THIS AVALANCHE ADVISORY EXPIRED ON February 18, 2016 @ 7:15 am
Avalanche Advisory published on February 17, 2016 @ 7:15 am
Issued by Dave Bingaman - Payette Avalanche Center
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The avalanche danger is CONSIDERABLE today on steep, solar aspects which have the possibility of producing natural wet/loose and wet slab avalanches as an already warm snowpack warms throughout the day. Northern aspects will have MODERATE avalanche danger where human caused avalanches are possible in the upper 4-20 inches of the snowpack. Slopes over 35 degrees should be avoided until the snowpack refreezes. 

 

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Loose Wet
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Steep slopes will have the possibility of producing natural avalanches, especially slopes on the Southern half of the compass if the sun pops out periodically through the day.  These slides are mainly point releases that could pick up momentum in the warm snow, you will see the debris on all steep slopes right now. We saw debris on almost all aspects yesterday.  Temperatures have stayed above or just near freezing for a couple of days in a row now and the snowpack is disintegrating.  Even on some shady northerly slopes the surface resembles a melting snowcone. Temperatures dipped just below freezing last night but not enough to refreeze the snowpack. We probably wont see a good freeze until tomorrow night.  

Avalanche Problem 2: Persistent Slab
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Triggering a slab due to this weak layer has become more difficult over the last two weeks, but I would not let my guard down, We are still finding this weak layer in upper elevation wind protected terrain. Pit results and stability testing are pointing toward less likelihood of triggering, but if triggered we are still talking about a potentially unsurvivable hard slab avalanche. Take the time to carefully assess terrain choices on the north half of the compass today. Especially areas where the snow cover is thinner which allows the buried surface hoar to be closer to the surface, and in turn more reactive---especially for snowmachines. This is the same layer that was the cause of the fatal avalanche on January 31st. A persistent weak layer such as this is a low probablility, but HIGH CONSEQUENCE scenario.  In addition, the old snow layer around 55cm is still showing signs of instability in our pit tests with moderate test scores.  This layer is comprised of grauple in some areas and has buried Surface Hoar and fine grained facets mixed in in other areas.

recent observations

We traveled out the Goose Lake Rd yesterday in the Lloyds Lake area and into the some of the steeper terrain in the Hard Creek drainage. Widespread wet/loose activity and a very wet snowpack are what we found.  We also saw one good sized natural avalanche in a very steep NW facing couloir above Hard Creek. From our vantage point above it looked like a point release or loose/wet that turned into a wet slab as it gained momentum and debris.  We also found the December Surface Hoar buried and fully intact on a shady, Northern aspect at 7300 feet buried down around 100cm/ 40 in.  This is the layer that was responsible for the January 31 fatality near Twin Lakes. All of the steeper terrain that we saw yesterday on all aspects has been shedding roller balls and wet/loose debris to the point that it is going to take a while to cover up the debris once we do get back to normal temperatures and resume our winter.  Skiing is challenging with a variety of thin crusts and very warm, sticky snow as the day warms. Snowmobiles will find soft, somewhat carveable snow and relatively easy travel on all aspects.

weather

Look for increasing clouds,scattered snow and rain showers and increasing S/SW winds through the day today as a low pressure system works its way over our area.  Temperatures will slowly drop over the next few days but will remain above average.  Tomorrow will be cooler with 5-10 inches of snow forecasted through Thursday night.  Winds are going to be steady in the 20-30 range with gusts close to 50 mph. Friday shows a return to above average temperatures with a chance of scattered snow in the mountains and rain in the valleys through the weekend. Decreasing low temperatures in the mid to lower 20's will help the snowpack refreeze and begin to heal but daytime highs will be climbing into the slush zone again as we head into next week.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: A 30 percent chance of showers after 11am. Mostly cloudy, with a high near 43. Calm wind becoming south southeast 5 to 8 mph in the afternoon. Rain likely, mainly after 11pm. Cloudy, with a low around 35. South southeast wind 5 to 8 mph. Chance of precipitation is 70%. Rain before 11am, then snow. High near 36. South wind 7 to 14 mph. Chance of precipitation is 100%. New snow accumulation of around an inch possible.
Temperatures: 43 deg. F. 35 deg. F. 36 deg. F.
Wind direction: S/SE S/SE S
Wind speed: 5-8 5-8 7-14
Expected snowfall: 0 in. 0 in. 1 in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: A 30 percent chance of snow showers after 11am. Mostly cloudy, with a high near 44. Windy, with a south southwest wind 18 to 23 mph increasing to 27 to 32 mph in the afternoon. Winds could gust as high as 47 mph. Total daytime snow accumulation of less than a half inch possible. Snow, mainly after 11pm. Low around 31. Windy, with a south wind 26 to 34 mph, with gusts as high as 50 mph. Chance of precipitation is 90%. New snow accumulation of around an inch possible. Snow. Temperature falling to around 22 by 1pm. Breezy, with a south southwest wind 22 to 28 mph, with gusts as high as 41 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 44 deg. F. 31 deg. F. 22 deg. F.
Wind direction: S/SW S S/SW
Wind speed: 18-23, Gusts to 47 26-34, Gusts to 50 22-28, Gusts to 41
Expected snowfall: Trace in. Trace in. 3-5 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.