THIS AVALANCHE ADVISORY EXPIRED ON February 17, 2018 @ 7:02 am
Avalanche Advisory published on February 16, 2018 @ 7:02 am
Issued by Jess Asmussen - Payette Avalanche Center
bottom line

A moderate avalanche hazard exists after 6-10 inches of cold, low-density snow fell above a solid melt/freeze layer. Loose dry snow avalanches that are large enough to injure a person are possible on all aspects where the terrain is greater than 35 degrees. At the upper elevations, winds have transported the new snow and formed fresh wind slabs. New snow and moderate winds throughout the day will continue to build an additional load.  

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Dry
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Loose dry snow avalanches are possible in steep terrain on all aspects at the middle and upper elevations. This light and fluffy new snow sits on top of a very firm, supportable layer (see video). While these avalanches are not likely to be large enough to bury a person, they could push you into trees, rocks, or terrain traps where a burial is possible.

Skiers and riders who commit to steep terrain should do so one at a time and avoid terrain that ends in terrain traps. Terrain traps are slopes that terminate in features such as gullies, trees, abrupt transitions, or cliff bands. 

Avalanche Problem 2: Wind Slab
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Fresh wind slabs are possible at the upper elevations and on exposed terrain features. The 24-hour average wind speeds from remote weather stations were in the teens, yet high enough to move and transport snow. The likelihood of triggering these slabs will increase throughout the day as the next storm arrives bringing snow and increasing winds. 

advisory discussion

SHORT TERM...Today through Saturday...Northwest flow will bring
increasing moisture across the north today. Light snow will
develop in the higher terrain of Baker County and in the West
Central Mountains of Idaho where accumulations of 1 to 3 inches
are expected. The snow will continue in these same areas tonight
for additional light accumulations. The remainder of southeast
Oregon and southwest Idaho will be dry with partly to mostly
cloudy skies. A low pressure system will move into the Pacific
Northwest on Saturday. Winds will increase across the area as the
system approaches - becoming breezy by afternoon. Snow will
continue in the northern mountains and will intensify with several
inches of accumulation expected, mainly above 5500 feet. Snow
levels will rise through the afternoon, to around 4000 feet in the
north and 5500 feet in the south. There is a chance of
precipitation in the Treasure and Western Magic Valleys, with a
rain/snow mix (no accumulation) in the morning changing to rain
in the afternoon. Temperatures will be warmer (near normal) today
and above normal on Saturday.

.LONG TERM...Saturday night through Friday...A broadening trough
will continue to approach the area on Sunday bringing a continued
threat of precipitation on Sunday. Snow levels will rapidly drop
to valley floors on Sunday. The upper level axis finally sweeps
through on Monday, again, with precipitation continuing, then
rapid clearing late Monday into early Tuesday morning. By Tuesday,
the area is expected to be under a direct northerly flow which
will keep temperatures well below normal for a few days.
Conditions remain dry through Wednesday before a more moderate
northwest flow will increase temperatures to near normal, and
bring shortwaves through.

recent observations

Yesterday we toured in the Lick Creek area. We found 10 inches of low-density snow sitting on top of a hard layer that formed during the most recent warm weather (see video). We witnessed numerous small, natural, dry loose snow avalanches in steep terrain. The new dry snow was easy to trigger with ski cuts. Below the surface, several melt/freeze layers exist in the upper snowpack but snow stability tests indicated that these layers were fairly strong.

Prior to the recent storm, a very firm, supportable snow surface existed throughout the forecast area. The new storm came in cold and did not bond well to the old snow surface. Even with 10 inches of new snow, this layer is very noticable on skis or on a snowmobile. 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 11 deg. F.
Max. temperature in the last 24 hours: 19 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: 7 mph
Maximum wind gust in the last 24 hours: 16 mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: 68 inches
Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Snow likely. Cloudy, with a high near 30. South southwest wind 3 to 8 mph. Chance of precipitation is 70%. Total daytime snow accumulation of 1 to 2 inches possible. Snow likely, mainly before 11pm. Mostly cloudy, with a low around 22. South wind 3 to 7 mph. Chance of precipitation is 70%. New snow accumulation of around an inch possible. Snow. High near 34. South wind 5 to 14 mph. Chance of precipitation is 100%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 30 deg. F. 22 deg. F. 34 deg. F.
Wind direction: South South
Wind speed: Calm 3 to 7 mph 5 to 14
Expected snowfall: 1 to 2 in. 1 in. 2 to 4 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Snow likely. Cloudy, with a high near 25. Southwest wind 10 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 60%. Total daytime snow accumulation of 1 to 2 inches possible. Snow likely, mainly before 11pm. Mostly cloudy, with a low around 21. West southwest wind 11 to 17 mph becoming south after midnight. Winds could gust as high as 25 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. Snow. High near 30. Windy, with a south wind 20 to 30 mph, with gusts as high as 41 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 7 inches possible.
Temperatures: 25 deg. F. 21 deg. F. 30 deg. F.
Wind direction: Southwest West southwest South
Wind speed: 10 to 18 mph 11 to 17 mph 20 to 30 mph
Expected snowfall: 1 to 2 in. 1 to 3 in. 3 to 7 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.