
Wind Direction: SW W SW
Wind Speed: 31-34, G48 29-33, G46 28-30, G40
Expected snowfall: 8-12 in. 5-9 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.