THIS AVALANCHE ADVISORY EXPIRED ON January 20, 2016 @ 7:15 am
Avalanche Advisory published on January 19, 2016 @ 7:15 am
Issued by George Halcom - Payette Avalanche Center
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The Avalanche Danger remains Considerable on wind loaded, upper elevation slopes. Buried weak layers on protected aspects will make it possible to trigger avalanches in non wind affected terrain. Six inches of new snow Monday night, along with moderate winds out of the East, and South East have added fresh wind slabs on leeward slopes. Skiers reported triggering slabs on buried surface hoar, about a foot and a half deep now. Play it safe and stick to low angle terrain.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Wind slabs and wind loaded terrain remain the primary concern today.  Monday night, the mountains got another 6 inches of snow, and some moderate winds out of the East/ South East, creating fresh slabs on West through North slopes. Wind slabs are widespread in the upper elevations and range in sensitivity from easily triggerable to resistant. They also range in size from a few inches to a few feet in some areas. New snow over the last few days has also done a great job camouflaging some of the wind slabs formed earlier this week, so the tell tale signs may be covered. With plenty of light snow available for transport, Northerly terrain is suspect right now.  You may also find crossloaded areas on SE, E and W facing aspects where smaller terrain features have caught the blowing snow. Remember that wind slabs will often allow you to get further out on them than a storm slab before they fail.  Also, some of these wind slabs may be resting on a weak layer of faceted snow or surface hoar that was buried earlier in the week.  Your best bet is to avoid steep, wind loaded areas right now and through the next few days.

Avalanche Problem 2: Persistent Slab
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 Several different weak layers formed on or near the snow surface during the last period of high pressure and are lurking in our snowpack right now.  These persistent weak layers have slowly been buried this week and have failed (natural avalanche cycle mid week) in some areas, and are still waiting for a trigger in other places.  These layers include buried surface hoar and near surface faceted snow on shadier aspects and a series of unsupportable and supportable crusts on the Southerly aspects. If you take 5 minutes to dig into the snow right now, you can see exactly where these layers are, they are pretty obvious in the snowpack.

Yesterday,we got reports of skiers near Slab Bute and Granite Mountain triggering steep rollovers down to the buried surface hoar about a foot and a half deep now, one skier was pushed into a tree well, and buried up to his thighs. As we get more snowload on this weak layer, the likelyhood of triggering increases...we are watching this layer closely, and are finding it everywhere, especially areas that have been protected from the wind.

Surface Hoar and faceted snow are responsible for the majority of avalanche incidents and fatalities throughout the world. As we get additional snowfall combined with warming temperatures and strong winds, there is a good possibility that we will see another round of natural avalanches.  The risk of human caused avalanches will be rising today and tomorrow as well. The avalanche problem is increasing in both probability and size right now and requires an attitude and mindset adjustment from what we have been seeing over the last few weeks. Gone is the time for a go for it attitude, now is the time to travel safe and avoid steep terrain.

advisory discussion

The avalanche danger remains considerable, which is a common time for accidents...don't be complacent as we get more snow and wind re-setting out problems as well as coverage...this is the time to error on the side of caution.

recent observations

Yesterday, we toured up Lick Cr near 8302.We found a natural avalanche just below the ridgeline on the East face, from wind loading Monday Night that was medium sized, started in the new storm snow, and stepped down to our buried surface hoar layer...this slide was about a foot and a half deep, and large enough to bury or kill a person...we were able to trigger the rest of the slope easily with a cornice stomp from above, propigating around fingers, and creating an impressive powder cloud...R3 D2. We got reports from Payette powder guides of numerous natural avalanches on Beaverdam, and numerous other steep slopes on various aspects. Brundage Catski also reported similar small, natural avalanche evidence on steep west slopes. We were also able to ski trigger a SW aspect that was protected from the wind, down to the buriedd surface hoar.

The sun was out for a few hours while the clouds broke, and put some heat on Southern aspects, forming a one inch crust on the snow surface, rollerballs, and point releases near rocky outcrops.

weather

.SHORT TERM...TODAY THROUGH WEDNESDAY...INCREASING CLOUD DECK THIS
MORNING /AS OF 330 AM MST/ AS TODAY/S INCOMING PACIFIC SYSTEM
MOVES EAST INTO THE REGION. EXPECTING PRECIPITATION TO BEGIN IN
SOUTHEAST OREGON BY SUNRISE AND SPREAD INTO SOUTHWEST IDAHO THIS
AFTERNOON AND EVENING. THIS SYSTEM HAS A HEALTHIER MOISTURE PLUME
THAN PREVIOUS SYSTEMS AND LOOKS MORE DYNAMIC IN NATURE ON
SATELLITE. LARGEST PRECIP TOTALS WILL FALL IN SE OREGON THIS
AFTERNOON AND IN SW IDAHO THIS EVENING...WITH SNOW SHOWERS
CONTINUING IN THE WEST CENTRAL MOUNTAINS THROUGH WEDNESDAY
EVENING. LARGEST SNOW TOTALS WILL FALL IN THE HIGHEST ELEVATIONS
AND ROADS THROUGH MOUNTAIN PASSES COULD SEE A FEW INCHES OF
ACCUMULATION. TODAY/S MAXIMUM TEMPERATURE WILL BE A FEW DEGREES
COOLER THAN YESTERDAY/S WITH INCREASING CLOUD DECK AND
PRECIP...AND A FEW DEGREES COOLER STILL WEDNESDAY UNDER A
NORTHWEST FLOW.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow. High near 35. Calm wind becoming south southeast 5 to 8 mph in the afternoon. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible. Snow before 11pm, then snow showers after 11pm. Low around 25. South southwest wind 7 to 11 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible. Snow showers likely, mainly before 11am. Mostly cloudy, with a high near 32. South wind 3 to 5 mph. Chance of precipitation is 70%. New snow accumulation of less than one inch possible.
Temperatures: 35 deg. F. Low of 25 deg. F. 32 deg. F.
Wind direction: Calm-5-8 MPH S/SW S
Wind speed: Calm 7-11 MPH 3-5
Expected snowfall: 1-2 in. 1-3 in. less than one in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow. High near 32. Windy, with a south wind 17 to 22 mph increasing to 27 to 32 mph in the afternoon. Winds could gust as high as 46 mph. Chance of precipitation is 90%. Total daytime snow accumulation of 3 to 5 inches possible. Snow before 11pm, then snow showers after 11pm. Low around 21. Windy, with a west southwest wind 29 to 34 mph decreasing to 16 to 21 mph after midnight. Winds could gust as high as 49 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible Snow showers, mainly before 11am. High near 30. West wind 7 to 14 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 32 deg. F. Low of 21 deg. F. 30 deg. F.
Wind direction: S West/SW West
Wind speed: 27-32/ G 46 MPH 16-21/ G 49 MPH 7-14
Expected snowfall: 1 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.