THIS AVALANCHE ADVISORY EXPIRED ON March 21, 2016 @ 6:35 am
Avalanche Advisory published on March 20, 2016 @ 6:35 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Danger today is Moderate throughout the West Central Mountains.  Daytime temperatures near 50 degrees again today will make the possibility of small, loose avalanches on steep, sunny slopes increase as the snowpack begins to warm.  Skiers or snowmobilers may also be able to trigger lingering wind slabs on steep windloaded northerly terrain. Below 6000 feet, the danger is Low do to less new snow during the last storm cycle. 

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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We have been seeing some small, loose dry and loose wet slides and increasing roller ball activity on steep terrain over the last few days as the new snow started warming.  Pay attention today as the snowpack warms quickly on the solar aspects. Todays high temperature is going to be 10-12 degrees warmer than the last few day. you can probably expect to see even steep, shady aspects shedding some snow today.  Increasing roller ball activity is a sign of a warming snowpack and also a sign to avoid steep sun affected slopes. East facing slopes still hold the potential to release loose, dry and loose, wet avalanches as the morning sun heats the remaining new, soft snow up. Cornices should also be avoided right now as well. Large cornices have been failing as the  temperatures increase. Cornices are great bombs especially on windloaded slopes where they fall.  They can trigger large avalanches as they quickly overload the slope with their falling weight.  Travel on or below cornices is not recommended as the day warms.

Avalanche Problem 2: Wind Slab
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We are still seeing a lingering wind slab problem on steep, windloaded terrain.  The winds that accompanied the beginning of last week's storms transported a lot of snow.  Some of the windslabs are very dense and unlikely to be triggered right now but Wednesday and Thursday we were still seeing some areas of hollow or punchy windslab that was resting on loose, unconsolidated snow below.  Windslabs between a few inches and up to about 20 inches are still a concern if you are playing in the shady, northerly terrain. Your best bet for staying safe is to utilize good travel and play/riding techniques with only 1 person on a slope at a time. Keep your eyes on your partners if you are playing in the windloaded terrain and plan for an exit route if you do trigger one of  these windslabs. Large cornices should also be avoided as they have been breaking surprisingly big since last weekend and the warm temperatures are likely to make some of these fail naturally in the heat of the day.

recent observations

This photo taken in the Grassy Twins Basin was sent in yesterday.  The slide looks like it failed earlier in the week, possibly as temperatures warmed Wednesday after the last round of snow.  The crown of the slide is visible in the shady area and extends across lookers right above the upper cliff band.  Several small sluffs are also visible on the lower right hand slope where the snow is getting some early sun. The cornice formation from the last storm was substantial as you can see at the top of the shady gully.  These cornices are going to continue to fail throughout the spring and can put a large load on the snow when they do.  Lingering wind slabs or older weak layers from early in the season can be triggered when the cornices do fail. Great photo, thanks to Scott Marquart for sending it in.

 

weather

Today is going to be another unseasonably warm day with a high temperature near 50 above 7000 feet. Increasing clouds and South winds this afternoon will be the forerunners to the next storm system that will likely leave another 4-8 inches of snow by Wednesday morning.  Snowlines will start out near 6000-6500 feet tonight and Monday and decrease Monday night to the valley floors. 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: Mostly sunny, with a high near 52. Calm wind becoming south 5 to 8 mph in the afternoon. Showers and possibly a thunderstorm before midnight, then showers likely. Low around 33. South wind 5 to 7 mph becoming calm. Chance of precipitation is 100%. A chance of showers, then showers likely and possibly a thunderstorm after noon. Cloudy, with a high near 44. South wind 5 to 10 mph. Chance of precipitation is 70%.
Temperatures: 52 deg. F. 33 deg. F. 44 deg. F.
Wind direction: Calm, then South South South
Wind speed: Calm, then 5-8 5-7 5-10
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: A slight chance of rain and snow showers after noon. Mostly sunny, with a high near 47. Breezy, with a south southwest wind 14 to 21 mph. Chance of precipitation is 20%. Rain and snow showers. Some thunder is also possible. Low around 27. South wind 15 to 18 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible. Snow showers. Some thunder is also possible. High near 39. Breezy, with a south wind 14 to 20 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 47 deg. F. 27 deg. F. 39 deg. F.
Wind direction: S/SW South South
Wind speed: 14-21 15-18 14-20
Expected snowfall: 0 in. 1-2 in. 1-2 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center. This advisory covers the West Central Mountains between Hard Butte on the north and Council Mountain on the south. 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 at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.