Avalanche Advisory – 4/2/2014

THIS ADVISORY HAS EXPIRED.

Issued: April 2, 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 Wednesday, April 2, 2014. This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory will be Saturday, April 5, 2014.


MOUNTAIN WEATHER

WeatherGraphic Yesterday saw partly cloudy skies with isolated light snow showers. Flattop Mountain SNOTEL site was the warm spot, with a high temperature of 42°F. Currently, remote weather stations and SNOTEL sites are reading 11 to 29 °F with winds out of the east at 3-5 mph. Today will see partly cloudy skies with temperatures from upper 20s to mid-30s. Light snow showers are possible this afternoon and winds will shift to 5-10 mph out of the west.

 


RECENT OBSERVATIONS

RecentObservationsGraphicYesterday Tony and I traveled into the Swede Creek drainage in the Whitefish Range. The snow surface on our ascent was a supportable melt-freeze crust on any aspect that was previously exposed to the sun. Temperatures remained relatively cool with a light breeze and intermittent clouds to keep the sun at bay. It wasn’t until late in the afternoon that the snow surface began to show signs of melting (photo). We observed some roller balls/pinwheels from steep, sun exposed slopes. In the shade, the snow remained dry and unconsolidated. A snow profile on a south aspect revealed multiple crusts in the upper snowpack that were minimally reactive to stability tests. In an area with a relatively shallow snowpack we found weak faceted snow near the ground.

Skiers in the Pike Creek drainage in the Flathead Range and in the Apgar Range last weekend encountered difficult travel conditions due to warm heavy snow and breakable crusts (observation). On Monday, skiers in the Marion/Dickey Creek drainages in the Flathead Range noted sun affected snow on solar aspects and surface snow that remained cool and dry in the shade (observation).

Glide cracks are beginning to rear their ugly heads again this spring. Erich noted a couple of glide cracks last Friday in the Swan Range (photo), and Glacier National Park rangers noted a few in the park.

Large cornices along ridgeline. Notice small woodland creature ignoring safe travel protocol around cornices. Swede Creek, Whitefish Range. 4/1/2014

Large cornices along ridgeline. Notice small woodland creature ignoring safe travel protocol around cornices. Swede Creek, Whitefish Range. 4/1/2014


Roller balls on steep slopes indicate that surface snow is starting to become wet. Swede Creek, Whitefish Range. 4/1/2014

Roller balls on steep slopes indicate that surface snow is starting to become wet. Swede Creek, Whitefish Range. 4/1/2014


An early sign that snow surface is becoming moist.  Swede Creek, Whitefish Range. 4/1/2014

An early sign that snow surface is becoming moist. Swede Creek, Whitefish Range. 4/1/2014

 

 

 

 

 

 

 

 

 

 

 

 


SNOWPACK DISCUSSION

Avalanche Problem #1

WetAvalGiven the time of year with longer days and increasing sun intensity, pay close attention to the effects of warming and direct sun on the snow surface. Today the wet avalanche hazard should be confined to slopes that receive prolonged direct sun exposure. Consider moving to a shaded aspect if the snow surface becomes wet and surface crusts begin to melt. Avoid steep sun exposed slopes, particularly when traveling in or above terrain traps.

 

 


 

Avalanche Problem #2

Wind SlabWind slabs can take up to a week to gain strength. Moderate to strong winds last weekend formed sensitive wind slabs and though they are moving in the direction of stability, steep wind loaded slopes should still be treated as suspect. Pockets of recently formed wind slabs were deposited on top of layers of graupel, and though this is not considered a persistent weak layer they can take a bit longer to gain strength. It remains important to assess the stability of each slope you intend to ski or ride. Additionally, large cornices exist in the area (photo), and with warming temperatures this time of year they can become particularly sensitive. Even short periods of more intense sun can make them unstable. Give cornices a wide berth when traveling above them and avoid travel below.

 


Avalanche Problem #3

Deep SlabIt’s getting late in the season, spring is in the air, and we have been talking about deep persistent slab for months. We continue to find areas with shallow snow that harbor weak snow near the ground, as well as the thick rain crust from early March. Neither of these have been recent players, but the consequence of triggering an avalanche in these deep slabs remains high. Prior to committing to a slope ask yourself, “where would I be most likely to trigger a deep slab?” More often than not, the answer will be on that steep rollover or in areas notorious for having a shallow snowpack like near those exposed rocks. Don’t let your guard down when assessing for deep slab instabilities and continue to avoid terrain with the highest probability of triggering these slabs .

 


 

Spring can bring a mixed bag of weather and snow conditions. It is important to pay attention to rapidly changing conditions as weather can greatly affect snow and avalanche conditions this time of year. Pay particular attention to rapidly rising temperatures or extended periods of direct sun exposure.

 


BOTTOM LINE

For today the avalanche hazard is LOW below 5500 feet. This means that human triggered and natural avalanches are unlikely, however normal caution and safe travel practices should still be exercised.  Terrain above 5500 feet is rated as MODERATE, human triggered avalanches are possible, particularly on slopes steeper than 35 degrees that have a shallow snowpack. 

 

Moderate_2

Low 


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