THIS AVALANCHE ADVISORY EXPIRED ON February 15, 2019 @ 6:10 am
Avalanche Advisory published on February 14, 2019 @ 6:10 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Hazard is High today.  Heavy snowfall combined with multiple days of strong winds have created dangerous wind slabs on upper elevation, exposed slopes.  Sluffing and storm slabs are also likely on slopes over 30 degrees. Warming temperatures and the possibility of rain on snow  this afternoon will add to the problem. Natural and Human caused avalanches are likely today.    

How to read the advisory


  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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The amount of new snow and wind effect that we have received  in the last few days has created dangerous conditions on many upper elevation slopes.  Wind slabs are growing, sliding, and re-forming daily. Natural wind slab avalanches have been observed over the last few days.  Some of these slabs are easy to feel or see but some are also getting covered up with the new and wind blown snow and will be difficult to recognize. Shooting cracks or hollow, sculpted snow are warning signs of wind slabs. Travel in wind loaded avalanche terrain is not recommended. Check out this short video of brittle wind slabs on a SW aspect from Tuesday.  Tamarack Ski Patrol also reported large avalanche activity that occurred both naturally and during avalanche mitigation operations yesterday. The possibility of rain combined with warming temperatures today may be enough to trigger another round of natural activity on slopes that have not avalanched yet.  Cornice failures are a concern today as well. give warming cornices and slopes below them a wide berth today.

 

Avalanche Problem 2: Storm Slab
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The amount of snow that has hit the West Central Mountains has been a big load really fast and pretty atypical for such a short time frame.  Temperature fluctuations and high winds have created slabs of various hardnesses across multiple slopes. Crusts, multiple graupple  layers and other weak layers exist within the snowpack and are buried 2-3 feet deep.  A warming trend with the possibility of rain in the lower elevations will add to the problem with warm snow falling on colder snow below.  Travel on steep slopes in the backcountry is not recommended at this time.  Wait for the snow and storms to calm down and allow the snowpack to adjust to the rapid loading. More snow today and through tonight will add to the problem.  Rain and warming temperatures this afternoon will increase the hazard on all slopes, especially lower elevation slopes.

Avalanche Problem 3: Loose Dry
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 Tuesday we were able to trigger D1+ sluffs on slopes with small cornice bombs. We also saw significant sluff piles at the bottom of the steep terrain near Clow Point.  If you are skiing or riding slopes approaching 35 degrees you will have sluffs moving with you. Some of these may be big enough to knock you off your skis or sled and push you into trees, off rocks or into other hazards.  Be aware of terrain traps that could allow sluffs to pile up deep. Rain or warming temperatures today may increase the possibility of natural wet or dry loose snow avalanches.

advisory discussion

PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.

Please be aware that there are areas that are CLOSED to motorized traffic in the McCall, Goose Lake and greater West Mountains area.  Just because there are tracks in some areas, does not mean they are open.  Please respect all users and closures.  See the Payette Winter Travel Maps for clarification.  Both the East and West maps can be downloaded on the Avenza app on your phone or are available at trailheads and local shops.   IT IS YOUR RESPONSIBILITY TO KNOW WHERE YOU ARE AND WHERE THESE CLOSURES EXIST. 

recent observations

We had a fairly clear day Tuesday in between storms and were able to see Natural Avalanches on several upper elevation, wind loaded slopes.  In addition, slopes over 35 degrees were sluffing naturally and shedding some of the new snow.   Our 600's were challenged on all but the flattest terrain and we found challenging skiing conditions on Southerly, wind exposed slopes where stiff, wind slabs were cracking under the weight of our skis and failing on isolation in our pits(see video)  Deep snow is keeping sleds off steep slopes for now and avoiding the steeps for the next few days is the best thing you could do right now.  

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 23 deg. F.
Max. temperature in the last 24 hours: 23 deg. F.
Average wind direction during the last 24 hours: WSW
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: 23 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

.SHORT TERM...Today through Saturday...Warm front oriented
east-west across our southern zones this morning will shift
north during the day. Behind the warm front is a sharp rise
in snow levels. By this afternoon snow levels will range
from 6000 feet in northern zones to 7000 feet in the south.
The warm front will also bring a lot more pcpn, either as
rain or as snow changing to rain. Water content will average
around a full inch in the Boise Mountains where heavy rain
and high-mountain snow will continue. The recent heavy snow
in the mountains should absorb much of the rain. Elsewhere,
water content will average 1/3 to 2/3 of an inch with largest
amounts in Malheur County, the Lower Treasure valley, and
Weiser River Valley. Pcpn will decrease from south to north
later today and this evening.

Next will come the cold front, expected in eastern Oregon tonight
and western Idaho Friday morning. The front will bring more
showers followed by rapidly lowering snow levels, and several
inches new snow in the mountains. The front will also bring
gusty winds as it passes. Showers of snow, or rain changing
to snow, will continue through Saturday as the main upper
trough passes through the area.

Temps will be mild today and tonight, then cooling Friday
through Saturday.

.LONG TERM...Saturday night through Thursday...A long wave
trough will persist over the region through Sunday with snow
showers in higher terrain and temperatures well below normal.
Northerly flow will provide a break in unsettled conditions
before the next system approaches from the north on Wednesday,
spreading light snow showers across the region into Thursday.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Thursday Thursday Night Friday
Weather: Rain and snow. High near 36. Calm wind. Chance of precipitation is 100%. Total daytime snow accumulation of less than one inch possible. Rain showers before 11pm, then snow showers likely. Low around 27. Light and variable wind becoming south southwest 5 to 10 mph after midnight. Chance of precipitation is 100%. New snow accumulation of around an inch possible. Snow showers likely. Cloudy, with a high near 31. South southwest wind 6 to 10 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 36 deg. F. 27 deg. F. 31 deg. F.
Wind direction: Calm SSW SSW
Wind speed: Calm 5-10 6-10
Expected snowfall: Trace in. 1 in. 1-2 in.
Granite Mountain at 7700 feet.
  Thursday Thursday Night Friday
Weather: Snow. High near 30. South southeast wind around 7 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 3 to 5 inches possible. Snow showers. Low around 17. South southwest wind 7 to 13 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 7 inches possible. Snow showers. High near 19. South southwest wind 8 to 11 mph. Chance of precipitation is 80%. New snow accumulation of 3 to 7 inches possible.
Temperatures: 30 deg. F. 17 deg. F. 19 deg. F.
Wind direction: SSE SSW SSW
Wind speed: 7 7-13 8-11
Expected snowfall: 3-5 in. 3-7 in. 3-7 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.