THIS AVALANCHE ADVISORY EXPIRED ON December 11, 2016 @ 7:18 am
Avalanche Advisory published on December 10, 2016 @ 7:18 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

NO RATING is given for the West Central Mountains due to limited observations prior to the current storm.  Based on the new snow and rising temperatures, you should be wary of the bond between the new snow and the old, light density snow if you are approaching avalanche terrain over the next few days. We will begin issuing danger ratings next week. Please let us know what you are seeing if you are out in the mountains.

How to read the advisory

Avalanche Problem 1: Storm Slab
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If you are traveling in or near avalanche terrain today be aware of what the new snow is doing and what it is resting on. Conditions prior to the storm were perfect for the formation of persistent weak layers in the existing snow pack.  Watch for obvious signs of instability like cracking or collapsing of the snow pack. With 12+ inches of new, warmer snow on the older, unconsolidated snow below it is likely that you will encounter shallow Storm Slab instabilities in the new snow and possible that these slabs may go deeper into the older snow below.  Be aware too that the new snow will be doing a great job of camouflaging buried rocks, downfall and stumps that were visible a few days ago.

Avalanche Problem 2: Wind Slab
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Winds accompanying the current storm have been relatively light overall but during the last 24 hours gusts out of the S and SW may have transported enough snow for the formation of thin windslabs on leeward, upper elevation slopes. Wind speeds in the high teens and low 20's were recorded at Secesh Snotel, Brundage and Tamarack Resorts. 

recent observations

PAC has not begun collecting regular observations yet this season but we did get out on Tuesday and Wednesday to check out the snow coverage prior to the storm. We found a thin and unconsolidated snow pack varying between 22 and 30 inches in depth. Travel off trail was sketchy at best and given the amount of buried treasure lurking under the snow downright hazardous.  The warmer snow will help consolidate  the cold, light density snow and hopefully set us up with a decent base so travel will be improving.  

 

Quick pit on East Aspect of Brundage Mt. from 1/6/16 showing thin, unconsolidated snow pack with some faceted snow near the ground.

View from Hard Creek area looking S. towards Granite MT.  Thin coverage off trail 1/7/16

 

weather

The cold weather ended abruptly yesterday with valley temperatures rising through the day to near freezing overnight.  Periods of moderate to heavy snowfall have left us with about a foot of new snow at 6400 ft. over the last 48 hours. Winds have been light with gusts reaching near 20 mph out of the SW.  Additional snowfall of  2-4 inches is expected through the day today with another 12-16 inches forecasted through Monday afternoon. Areas to the South and East of McCall will likely see additional snowfall and have already collected more snow than the mountains near McCall.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: now before 11am, then a chance of snow showers after 11am 40 percent chance of snow showers, mainly after 11pm Snow likely, chance of precipitation is 60%
Temperatures: falling to 25 deg. F. 16 deg. F. 26 deg. F.
Wind direction: S then SW variable S
Wind speed: 5-7 Light 5-9
Expected snowfall: 1-2 in. 1 in. 1-3 in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow before 11am, then snow showers likely after 11am. A 50 percent chance of snow showers. Snow, chance of precipitation is 70%
Temperatures: 28 deg. F. 18 deg. F. 23 deg. F.
Wind direction: W/SW West southwest becoming light west northwest. S/SW
Wind speed: 13-16mph 6-11 13-17
Expected snowfall: 2-4 in. 1-3 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.