THIS AVALANCHE ADVISORY EXPIRED ON February 23, 2016 @ 6:23 am
Avalanche Advisory published on February 22, 2016 @ 6:23 am
Issued by -
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The avalanche danger is MODERATE at upper and middle elevations today. Snowfall and southwest, south, and southeast winds formed slabs in high elevation terrain at the end of last week. It remains possible to trigger a soft or hard windslab in exposed terrain. In very steep, sheltered terrain, sun and human caused loose snow avalanches are possible. Below 6,000 feet the avalanche danger is LOW.

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Winds out of the south, southeast and southwest hammered the West Central Mountains through the second half of last week. Wind gusts were in the 40-60 MPH range on the higher peaks and ridges with sustained winds in the 20+range. The avalanche danger on wind loaded upper elevation terrain is enough to merit conservative terrain choices on all wind affected slopes. These strong winds have done a great job loading and crossloading slopes on east, north and west facing aspects as well as loading slopes below rocky or steep headwalls well below the ridgetops.  Windslabs range from very stiff to soft today and from a few inches to over a foot thick. Some of these windslabs formed on the crusts that developed during our last high pressure. Look for clues like cracking and collapsing as well as other obvious signs of windslab like a textured or scalloped snow surface or pillows and drifts as you are moving through the mountains today.  Additional snowfall on Friday evening also did a great job camouflaging some of these obvious clues so pay attention to the way the snow feels as you travel today, if you encounter a hollow, punchy, or drummy feeling snow surface you are on windslab.  Snowmobiles may have more of an affect on these slabs than skiers where they are more dense or firm. Wind slabs often let you get well out on to them before you are able to trigger them trapping you in the middle of the slab when it is triggered. 

Avalanche Problem 2: Deep Slab
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The pesky New Year's buried surface hoar still lingers deep in our snowpack. It is located mid-slope on northwest through east aspects above 7,000 feet and will most likely be with us for the rest of the snow riding season. Pit results and stability testing point 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 and throughout the rest of the season. This layer is especially dangerous in 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,deep weak layer such as this is a low probability, but HIGH CONSEQUENCE scenario.  

advisory discussion

Thanks to everyone who came out Friday night for the Backcountry Film Festival. We had over 100 people turn out for what ended up being some great short films. Kudos to the Valley County community for your continued support of winter recreation programs!

recent observations

PAC forecasters spent the morning yesterday helping McCall Fire and Rescue with a mock avalanche rescue. It was a great learning experience for all involved and we thank the department as well as Tamarack Ski Patrol for involving us in this life saving training.

We had a report of a decent sized natural avalanche near Marge Lake on Friday but didn't hear or see of any more avalanche activity over the weekend.  If you do trigger an avalanche or see avalanche activity, please take the time to send us a short report and a photo with as much of a description as possible.  You can email avalanche info to us at: forecast@payetteavalanche.org or plug it into our Observations page on the website . Your help is greatly appreciated!

weather

West -northwest winds at 5-10 mph will keep temps a little cooler in the mountains today than they have been. Should be partly sunny with highs in the 20's. The rest to the week looks to be sunny, except for a weak shortwave disturbance on Wednesday that should only result in high clouds. Models are trending towards a pattern change for the weekend with a long wave trough moving inland from the pacific. However, models are in disagreement with the timing and placement of precipitation.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Isolated snow showers after noon. Partly sunny, with a high near 36. Calm wind becoming west northwest 5 to 8 mph in the afternoon. Chance of precipitation is 20%. Partly cloudy, with a low around 10. Northwest wind 5 to 8 mph becoming calm after midnight. Sunny, with a high near 35. Calm wind becoming south around 5 mph in the afternoon.
Temperatures: High 36 deg. F. Low 10 deg. F. High 35 deg. F.
Wind direction: West-northwest Northwest South
Wind speed: 5-8 5-8 5
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Scattered snow showers, mainly after 11am. Partly sunny, with a high near 28. North northwest wind 7 to 11 mph. Chance of precipitation is 30%. New snow accumulation of less than a half inch possible. Partly cloudy, with a low around 12. North northeast wind 7 to 14 mph. Sunny, with a high near 32. Light and variable wind becoming south southwest 10 to 15 mph in the morning.
Temperatures: High 28 deg. F. Low 12 deg. F. High 32 deg. F.
Wind direction: North-northwest North-northeast South-southwest
Wind speed: 7-11 7-14 10-15
Expected snowfall: Less than half inch in. 0 in. 0 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.