THIS AVALANCHE ADVISORY EXPIRED ON March 12, 2019 @ 6:16 am
Avalanche Advisory published on March 11, 2019 @ 6:16 am
Issued by George Halcom - Payette Avalanche Center
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The Avalanche Hazard is Moderate today.  Human triggered soft slab, avalanches up to 1 1/2 feet deep are possible on steep slopes that have been protected from the wind and Sun, where buried surface hoar is supporting a soft slab, and might be waiting for a trigger. Buried weak layers exist in the top 2 feet of the snow pack including surface hoar and graupel.  Cornices are overhanging and should be avoided right now.

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Persistent Slab
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The mountains got another round of snow and wind Wednesday and while the storm was very wet in the lower elevations, above 7000 feet the snow and temperatures progressively cooled as a cold front pushed in early Thursday morning and left behind 10- 12 inches of new light density snow. The new snow fell on a variety of old snow surfaces including solar crusts, widespread Surface Hoar, and faceted snow that was growing on shaded slopes prior.  In addition, we have several layers of Graupel that are buried and where found are still a weak layer in the snow pack. 

 

 

 

Avalanche Problem 2: Wind Slab
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A fresh crop of wind slabs have formed on many upper elevation slopes.  Wind affected snow exists on some mid elevation slopes that were open and exposed to winds.  The winds which were mostly out of the SW and W combined with the  new snow to form shallow, soft slabs of around 4-10 inches, these will likely be thicker near ridge tops where wind speeds were higher.  Cornices are becoming very large right now as well. Avoid traveling on corniced ridge lines as they have the potential to fail quite a ways back from the edge.  Some areas have cornices that are overhanging more than 20 feet.

 

 

 

 

advisory discussion

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

Your Observations are extremely helpful and appreciated by all backcountry users.  If you have not checked our our Observations page, it is really easy to add snow or avalanche info.  Drop down menus and prompts will lead you through it and it is easy to add photos.

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

Our snow pack is deep and still getting deeper.  Yesterday we traveled to the Fisher Saddle area and had around 12-14 feet of snow just above the saddle at 7,600 feet. Along the road to the saddle, we saw a lot of debris from last week, and some fresh debris from yesterday morning's Sun. Our pit and hasty tests showed between 4 and 18 inches of unstable snow resting on the older snow below.  A couple weak layers exist in the upper snow pack and may be sensitive to the weight of a skier or snowmobiler.  A deeper layer of mixed graupel and decomposing facets was still present just about 3 feet down in the snow pack should be in the back of your mind if you are starting to poke into steeper terrain in the next few days.  Below the 4 foot mark the snow pack is very dense and well consolidated. 

Natural avalanche activity occurred yesterday On an East slope above the Fisher Saddle Road with the snow getting overheated by the morning Sun.  Pit tests and quick pits showed these layers to be moderately reactive and did not propagate in an extended column test. Shady, wind protected, slopes are suspect to have had a chance to grow Surface Hoar and/or facets prior to the storm. 

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 13 deg. F.
Max. temperature in the last 24 hours: 27 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 2 mph
Maximum wind gust in the last 24 hours: 11 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

 

Area Forecast Discussion
National Weather Service Boise ID
248 AM MDT Mon Mar 11 2019

.SHORT TERM...Today through Wednesday...Other than patchy morning
fog today will be sunny and slightly warmer than yesterday, under
dry northeasterly flow around an incoming short wave upper ridge.
Clear and cold again tonight as the ridge passes through, then wet
Tuesday as a storm comes in from the Gulf of Alaska. System will
bring widespread pcpn in the form of snow in the mountains, mixed
rain and snow in most southern valleys, and rain in the lowest
valleys including the Treasure Valley. Snow amounts in the
mountains will not be excessive, generally 2 to 4 inches in the
north and 1 to 3 inches in the south. Surface cold front will
pass through eastern Oregon early Tuesday afternoon and western
idaho late Tuesday afternoon and evening. No thunderstorms are
expected with the frontal passage, but winds will shift to northwest
20 to 30 mph, diminishing Tuesday night. Northwest winds will
increase again Wednesday, possibly reaching advisory speeds in
south-central Idaho, including the Upper Treasure Valley, western
Magic Valley, and south to the Nevada border. This increase will
be due to alignment of surface winds with strong NNW flow aloft
behind the exiting upper trough. Temperatures will continue below
normal through Wednesday.

.LONG TERM...Thursday through Monday. With the exception of a few
weakening shortwaves passing to the north, the extended looks fairly
quiet. These shortwaves will bring little more than passing cloud
cover to the CWA. By Sunday there is good model agreement of a
strengthening ridge developing across the western coastline. While
temperatures will be steadily increasing through the entire period,
they will rise to above normal for Sunday and Monday at least.

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.AVIATION...Mostly VFR, with patchy fog during the overnight
hours in some mountain valleys. Surface winds: generally
south/southeast at 10 kts or less. Winds aloft near 10 KFT MSL:
west/southwest 5-10 kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Sunny, with a high near 36. Light and variable wind. Clear, with a low around 17. South southwest wind around 5 mph becoming calm in the evening. Snow, mainly after noon. High near 33. Light and variable wind becoming south 5 to 7 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible
Temperatures: 36 deg. F. 17 deg. F. 33 deg. F.
Wind direction: Variable SSW South
Wind speed: Light 5 5-7
Expected snowfall: 0 in. 0 in. 1-2 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Sunny, with a high near 26. Wind chill values between -2 and 8. Southwest wind 9 to 11 mph. Mostly clear, with a low around 17. Southwest wind 13 to 16 mph. Snow, mainly after noon. High near 23. Breezy, with a south southwest wind 17 to 22 mph decreasing to 7 to 12 mph in the afternoon. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 26 deg. F. 17 deg. F. 23 deg. F.
Wind direction: SW SW SSW
Wind speed: 9-11 13-16 17-22
Expected snowfall: 0 in. 0 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.