THIS AVALANCHE ADVISORY EXPIRED ON February 25, 2017 @ 6:43 am
Avalanche Advisory published on February 24, 2017 @ 6:43 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger is Considerable above 7000 feet today on wind affected slopes. Winds gusting around the compass over the last 5 days have left multiple layers of wind slabs sensitive to the weight of a skier or snowmobiler scattered across exposed, upper elevation terrain. The Avalanche Danger in wind protected areas where soft snow exists and below 7000 feet is Moderate.  In the lower elevations, expect Low danger where the snowpack is well consolidated.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
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  • Size ?
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The good news is that most of our avalanche problems are confined to upper elevation and wind exposed slopes right now.  The bad news is that after a week of moderate to high winds that have swirled around the compass, wind slabs are widespread on multiple upper elevation aspects.  Wednesday, the older wind slabs that were mostly found on our northerly terrain were showing signs of stabilizing until North winds ramped up Wednesday afternoon and evening. By yesterday afternoon, wind loading on Southerly slopes had built up very sensitive, shallow(less than 1 foot) wind slabs that were easily triggerable by ski cutting.  North, Northeast and Northwest winds continued through the night last night with gusts into the 20 mph range adding to the depth of the newest crop of wind slabs.  

Older generations of wind slabs can be found on multiple aspects as well.  Stability tests by local snow professionals over the last 2 days have produced mixed results across the forecast area with moderate to hard CT scores failing in multiple layers above the February 9 raincrust now buried near 100 cm or about 39 inches down.  The more shallow layers(between 10 and 20 inches) are easier to trigger and have the potential to overload layers below or step down into layers almost as deep as the raincrust over 3 feet down.

Northerly slopes quickly lost their soft snow yesterday and were transforming into consistencies ranging from firm but punchy to stout styrofoam throughout the day yesterday.  Soft snow conditions exist on protected slopes where stability and skiing or riding is much better. Ridgetops have been scoured to the rain crust in many areas creating a glazed surface that is almost impossible to edge in on skis and almost impervious to the skegs of a snowmobile.

advisory discussion

Snowmobiler/Snowbiker Travel Restrictions: Please respect these closures and other users recreating in them.  Winter Travel Map(East side). You can download the map to the AVENZA app on your phone, and know your exact location while you are out riding.  It is your responsiblity to know where closures exist on the forest.

The Granite Mountain Area Closure is in effect Jan15-March 15, please respect Snowcats operating in this and nearby areas.  In addition there are other areas on the Payette National Forest that are CLOSED to snowmobile traffic including Jughandle Mt east of Jug Meadows,North of Boulder Mtn, East of Rapid Peak,  Lick Creek/Lake Fork Drainage (on the right side of the road as you are traveling up canyon), and the area north of Brundage Mt Ski area to junction "V" and along the east side of Brundage and Sergeants' Mts. with the exception of the Lookout Rd( junction "S").

 The Friends of the Payette Avalanche Center (FPAC) needs YOU! We are in desperate need of more user support and financial assistance. The avalanche forecast is not a guaranteed service, and is in jeopardy of dwindling down to only a couple of days a week in the near future. Please help if you can by clicking the DONATE tab above. If you value this life saving information, make a donation or help the FPAC in raising funds for the future.

recent observations

Several Northerly slopes failed earlier this week producing large avalanches almost down to the rain crust.  Skiers and Snowmobilers were able to trigger shallow wind slabs and storm slabs in many places as well. While these slabs have begun to stabilize over the week, avoiding steep wind affected terrain is going to be your most prudent choice today.  Small sluffs or loose, dry avalanches were also a concern on steep slopes.  A good practice and route finding excercise is to consider the consequences of something breaking before you get out on steeper terrain. What kind of slope is it?  Where would an avalanche take you? Are there trees or rocks below? Is there an escape route available? 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 4 deg. F.
Max. temperature in the last 24 hours: 13 deg. F.
Average wind direction during the last 24 hours: N
Average wind speed during the last 24 hours: 9 mph
Maximum wind gust in the last 24 hours: 30 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: 76 inches
weather

SHORT TERM...Today through Saturday...Snow shower activity will dissipate across the Snake Plain and southwest Idaho mountains this morning as remnants of yesterday`s storm pulls east. Any additional accumulations in the Western Magic Valley are less than an inch, with 1-2 inches in the central Idaho mountains. Drier air to the west clears out cloud cover across southeast Oregon and far southwest Idaho today, though a cold air mass remains in place. Though some cloud cover lingers, tonight is cold, with single digit lows in southeast Oregon and below zero temperatures in the colder mountain valleys of southwest Idaho. Saturday brings an increase in clouds and a chance of snow to areas along the NV border and central Idaho mountains as an upper trough drops through the Pac NW. Temperatures remain cold through Saturday, averaging 10-15 degrees below normal

LONG TERM...Saturday night through Thursday...Model agreement is above average. An upper level trough from Alaska will deepen as it moves into the longwave trough over the Intermountain Region on Sunday. This will bring more snow and continued cold temperatures through Monday. Snowfall in the valleys is expected to be light. The mountains will see heavier accumulations, especially over central Idaho and Baker County Oregon. This will be the last system from the north, as an upper level ridge approaches the west coast, and the flow over our area shifts to northwesterly. There will still be a chance of snow showers Monday night and Tuesday, followed by dry weather Tuesday night through Thursday. Temperatures will slowly moderate, but will still average 5 to 10 degrees below normal.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Scattered snow showers, mainly before 11am. Cloudy, with a high near 25. Northwest wind 5 to 7 mph becoming calm in the morning. Chance of precipitation is 30%. New snow accumulation of less than a half inch possible. Mostly cloudy, with a low around 1. West wind around 5 mph becoming calm in the evening. A 20 percent chance of snow showers after 11am. Mostly cloudy, with a high near 24. Calm wind becoming southwest around 6 mph in the afternoon.
Temperatures: 25 deg. F. 1 deg. F. 24 deg. F.
Wind direction: NW W SW
Wind speed: 5-7 Around 5 Around 6
Expected snowfall: Trace in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Scattered snow showers, mainly before 11am. Cloudy, with a high near 18. Wind chill values between -6 and 4. North wind 9 to 14 mph becoming light and variable in the morning. Chance of precipitation is 30%. New snow accumulation of less than a half inch possible. Mostly cloudy, with a low around 4. Wind chill values between -2 and -7. West wind around 5 mph becoming calm. A 30 percent chance of snow showers after 11am. Mostly cloudy, with a high near 20. Wind chill values between -7 and 3. West southwest wind around 7 mph. New snow accumulation of less than a half inch possible.
Temperatures: 18 deg. F. 4 deg. F. 20 deg. F.
Wind direction: N W SW
Wind speed: 9-14 Around 5 then calm Around 7
Expected snowfall: Trace in. 0 in. Trace 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.