THIS AVALANCHE ADVISORY EXPIRED ON January 27, 2016 @ 6:48 am
Avalanche Advisory published on January 26, 2016 @ 6:48 am
Issued by George Halcom - Payette Avalanche Center
bottom line

Today, the avalanche danger is Moderate on wind-loaded slopes in upper and exposed middle elevation terrain. Moderate danger means it is still possible for skiers or riders to trigger freshly formed wind slabs in exposed terrain, and or trigger our persistent slab (buried surface hoar) that exists in random locations that were protected from the wind. At middle elevations, the wind slabs are smaller and less wide spread. Low elevations below 6,000 feet the 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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Wind slabs continue to be a problem in the upper elevations. The mountains picked up another 8-12 inches in the last 48 hours wth some moderate SW winds.You are most likely to find these slabs at or near the ridgetops or in exposed terrain above 7,000 feet. They are still relatively widespread in the upper elevations and range in sensitivity from easily triggerable to resistant. They also range in size from a few inches to a few feet in some areas. New snow over the last few days has also done a great job camouflaging some of the wind slabs formed last week, so you may not see any visual clues until it is too late. These slabs range in density between soft to hard, which means they may let you get well out onto them before they fail.  Also, some of these wind slabs may be resting on a layer of faceted snow or surface hoar that was buried last week which may allow them to release deeper still.  Your best bet until our snowpack begins to 'heal' is to avoid skiing or riding on or below steep, wind loaded slopes.

 

 

  

Avalanche Problem 2: Persistent Slab
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A weak layer, Surface Hoar, was buried 2 weeks ago and began producing natural and human triggered avalanche activity in sheltered terrain in the northern half of the PAC advisory area. This layer has been slowly covered, and has failed in some areas, and is still waiting for a trigger in other places. Buried surface hoar and faceted snow have the ability to propagate over large areas when they fail and are responsible for most avalanche incidents and fatalities.

The photos below show the depth of the buried surface hoar where we have found it in our test pits. It is collapsing and failing in the moderate to hard range right now(CT scores 16-18, ECTP 18-22). The slab overlying this layer has become very cohesive due to the recent warming temperatures. If you were to unintentionally trigger and get caught in an avalanche in these conditions it would not be pretty. Because of the random distribution of this weak layer,  and the strength of the overlying slab it is very hard to predict exactly where you will trigger it. If you are looking to play it safe, stick to slopes below 30 degrees today.

NNW aspect, intentionally triggered avalanche from Friday 1/22/16

 

 

Photo and crown profile of intentionally triggered avalanche (ski cut) from Friday. Weak layer is visible as thin gray line near bottom of picture.

advisory discussion

Upcoming Events: Click the EDUCATION tab above for more details on all PAC educational events.

Out of Bounds Safety | 01/30/2016 |

Introduction to avalanche awareness for out of ski area backcountry use. The close proximity to a ski area makes accessing the areas out of bounds easy, but with no avalanche hazard reduction these easily accesible areas can be deadly. Come learn what it takes to stay safe. Open to skiers and snowboarders.

February Forecaster Round Table | 02/03/2016 |

Join the Payette Avalanche Center Forecasters each Wednesday in February to discuss a different avalanche topic ( weather and snowpack, terrain and route finding, human factors, and rescue fundamentals).

February 13 Friends of the Payette Avalanche Center Fundraiser at Little Ski Hill-drinks, bbq, silent acution and night skiing! This yearly family friendly event is not to be missed!

Also, Home Town Sports has a lot of fun on tap: Registration is now open for the Hometown Race Series and Après Ski Party on Saturday January 30th at Brundage and Bear Basin! check out their webpage http://mccallwintersportsclub.org/support/apres-ski-party/

recent observations

This past week has been an active one for natural and human caused avalanches. While there have been no new reports of natural avalanches in the last few days, professionals are still reporting human triggered avalanches in isolated north facing terrain. These human triggered slides are failing on buried surface hoar that now is buried under 2+ feet of snow. As for the new snow that has fallen over the weekend, it was readily available for wind transport. Sunday, we were able to trigger small wind slabs on east northeast slopes and they averaged about 6 inches deep. Expect to see deeper wind slabs in higher exposed terrain. 

Yesterday, we toured the Rapid drainage, East of Jug Mouuntain, and did not see any natural activity. 

weather

Mostly sunny today with warmer temps than yesterday, around 33 degrees in the mountains. Light winds out of the west will be in the 7 MPH range. Thursday, a zonal flow (west to east) will bring precipitation into the advisory area through the weekend, until then, we will see a trend towards warming, with slightly inverted temps and slight chances of snow.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: Patchy fog before 11am. Otherwise, mostly sunny, with a high near 29. Calm wind. Mostly cloudy, with a low around 19. Calm wind. A 10 percent chance of snow showers before 11am. Cloudy, with a high near 33. Calm wind.
Temperatures: High 29 deg. F. Low 19 deg. F. High 33 deg. F.
Wind direction:
Wind speed: Calm Calm Calm
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Mostly sunny, with a high near 33. West wind around 7 mph. A 20 percent chance of snow showers after 11pm. Mostly cloudy, with a low around 23. West southwest wind around 7 mph. A 20 percent chance of snow showers before 11am. Cloudy, with a high near 35. Southwest wind 7 to 10 mph.
Temperatures: High 33 deg. F. Low 23 deg. F. High 35 deg. F.
Wind direction: West West Southwest South southwest
Wind speed: 7 7 7-10
Expected snowfall: 0 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 and describes general avalanche conditions, 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.