THIS AVALANCHE ADVISORY EXPIRED ON January 25, 2016 @ 7:00 am
Avalanche Advisory published on January 24, 2016 @ 7:00 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger remains CONSIDERABLE on upper elevation terrain. Windslabs on steep, leeward slopes are widespread in the upper elevations.  A layer of Buried Surface Hoar has been responsible for several natural, and human triggered avalanches this week in both the upper and middle elevations.  Safe travel techniques, including sticking to lower angle slopes and keeping an eye on your partners are essential survival tools right now.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Wind slabs and wind loaded terrain continue to be a problem in the upper elevations. The mountains picked up another 4-6 inches in the last 24 hours wth some moderate SW winds.You are most likely to find these slabs at or near the ridgetops or on exposed terrain above 7000 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 earlier this week, so you may not see any visual clues. 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  weak, 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
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

While time may heal the fact that you missed all the fresh powder over the last week, it is not necessarily healing our snowpack right now. A layer of buried surface hoar that formed during the New Year's high pressure is continuing to produce large human caused avalanches. This layer has been slowly covered over the last 2 weeks and has failed in some areas, and is still waiting for a trigger in other places.  If you take 5 minutes to dig into the snow right now, you can see exactly where this layer is and what is on top of it. 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. These are photos showing 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) with impressive results on 28-30 degree slopes. The slab overlying this layer has become very firm this week with the warming temperatures and would be a nasty grinder if you were caught in the debris. 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.

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

     

Profile and photo of the crown  in the slide above done on 1/23/16 weak layer is visible as thin gray line near bottom of pit.

advisory discussion

Thanks to everyone that came out in the weather yesterday for our Sleducation class, great group, great class, perfect conditions!  Don't forget to check our Events page for details about our next class and upcoming fundraiser.

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... more

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... more

February 23 Friends of the Payette Avalanche Center Fundraiser at Little Ski Hill-drinks, bbq, silent acution and night skiing! Don't miss this one it's going to be a hoot!

recent observations

You will see plenty of old avalanche crowns scattered around if you are in the mountains today. Most of the partially covered,  natural release slides happened early last week, some are recent and have a light dusting of new snow covering them. While the hazard of natural avalanches has calmed down over the last few days, there have been several new human caused slides that were triggered over the last 3 days.  Ski cuts in northerly terrain by local ski guides continue to produce impressive slides in relatively protected terrain.  The layer responsible for these slides is the buried surface hoar that we have been finding in our pit tests over the last 2 weeks. We also saw a lower elevation slide that was triggered by a snowmobile playing on the roadcut on the Goose Lake Rd. near Clow Point. That smaller slide also failed on the layer of buried surface hoar.  We have noted that in the older slides that  the crowns were very wide or had propagated easily over a very long distance through complex terrain which is what happened on the ski cut triggered slide near Brundage Reservoir. This type of propagation over long distances is a trademark of a Buried Surface Hoar layer. This layer is well preserved in many places right now and the overlying slab is composed of 2+ feet of very firm snow. Where it did not release naturally, it is still waiting for a trigger.

 

NNW aspect skier triggered slide in a steep rollover from Saturday.  This was triggered by the 4th skier that skied the slope.

Sled triggered test slope on the Goose Lake Road near Clow Point triggered Friday.

weather

.SHORT TERM...TODAY THROUGH MONDAY...AN UPPER LEVEL TROUGH WILL DEPART TO THE EAST TODAY AND TAKE SNOW SHOWERS WITH IT AS NW FLOW ALOFT BECOMES ESTABLISHED. THESE SNOW SHOWERS WILL BE MOST NUMEROUS IN THE WEST-CENTRAL MOUNTAINS THIS MORNING. THERE IS STILL A CHANCE FOR AN EARLY-MORNING SNOW SHOWER IN THE TREASURE AND MAGIC VALLEYS...BUT THIS CHANCE WILL END BY 8 AM. EVEN AS AN UPPER LEVEL RIDGE BUILDS IN TODAY...A TROUGH EMBEDDED IN THE EAST SIDE OF THE RIDGE WILL SLIDE IN FROM THE NW LATE TODAY INTO TONIGHT. THIS TROUGH WILL SPREAD LIGHT PRECIPITATION INTO MAINLY HARNEY COUNTY. AS THE RIDGE BECOMES FIRMLY ESTABLISHED SUNDAY NIGHT...DRYING WILL OCCUR AND THERE WILL BE NO CHANCE OF PRECIP MONDAY. THE RIDGE WILL USHER IN AN INVERSION THAT WILL LAST INTO THE WEEK. FOG WILL FORM SUNDAY NIGHT IN THE USUAL MOUNTAIN- VALLEYS...ESPECIALLY THE LONG VALLEY...AND ALSO IN THE VALLEYS OF BAKER COUNTY AND IN THE LOWER TREASURE VALLEY. TEMPS WILL BE A FEW DEGREES ABOVE NORMAL TODAY...THEN NEAR NORMAL TONIGHT AND MONDAY. 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: Chance of precipitation is 60%. New snow accumulation of less than one inch possible. A 20 percent chance of snow showers before 11pm. Patchy fog after 11pm. Otherwise, mostly cloudy, with a low around 9. Calm wind. Patchy fog before 11am. Otherwise, mostly sunny, with a high near 28. Calm wind.
Temperatures: 33 deg. F. 9 deg. F. 28 deg. F.
Wind direction: West Calm Calm
Wind speed: Light Calm Calm
Expected snowfall: trace in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: Snow showers, mainly before 11am. High near 30. West northwest wind 7 to 9 mph. Chance of precipitation is 90%. Total daytime snow accumulation of around an inch possible. A 20 percent chance of snow showers before 11pm. Partly cloudy, with a low around 14. North northwest wind 5 to 7 mph. Mostly sunny, with a high near 29. West wind around 6 mph.
Temperatures: 30 deg. F. 14 deg. F. 29 deg. F.
Wind direction: W/NW N/NW West
Wind speed: 7-9 5-7 6
Expected snowfall: 1 in. 0 in. 0 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center with help from the Friends of the Payette Avalanche Center. This advisory covers the West Central Mountains in the Northern half of Valley County and the Eastern portion of Adams County. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general snow and avalanche conditions throughout the advisory area, local variations should be anticpated. 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.