THIS AVALANCHE ADVISORY EXPIRED ON February 6, 2017 @ 7:11 am
Avalanche Advisory published on February 5, 2017 @ 7:11 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger is HIGH above 6000 feet.  High winds, heavy snowfall, rain and the potential for rain above 6000 feet combined with above freezing temperatures are creating dangerous avalanche conditions.  Above 7000 feet, dense wind and storm slabs have been building over the last 48 hours.  Below 6000 feet the Avalanche Danger is CONSIDERABLE, wet loose avalanches are likely on steep slopes.  Today is a good day to avoid being on or under terrain steeper than 30 degrees.

How to read the advisory


  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Yesterday new wind slabs continued to build throughout the day with wind speeds in the upper 20 to 30 MPH range in the Northern Mountains and higher still along the West Mountain Crest. Winds were generally out of the S/SW but  W and NW winds were recorded in the afternoon. Rapid loading was occurring on leeward slopes and the lee side of even small terrain features around the compass.  These slabs are resting on a variety of old snow surfaces: sun and heat crusts, old wind slabs, wind board, light density snow, and in the northerly terrain weaker faceted snow(the persistent weak layers we have been tracking).  Avalanche size and likelihood will vary quite a bit because of these layers and the slabs resting on top of them. Cracking was widespread in wind affected terrain yesterday and Friday, additional snow and increasing wind velocities through the next few days will add to the likelihood of  both natural and human triggered avalanches. These avalanches have the potential to step down into older wind slabs or deeper buried weak layers creating the potential for large avalanches.  Cornices are also growing large and are very sensitive right now, avoid travel on or under cornices as the possibility of cornice collapses will be high today as well. 

Shallow, dense and sensitive wind slab on skin track from Friday afternoon.

Avalanche Problem 2: Storm Slab
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Warm snow over cold snow is piling up right now, storm totals are in the 6-16 inch range.  Because of the temperatures Snow Water Equivalent(SWE) is a more useful indicator of the stress being applied to the snowpack right now.  Local Snotel sites are reporting between 1.1 and 1.3 inches of SWE over the last 24 hours combined with similar totals from the previous period which is a fairly large load applied in a relatively short amount of time.  Additional snowfall is forecasted to continue throughout the day today with snow totals varying quite a bit according to elevation.  Slopes over about 30 degrees that don't slide on their own will be primed for a human trigger today.  Stick to lower angle terrain and pay attention to slopes above and around you. If released, there is a possibility that they could step down into weak layers buried deeper in the snowpack.  Winter Storm Warning is in effect through this afternoon and an Avalanche Warning is in effect through  Monday morning.

Shallow slab of dense snow resting above a weaker layer of the older and colder snow below at 7000 ft. near Goose Lake.

Avalanche Problem 3: Loose Wet
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Rain and  a mix of snow and rain is likely at elevations above 6000 feet today and tomorrow.  Rain on snow can quickly reduce the stability of the snowpack as it adds weight and breaks down the bonds within the snowpack.  Small, wet loose avalanches were widespread yesterday in the lower elevations and will be again today as mixed precipitation and warm temperatures produce stress the snowpack further.  These small avalanches don't move fast but can quickly entrain a large amount of material as they spread out and gain momentum on steep slopes.  These avalanches will likely be found near local roads, in river canyons and in areas we don't normally worry about avalanches.

advisory discussion

Snowmobiler/Snowbiker Travel Restrictions:  a quick reminder that the Granite Mountain Area Closure is now in effect, 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, 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").  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.

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

Reports of Avalanches throughout the area are just starting to come in.  

Yesterday there was a slide near Clow Point reported and cleared by the Brundage Catski operation that was big enough to block the snowmobile road.  Reports from the Boise Mountains described R2D2(see scale below) avalanches running on buried surface hoar on N,E and W aspects with crown depths between 16 and 24 inches.

The new dense snow was not bonding to the drier snow below, cracking of the cakey surface layer was observed in the mountains near McCall with ski cuts producing 8-12 inch breaks or crowns that lacked the energy for widespread propagation. Tamarack Ski Patrol reported large and sensitive cornice development with high South and Southwest winds near the summit through most of the day that produced significant loading on Northerly slopes and terrain features.

If you see or trigger avalanches today or over the next few days, please take a picture, let us know the direction the slope faced, approximate elevation and any information about the size of the avalanche.  You can post ANY observations on our site in just a few minutes and it helps the PAC forecasters get a better picture of what is happening across the advisory area.  You can also send a quick email with any information to our email at:  forecast@payetteavalanche.org 

Here is a handy reference tool for reporting avalanche size:

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 24 deg. F.
Max. temperature in the last 24 hours: 26 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: 9 mph
Maximum wind gust in the last 24 hours: 33 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

SHORT TERM...Today through Tuesday...Light snow continues across the central mountains of Idaho, with light rain showers being reported elsewhere. Radar returns continue to weaken, but light showers should continue through the night. The Winter Storm Warning for the central mountains will continue with another 2 to 5 inches possible through the afternoon hours.  Low pressure off Vancouver Island will send a cold front and associated moisture across the area on Monday which will move south through the area through Monday night. As this system progresses, snowfall coverage will increase with cooling temperatures. A slight chance of thunder was carried over from the previous forecast package, with the addition of activity added into the western Magic Valley as the front looks to move through the area late Monday afternoon. Tuesday will see a shift in weather patterns with the cold front leaving colder temperatures in its wake. The low pressure system causing the cold front will move over southern Canada and dissipate, but pacific moisture will keep some shower activity across the area. Snow levels will return to the valley floors for most of the area, with the Treasure Valley seeing some potential for a rain-snow mix in the afternoon.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: Rain and Snow Rain and Snow Rain and Snow
Temperatures: 36 deg. F. 33 deg. F. 36 deg. F.
Wind direction: South South South/ Southwest
Wind speed: 11 to 16 11 to 16 Around 16
Expected snowfall: 1-2 in. less than 1/2 in. less than 1/2 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: Snow Snow Snow before 11am then snow showers. Some thunder is also possible. Temperature falling to around 20 by 5pm.
Temperatures: 28 deg. F. 26 deg. F. 29 deg. F.
Wind direction: SSW SSW SW
Wind speed: 29 to 36 mph, with gusts as high as 48 32 to 38 mph, with gusts as high as 50 mph 32 to 40 mph, with gusts as high as 55 mph
Expected snowfall: 3-5 in. 2-4 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.