Special Avalanche Advisory – 3/4/2014

ISSUED ON March 4 2014 at 7:00 am.

The Flathead Avalanche Center is issuing a Backcountry Avalanche Warning for the entire advisory area including the Whitefish Range, Swan Range, Flathead Range, and portions of Glacier National Park. New snow, rising temperatures, and strong winds have created highly unstable conditions. Natural and human triggered avalanches are likely.The avalanche danger is rated HIGH on all slopes in our advisory area. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended and avalanche runout zones should be avoided.

This warning will either be allowed to expire or updated by 7:00 a.m. on Wednesday, March 5.

Good morning! This is Erich Peitzsch with the Flathead Avalanche Center special avalanche advisory for Tuesday, March 4, 2014. This advisory applies only to backcountry areas outside established ski area boundaries.


MOUNTAIN WEATHER

WeatherGraphicA very moist and relatively warm system moved into the area Sunday and brought a substantial amount of new snow. In the past 24 hours we picked up between 2 and 6 inches of snow. However, the real concern is the snow water equivalent (SWE) this new snow contains. Up to an inch of SWE accumulated in the past 24 hours along with rising temperatures. Temperatures rose rapidly during the onset of this system.  Wind is currently out of the southwest at 10-20 mph with gusts to 40 mph. Currently temperatures are 25 to 31° F. Today, there is a slight break from intense precipitation, but we should see periodic surges of precipitation bringing up to another 6 inches of snow to the area. Tonight, another very moist system will begin to move through the area with rising snow levels. Stay tuned.


RECENT OBSERVATIONS

RecentObservationsGraphicThis is a storm where snow accumulation may not be as impressive as the amount of snow water equivalent (SWE). SWE of new snow is basically the weight added to the existing snowpack, and the mountains picked up a lot! Here is a summary:

Storm Totals: Since Sun. 3/2 at 4:00 a.m. (this represents settled snow on the ground)
Shed 7 (John F. Stevens Canyon): 13”
Noisy Basin (Swan Range): 1.5” SWE, 7” snow
Flattop Mt. (Glacier Park): 2.0” SWE, 14” snow
Stahl Pk. (Whitefish Range): 1.7” SWE, 12” snow
Pike Creek (Flathead Range): 1.8” SWE, 12” snow

The mountains also experienced a very rapid rise in temperature over the past 24 hours according to SNOTEL sites and remote weather stations. Many locations neared the freezing mark or went above that. This is just after being in the deep freeze (as low as -25° F on Sunday morning). 

BNSF avalanche safety reported widespread small to moderate sized natural avalanche activity yesterday in John F. Stevens Canyon (photos). These appear to be relegated to the new and old snow interface with depths up to 16 inches. On Sunday, I was in Canyon Creek in the Whitefish Range with an avalanche course. Our stability tests revealed a very reactive layer just below the melt-freeze crust that formed last Tuesday and Wednesday. We received no other observations yesterday. Todd is out today in the Flathead Range to see the effects of this new load.

A few feet of debris on Highway 2,  John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

A few feet of debris on Highway 2, John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

A crown of a natural avalanche along Highway 2,  John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

A crown of a natural avalanche along Highway 2, John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

A crown of a natural avalanche along Highway 2,  John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

A crown of a natural avalanche along Highway 2, John F. Stevens Canyon. 3/3/2014. Photo: BNSF Avalanche Safety.

 

 

 

 

 

 

 

 

 


 

SNOWPACK DISCUSSION

Avalanche Problem #1

Storm SnowGiven the forecast for continued new snow and wind, and rising temperatures the recent storm snow will still be an issue today. It is very likely you will trigger an avalanche today that involves the storm snow. Winds likely produced new and sensitive wind slabs as well.  Melt-freeze crusts near the surface with cold low density snow above will provide a smooth sliding surface for avalanches within new and recent storm snow. Keep in mind that the snowpack does not like rapid change, pay close attention to changing weather conditions such as rapid warming or increasing precipitation intensity.  For today, travel in and below avalanche terrain is not recommended.

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Avalanche Problem #2

Persistent SlabPersistent slab remains a concern particularly as we add a new load. The persistent slab on the mid-January crust with weak snow adjacent to the crust still poses a threat in many areas and is becoming a deep persistent slab. Additionally, there have been several recent observations of layers of weak faceted snow buried 2-3 feet down from the surface. Once initiated, a persistent slab has the ability to propagate long distances, change aspects, and wrap around terrain features. Remain vigilant in assessing slopes for persistent slab instabilities and be aware of the potential for smaller avalanches to step down into these deeper layers. Identifying persistent slab is only half of the battle, be thinking of how and in what areas you might be able to trigger them. Continue to avoid areas where triggering these deeper slabs is more likely, such as steep convex rollovers and in areas with shallow snow often found in steep rocky terrain or scoured areas. Without the obvious signs of instability such as shooting cracks and collapsing the only way to know what you are skiing or riding over is to dig into the snow.

 

 


BOTTOM LINE

For today the avalanche hazard is rated HIGH. Continued precipitation, strong winds, and rising temperatures, will cause very unstable conditions. This means that natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended.

 

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

Clicking on the avalanche problem icons provides a general definition for each specific problem.

Check our blog for a discussion about avalanche hazard ratings here.

New!!! Join us Feb. 12, 6:30 p.m. at Penco. We are working with the Flathead Snowmobile Association for the first in a series of motorized specific backcountry safety seminars. Details 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.


Observations are extremely valuable to us. If you’ve been out in the backcountry, please drop us a line with your observations at fac.admin@flatheadavalanche.org or call 406.261.9873. Thanks!


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.