Avalanche Advisory – 3/22/2014

THIS ADVISORY HAS EXPIRED.

Issued: March 22, 2014 at 7:00 a.m.
Valid Until: 11:59 p.m. of issue date

Good morning! This is Todd Hannan with the Flathead Avalanche Center avalanche advisory for Saturday, March 22, 2014. This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory will be Sunday, March 23, 2014.


MOUNTAIN WEATHER

WeatherGraphicHappy spring! Since the first day of spring we picked up between 5 and 14 inches of snow and mountain temperatures have remained below freezing in most locations. In the past 24 hours, we received up to 2 inches of new snow before showers tapered. Winds shifted out of the north and have been blowing 5-15 mph in most areas with 10-25 mph winds on the high ridges. Currently, remote weather stations and SNOTEL sites are reading -7 to 13 °F with north and east winds at 5-15 mph with gusts in the high 20s. Today will see partly cloudy skies becoming mostly cloudy with temperatures from the teens up to mid-20s. Winds should be light out of the southwest with the potential for isolated light snow showers.


RECENT OBSERVATIONS

RecentObservationsGraphicYesterday we rode into the Six Mile Peak area in the Swan Range. Though the areas where we traveled were more protected, we could see wind drifting the snow on adjacent high peaks (photo). We found 20-30cm of recent, unconsolidated snow from the previous 48 hrs. Temperatures remained cold through the day and the intermittent sun had minimal effect on the surface snow. We found the early March rain crust buried 70-80 cm deep and the snow above and below was fairly consolidated relative to the rest of the snowpack (photo). We found some instability within recent snow but were unable to propagate a fracture in any of our extended column tests (profile).  On Thursday, Erich was in the Red Meadow area in the Whitefish Range and found a layer that was able to propagate a fracture on the early March rain crust during several stability tests (observation) causing this layer to remain as a concern.

 On Thursday, BNSF avalanche safety reported 20-30 cm of new snow being transported onto east aspects along the ridgeline. The layer of greatest concern that they discovered in their snow profiles was an interface between a decomposing crust and a layer of weaker snow (observation).

General snow profile on east aspect in the Six Mile Peak area. Swan Range 3/21/2014

General snow profile on east aspect in the Six Mile Peak area. Swan Range 3/21/2014


Wind transporting snow on adjacent peaks. Six Mile, Swan Range. 3/21/2014

Wind transporting snow on adjacent peaks. Six Mile, Swan Range. 3/21/2014


Generalized image of upper snowpack highlighting the March 9 rain crust about 2-3 feet below the surface. Red Meadow, Whitefish Range. 3/20/2014.

Generalized image of upper snowpack highlighting the March 9 rain crust about 2-3 feet below the surface. Red Meadow, Whitefish Range. 3/20/2014.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


SNOWPACK DISCUSSION

Avalanche Problem #1

Wind SlabWith recent snow accumulations and strong winds earlier in the week, the potential exists to encounter recently formed wind slabs that are still reactive. Additionally, yesterday we observed north winds drifting snow along high elevation ridgelines potentially forming new wind slabs in the alpine zones on slopes that are typically windward. When travelling in high elevations, avoid wind loaded terrain steeper than 35 degrees, stick to lower slope angles, sheltered or scoured areas. Although care should always be taken when traveling around and approaching cornices, this time of year they can become particularly sensitive. Longer days with even short periods of more intense sun than they have been previously subjected to can make them unstable. Stay well behind confirmed solid ground when travelling above cornices and avoid travel below them.


Avalanche Problem #2

Persistent SlabSeveral layers within our snowpack pose a persistent slab and deep persistent slab threat that will likely plague us for the rest of the season. Though deeply buried and difficult to trigger, the late January/early February crust/facet layer still lurks in the snowpack. The possibility for avalanches to fail in these layers still exists if they are triggered in the right spot, specifically in areas notorious for harboring shallow snow like scoured areas or steep rocky terrain. The rain event that provided the trigger for that large avalanche cycle in early March formed a thick rain crust that now sits about 2-3 feet from the surface. Weak, moist snow has been observed below this crust and is also a concern. While we have yet to hear or observe any reactivity of this layer it cannot be ruled out as a potential persistent slab problem. The consequences of an avalanche breaking on these layers are high. Given the uncertainty of these deep slabs, it is best to avoid slopes where these layers exist or just avoid steep slopes altogether.

 


Oh, Spring in northwest Montana! Spring can bring a mixed bag of weather and snow conditions. It is not uncommon to have sun, snow, and rain in the mountains all in one day during this time of year. It is important to pay attention to rapidly changing conditions as weather can greatly affect snow and avalanche conditions. Pay particular attention to sun exposed slopes as the day progresses as well as rain on snow as wet avalanche conditions can change quickly.


BOTTOM LINE

For today, the overall avalanche hazard is MODERATE. This means that human triggered avalanches are possible, particularly on steep slopes and areas of shallow snow where deeper instabilities exist in the snowpack. Wind loaded slopes above 6500 feet and steeper than 35° are rated as CONSIDERABLE meaning that human triggered avalanches are likely in these areas.

Moderate_2

 Considerable

 

 


 

Note: The accuracy of the avalanche advisory becomes much more robust when we have more information. Thus, observations from all of you are extremely valuable to us. Even it is just a simple email saying “Hey, we found good riding in Mountain Range X, and observed no signs of instability or recent avalanches”. This type of information is just as important as observations of avalanches. The observations need not be formal, and can remain anonymous. Don’t’ worry, we won’t give away your secret riding/skiing spot either. Call us at 406.261.9873 or email us at fac.admin@flatheadavalanche.org. Thanks for your help.


See recent snow profiles as well as snow profiles from the entire season here.

Check out an interesting new research project that you can participate in about winter backcountry riding/snowmobiling and decision making from the Snow and Avalanche Lab at MSU. Details here.


DISCLAIMER

DisclaimerGraphic

This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.