THIS AVALANCHE ADVISORY EXPIRED ON March 11, 2018 @ 8:21 am
Avalanche Advisory published on March 10, 2018 @ 7:21 am
Issued by Dave Bingaman - Payette Avalanche Center
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Moderate Avalanche Hazard exists throughout the West Central Mountains, human triggered avalanches are possible today.  New wind slabs formed in the last 24 hours.  Older wind slabs from last week's storms still exist as well and may be overlying a weak layer of facets or in some areas a combination of crust and facets.  Watch for visual clues of where these new slabs have formed and where old wind slabs still exist.

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Last week's storm left us with wind slabs on a variety of aspects, some of these slabs are resting on a weak layer of snow above a well preserved crust.  This layer has produced human triggered avalanches in the last week.  While these slabs are not widespread, their ability to propagate and the unpredictable nature of their distribution should cause you to approach steep, exposed terrain with caution today and through the next few days. 

Yesterday we found 8-10 inch wind slabs in wind loaded upper elevation terrain that were overlying soft unsupportable snow below in.  While this is still a relatively thin slab, it is very sensitive and failed easily in pit tests.  These slabs are most likely to be found on upper elevation North through East aspects today but be aware that other aspects could also be harboring pockets of  wind slab on minor terrain features or where crossloading has occurred. Watch for visual clues of wind effect and manage your slope angles as you travel in wind affected terrain. These slabs should begin to bond as the temperatures increase over the next few days.

Avalanche Problem 2: Persistent Slab
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A layer of faceted snow exists above the February 4th crust  and around a series of sun and melt freeze crusts in some areas.  These layers have produced avalanches in windloaded areas over the last 2 weeks.  The layer of concern is now buried just about 2-3 feet down in the snowpack and has shown the potential to propagate easily when triggered by a skier or rider which is what happened on the W/SW aspect of Sargent's Mt. that produced a good sized avalanche last Sunday.  In some areas, this layer bonded to the new snow above and the crust has broken down or was very weak to begin with, in other areas. possibly more prevalent in the middle elevations 6500-7500 feet,  the crust and facet combo persists and should be taken very seriously.   The distribution of the layer is erratic and the only 2 ways you are going to insure your safety are by either digging in and finding out if this layer is present where you are riding or skiing or by avoiding slopes over 35 degrees.  You can also help minimize your risk by using good travel protocols and avoiding steep, rocky areas where the snowpack is less uniform and you are more likely to find a shallow trigger point.  

advisory discussion

Conditions are variable across the forecast area right now. Our advisory is based upon a small number of observations. Please let us know what you are seeing out there whether it is deep stable snow or avalanche activity. Observations can be submitted here. 

recent observations

Yesterday we toured in the Boulder Lake area and found a variety of snow types.  The warm temps in the previous 24 hours had already started to put a whammy on the lower elevation snowpack below 7000 ft.  Higher up the snow was still soft and carvable on sleds and made for some great turns on skis.  Our first pit was on a steep but somewhat protected north slope near Maloney Lake.  The snow on the southerly exposures had a thin sun crust on it and the softer snow on the northerly facing terrain had an uninspiring 8-10 inch thick wind slab perched over the soft and unconsolidated snow below. The wind slab failed easily in mit pits, ski cuts and in pit tests and we decided to find some more conservative ski terrain.   This northerly aspect near 8000 feet was also sporting the deepest snowpack we have seen so far this year with just over 12 feet of snow on the ground.  More protected and slightly lower northerly terrain inspired much more confidence and provided deep, soft snow and much better stability.  We were unable to find the crust and facet combo layer in the top 120cm of our pits yesterday in this area.

Photo below shows a 300cm probe in the bottom of a 70 cm pit.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 22 deg. F.
Max. temperature in the last 24 hours: 26 deg. F.
Average wind direction during the last 24 hours: W
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 24 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: 67 inches
weather

SHORT TERM...Ridging will bring warming aloft today through
Sunday, but surface warming will lag behind. We raised max
temps 2-3 degrees anyway, in order to correct a recent cool
bias. Skies will be mostly sunny today, except partly cloudy
along the Nevada border. A disturbance in the Pacific off
southern California will bring clouds from the southwest
tonight and Sunday. No pcpn is expected except for a slight chance
of rain or snow showers in Harney and Owyhee Counties overnight. By
Sunday afternoon the clouds will move to eastern Idaho and our zones
should become mostly sunny. The clouds will slightly warm
temperatures tonight in eastern Oregon, and slightly lower temps in
central Idaho Sunday.
Winds will be from the southeast 5 to 15 mph through Sunday,
except 15 to 25 mph between Mountain Home and Twin Falls, and
from the northeast at Jerome, ID.

.LONG TERM...Sunday night through Saturday...Good model agreement
that an unsettled weather pattern will take shape by the middle of
next week. An upper level ridge will keep rather mild temperatures
and dry conditions across the area through Monday night. The ridge
will give way to a Pacific trough Tuesday and Wednesday bringing
unsettled weather to the region. The first push of moisture is
expected to move into eastern Oregon Tuesday and spread across the
Idaho side Tuesday night and Wednesday. The main upper low is
forecast to track across northern and central California Thursday
and Friday. This will keep unsettled and showery weather over the
forecast area heading into next weekend. Tuesday temperatures will
be almost 10 degrees above normal then trend down to normal by
Thursday and a little below normal by week`s end.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Patchy fog before 8am. Otherwise, sunny, with a high near 44. Calm wind becoming south around 5 mph Mostly clear, with a low around 20. Southwest wind around 5 mph becoming calm in the evening. Mostly sunny, with a high near 45. Calm wind.
Temperatures: 44 deg. F. 20 deg. F. 45 deg. F.
Wind direction: S SW Calm
Wind speed: 5 5 Calm
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Sunny, with a high near 31. South wind around 6 mph. Mostly clear, with a low around 19. South wind around 7 mph Mostly sunny, with a high near 32. South southwest wind around 5 mph
Temperatures: 31 deg. F. 19 deg. F. 32 deg. F.
Wind direction: S S SW
Wind speed: 6 7 5
Expected snowfall: 0 in. 0 in. 0 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.