THIS AVALANCHE ADVISORY EXPIRED ON December 15, 2018 @ 5:29 am
Avalanche Advisory published on December 14, 2018 @ 5:29 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Fresh storm snow and strong southwest winds have created slabs on leeward slopes in high alpine terrain. Below tree line be alert to the possibility to trigger storm slabs in areas where this weeks storm snow is overlying a layer of buried surface hoar. Pay attention to changes as strong winds and additional snow are forecast Friday night into Saturday morning.

How to read the advisory

Fresh storm snow and strong southwest winds have created slabs on leeward slopes in high alpine terrain. Below tree line be alert to the possibility to trigger storm slabs in areas where this weeks storm snow is overlying a layer of buried surface hoar. Pay attention to changes as strong winds and additional snow are forecast Friday night into Saturday morning.

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: Wind Slab
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This past week brought a fresh dose of new snow that is available for transport with more snow and strong winds predicted for Friday night. Use caution in steep terrain(over 35°) on north and easterly aspects below ridgelines where this new snow has been loaded by the wind. Expect this problem to increase in danger and sensitivity by Saturday morning.

Avalanche Problem 2: Storm Slab
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This past week the mountains of the Kootenai Region recieved varying amounts of fresh storm snow across the area. Areas at treeline and above are where you will be most likely to encounter a storm slab problem. Below treeline the snowpack is not yet thick enough to cover up vegetation and is well anchored by brush and ground cover. Use caution in areas that are protected from the wind (steep openings in the timber) where surface hoar may have been preserved, shooting cracks and settling will be your first clues to its presence.

advisory discussion

This past week finally brought us a decent storm to kick off winter. If one takes a look at snotel sites across the area you will find that it came in relatively warm and left behind a highly variable amount of snow across the area. The western cabinets picked up around 16" since Tuesday while the Purcells gathered about 10" of new snow. Overall depths for the season also vary greatly with Bear mountain snotel holding about twice as much snowpack as Hawkins lake and Poorman creek. The take-home message here is that while you may find the potential to trigger an avalanche in the western cabinets below treeline you may have a difficult time finding enough snow to get off the road in the Eastern Cabinets or the Purcells. Hitting stumps and rocks may be your primary hazard in these areas! The brush and groundcover is not fully covered in these areas and will likely keep the snowpack anchored until we recieve another good shot of snow.

Yesterday we ventured into the Keeler-Rattle area. I was expecting to find touchy conditions with the new snow overlying buried surface hoar, I tried hard to find it; but, I didn't. I do think it is out there and I would assume it may be present until proven otherwise, especially in the Purcells where cooler temps are the norm. Pit results showed some weakness where the new snow is resting on the old snow interface, but it seems to be gaining strength with the help of moderate temperatures. We observed one natural avalanche crown that likely released on Wednesday on an easterly aspect below a wind-loaded ridgeline. The wind-slab problem is my main concern, particularly in the highest terrain above 6,500'. We have been under a strong south-westerly flow and the weather service is predicting more of the same.

Thanks for tuning in and feel free to email your avalanche observations to me at bbernall@fs.fed.us.  Any extra intel I can gather across the area helps!

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
410 AM MST Fri Dec 14 2018
DISCUSSION: A quick moving cold front will bring significant 
wind gusts and accumulating snowfall beginning late this evening
and continuing through Saturday morning. The heaviest amounts of
snow are expected along west facing slopes which will also bear
the brunt of the wind. The powdery nature of this snow will tend 
to bring dramatic reductions in visibility throughout open and 
exposed terrain and lead to highly transportable fresh snow. A
period of convective snow bands are possible around dawn Saturday
and continuing through mid-morning. The transient nature of these
bands make them hard to predict. But should they develop,
locations under these bands will be subject to heavy snow with
large dendrites.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           35%          85%          70%      
Hi/Lo Temps           32 to 38     19 to 25     24 to 31 
Winds(mph)            S 20G44      SW 30G57     SW 25G59 
Precip Chc            0            90           50       
Precip Type           none         snow         sno/shr  
Liquid Amt            0.00         0.24         0.07     
Snow Ratio(SLR)       0            13:1         16:1     
Snow Amt(in)          0            2-6          1-3      

Snow Level            3000         3500         1500     
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.

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