Avalanche Advisory published on February 25, 2017 @ 7:11:
This advisory is valid for 24 hours
Issued by Dave Bingaman -
bottom line

How to read the advisory

The Avalanche Danger is MODERATE 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 below 7000ft where soft snow exists is LOW.  Very firm snow and crusts will be found in the lower elevations.


Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.
weather

SHORT TERM...Today through Sunday...Fast moving trough dropping through the Pac NW this morning continues southward today. The main dynamics with this system are well offshore, which will its impact to isolated snow showers across far southeast Oregon and the west-central mountains in Idaho for today. Otherwise will see partly cloudy and cold conditions across the area. Weak warm advection keeps slight chance of showers in the central ID mountains overnight. This is ahead of a second cold upper level trough tracking from the Gulf of Alaska into the Pac NW for Sunday. Showers increase in coverage Sunday afternoon with increased instability ahead of the low center. Snow will fall to valley floors but accumulations will be limited to elevations above 4k feet MSL. Winds will also increase on Sunday with breezy conditions developing by afternoon. Temperatures are around 10 degrees below normal through Sunday

LONG TERM...Sunday night through Friday...The cold upper level trough will exit the Intermountain Region on Tuesday, leaving our area under northwest flow aloft. Temperatures will be around 10 degrees below normal Monday and Tuesday, but slowly moderate to around 5 degrees below normal on Friday as the upper level flow shifts to more westerly. Snow showers will be widespread Sunday night and Monday, then decrease to scattered Monday night and Tuesday. Precipitation will be mainly confined to the mountains of central Idaho and Baker County Oregon Tuesday night through Friday.

recent observations

Several Northerly slopes failed earlier this week producing large avalanches almost down to a weak layer near the Feburary 9th 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 are 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? Play it safe in wind affected terrain and enjoy all of the soft deep snow on protected aspects.  Sledders and skiers will find plenty of fresh snow out there right now.

Avalanche Problem #1: Wind Slab

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 Wednesday afternoon, wind loading  near the ridgetops 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 yesterday AM 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 week have produced mixed results across the forecast area with moderate to hard CT scores failing in multiple layers above the February 9 rain crust now buried between 80 and 100 cm or about 3- 3.5 feet 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.(see photo)

Northerly slopes quickly lost their soft snow Thursday and were transforming into consistencies ranging from firm but punchy to stout, scoured, styrofoam on Thursday.  Great 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, North of the 20 mile drainage, 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.We have equipment that is overdue for replacement but lack the funds to purchase new gear including weather station parts and our forecast sleds.  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.

CURRENT CONDITIONS  Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 4 deg. F.
Max. temperature in the last 24 hours: 16 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: 5 mph
Maximum wind gust in the last 24 hours: 25 mph
New snowfall in the last 24 hours: inches
Total snow depth: 79 inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000-8000 ft.
  Saturday Saturday Night Sunday
Weather: Isolated snow showers after 11am. Cloudy, with a high near 24. Calm wind becoming southwest 5 to 7 mph in the afternoon. Chance of precipitation is 20%. A 30 percent chance of snow showers, mainly after 11pm. Cloudy, with a low around 11. Southwest wind 5 to 7 mph becoming calm. New snow accumulation of less than one inch possible. Snow showers likely, mainly after 11am. Cloudy, with a high near 26. South southeast wind 6 to 10 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 24 deg. F. 11 deg. F. 26 deg. F.
Wind direction: Calm SW SSE
Wind speed: Calm 5-7 6-10
Expected snowfall: 0 in. 1 in. 1-3 in.
For 8000-9000 ft.
  Saturday Saturday Night Sunday
Weather: Isolated snow showers after 11am. Cloudy, with a high near 18. Wind chill values between -8 and 2. Southwest wind 5 to 8 mph. Chance of precipitation is 20%. A 30 percent chance of snow showers, mainly after 11pm. Cloudy, with a low around 11. Wind chill values between -3 and 6. Southwest wind 7 to 11 mph. New snow accumulation of around an inch possible Snow showers, mainly after 11am. High near 21. Breezy, with a south wind 15 to 21 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 18 deg. F. 11 deg. F. 21 deg. F.
Wind direction: SW SW S
Wind speed: 5-8 7-11 15-21
Expected snowfall: 0 in. 1 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.