THIS AVALANCHE ADVISORY EXPIRED ON January 16, 2019 @ 5:19 am
Avalanche Advisory published on January 15, 2019 @ 5:19 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Last weeks warm temperatures and rain were followed by high pressure and cooler conditions. This combo has effectively set us up for stable snowpack conditions in the short term. Expect this to change by Thursday as more snow moves into the area and falls on a layer of growing surface hoar and thick rain crust. Continue to keep an eye out for potential trouble spots in extreme terrain and areas of thin snow at the highest elevations.

How to read the advisory

Last weeks warm temperatures and rain were followed by high pressure and cooler conditions. This combo has effectively set us up for stable snowpack conditions in the short term. Expect this to change by Thursday as more snow moves into the area and falls on a layer of growing surface hoar and thick rain crust. Continue to keep an eye out for potential trouble spots in extreme terrain and areas of thin snow at the highest elevations.

1. Low

?

Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

?

Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

?

Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The persistent slab problem that we have been discussing is unlikely to move at this point without a drastic weather change. Below 5,500' it is very much "bridged" by a thick rain crust. Above this elevation I would continue to use caution in extreme terrain and continue to practice safe travel habits as there is always potential to find a weak spot and trigger one of these weaknesses.

advisory discussion

Yesterdays' travels took us up an easterly aspect up to 7,000' in the Cabinet Mountains. Pit results on the easterly aspect were fairly uneventful with some failures in the top 12" of snow between crust layers and none showing the likelihood to propagate. Still finding facets at the base of the snowpack in thinner areas but they continue to show progress and gain strength.  Another pit done on a north aspect at 7,000' revealed no weaknesses in the upper snowpack and showed a nice progressive density increase with increased depth "right side up!" We observed a couple of small crowns and older wet slides that likely released during last Thursdays rainy and warm weather. No slides were observed yesterday despite the abundance of sunshine at upper elevations.

The real story right now is what may come in the future. With the current high pressure and temperature inversion we are under there is an abundance of surface hoar growing on all aspects that we observed up to 6,000', I believe it is likely you may find it at higher elevations in other locations; but, it seems with the upper elevations recording warmer temps, the growth of surface hoar is likely stunted and less prevalant. Below 5,500' this surface hoar is growing on a thick, hard rain crust, this will be a significant issue once it begins to snow.  It is really the perfect recipe for creating touchy avalanche conditions at lower elevations that may take some time to heal. So, with the current stable conditions expect the potential to undergo a big change by the weekend at treeline and below. Watch the video below for a quick summary of yesterdays observations.

https://youtu.be/ZyBn8QEzXSw



Surface hoar crystals .5-1cm in length

 

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
410 AM MST Tue Jan 15 2019

DISCUSSION: A cooling trend is being observed in the high
elevations, that will continue through today. Moisture is also
increasing; weak waves of moisture will promote light snow out of
existing stratus. Light snow arrives to the high terrain by this
evening with minor accumulations. Models remain on track for a
long duration snow event Thursday and Friday with easterly winds.
48 hour snow totals currently range from 6-8 inches with SWE
0.30-0.50 inches.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           35%          55%          65%      
Hi/Lo Temps           28 to 34     12 to 19     26 to 31 
Winds(mph)            E  7         E  6         E  6     
Precip Chc            0            30           30       
Precip Type           flurries     snow         snow     
Liquid Amt            0.00         0.01         0.02     
Snow Ratio(SLR)       11:1         19:1         17:1     
Snow Amt(in)          0            0            0        

Snow Level            2000         1500         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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