THIS AVALANCHE ADVISORY EXPIRED ON February 12, 2019 @ 6:58 am
Avalanche Advisory published on February 11, 2019 @ 6:58 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Hazard is High today.  Natural avalanches are likely and Human triggered avalanches are Very Likely. Over 2 feet of snow is forecasted and ridge tops will see gusts upwards of 30 MPH over the next couple days that will continue to create wind slabs.  It is also possible to trigger soft storm slabs in the upper 2 feet. Cornices are growing, and will likely fail.  Travel in, or near avalanche terrain is not recommended 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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Winter storm warnings are all over the weather feeds. The amount of new snow and 30 MPH wind gusts forecasted over the next few days is raising red flags. Wind slabs are growing, sliding, and re-forming daily. Natural wind slab avalanches have been observed over the last few days.  Travel in wind loaded avalanche terrain is not recommended.

 

 

 

Avalanche Problem 2: Storm Slab
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Be aware that a lot of new snow has fallen on a fresh crop of Surface Hoar and Near Surface Faceted snow ( recycled powder) on quite a few slopes. 

As the new snow accumulates over the next few days put your free for all goggles back in the bag and bust out the avalanche goggles to keep you safe. Practice safe riding and skiing, check your beacon batteries and keep your eyes on your partners. Pay attention to the slope angle and stay away from terrain over 30 degrees.

Avalanche Problem 3: Loose Dry
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While we are not recommending travel in avalanche terrain right now, if you did get on a steep slope, you should expect the new snow to run with you.  As we add more light density snow on what is already there, sluffing will increase in size and its ability to travel.

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

Yesterday, we toured the Pearl Lake area on the Crest line Trail above McCall. Opportunties for good photos were limited. The winter storm was in full effect with copious wind and new snow. The wind was gusting so hard at times that the visibility was non-existent. We observed some strong wind transport, and a couple of natural wind slab avalanches on leeward terrain that was getting a beat down with all of the wind scouring, sculpting and transport. Cornices were growing before our eyes. 

We were able to get a 1-2 foot wind slab to crack, break, and run with us on a small test slope with a cornice on our snowmobiles. The new snow was DEEP, and challenged us throughout the day. We were able to get some good loose sluffs  moving with us on steep slopes. Our test pits showed moderate results in the newer snow, and hard results with propagation on the older snow interface. Surface hoar was the weak layer in the shallower failures, and some near surface facets are still preserved enough to facilitate propagation with a hard load.

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 6 deg. F.
Max. temperature in the last 24 hours: 15 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 4 mph
Maximum wind gust in the last 24 hours: 20 mph
New snowfall in the last 24 hours: 8 inches
Total snow depth: 73 inches
weather

 

Area Forecast Discussion...CORRECTED
National Weather Service Boise ID
308 AM MST Mon Feb 11 2019

.SHORT TERM...Today through Wednesday...Snow continues to impact
the area this morning, with some snow being reported across the
Treasure Valley in addition to the mountains. Snowfall will
continue, and looks to impact portions of the Treasure Valley
through the morning commute before weakening across the valleys.
Heavier snowfall continues across the higher elevations through
Tuesday morning. A lull in overall snowfall (including the
mountains) is anticipated Tuesday afternoon as the area
transitions between two winter systems. Snowfall is expected to
return Tuesday night with the arrival of the next system.
Additional snowfall then continues into Wednesday, with heavy snow
in the mountains. Temperatures will warm through the next couple
of days, helping in the development of a rain-snow mix for
portions of the valleys on Wednesday. For the mountains, snowfall
will be heaviest across the central mountains of Idaho and into
Baker County, Oregon. Winter Storm Warnings and a few Winter
Weather Advisories remain across the most snow impacted areas
through Wednesday.

.LONG TERM...Wednesday night through Monday...An unsettled pattern
persists as several low pressure systems cycle across the region
through the extended. Snow showers continue to sweep across the
region into Thursday. As this system clears the region by Thursday
night, another wave of widespread snow showers approaches Friday and
lingers through the weekend. Monday is the first day in the extended
that may offer some relief from persistent snow showers.
Temperatures through the period will remain several degrees below
normal, and snow on the ground may cause temperatures to drop even
lower.

&&

.AVIATION...Mostly VFR with areas of MVFR/IFR in snow. Mountain
obscuration. Much of the showers will be confined north of a KBNO-
KJER line for higher elevations. Surface winds: southeast 5-15 kts
with gusts of 25-35 kts during the afternoon for areas south of the
Snake Plain. Winds aloft to 10k feet MSL: westerly 45-55 kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Snow. High near 25. South southwest wind 6 to 10 mph, with gusts as high as 21 mph. Chance of precipitation is 90%. Total daytime snow accumulation of 3 to 5 inches possible. Snow. Low around 20. South southwest wind 9 to 11 mph, with gusts as high as 23 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible Snow. High near 28. South wind 9 to 13 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 25 deg. F. 20 deg. F. 28 deg. F.
Wind direction: SSW SSW S
Wind speed: 6-10 9-11 9-13
Expected snowfall: 3-5 in. 2-4 in. 1-3 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Snow. High near 17. Wind chill values between -9 and 1. South southwest wind 8 to 16 mph, with gusts as high as 29 mph. Chance of precipitation is 90%. Total daytime snow accumulation of 8 to 12 inches possible. Snow. Low around 13. Wind chill values between -1 and 4. South southwest wind 11 to 18 mph, with gusts as high as 31 mph. Chance of precipitation is 90%. New snow accumulation of 7 to 11 inches possible. Snow. High near 18. Wind chill values between -2 and 3. Breezy, with a south wind 16 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 17 deg. F. 13 deg. F. 18 deg. F.
Wind direction: SSW SSW S
Wind speed: 8-16, Gusting 29MPH 11-18, Gusting 31MPH 16-20
Expected snowfall: 8-12 in. 7-11 in. 2-4 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.