Avalanche Advisory published on February 1, 2020 @ 7:32 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Hazard is Moderate today.  Natural and human triggered avalanches were reported earlier this week as the snowpack adjusted to wind and storm loading.  Avalanches are possible today on several weak layers in the upper 3 feet of the snowpack. Wind slabs have been widespread in high north facing terrain throughout the week.  Pay attention to the effects of warming temps through the day; roller ball and point release activity are signs of decreasing stability.

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
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Local Snotel sites and ski resorts reported another 2+ feet of snow in the last 9 days. Temperatures fluctuated quite a bit during this time with very warm days occurring Sunday and Monday mid storm.  The effect was predictable with avalanches on steep terrain occurring naturally in the new snow layers.  The last 3 days of warm temps and sun have allowed the snowpack to stabilize quickly. 

There are still several layers of concern within the upper snowpack most notably being at least one layer of grauple mixed into the new snow layers.  Investigation reports of some of the Lick Creek Avalanches also showed a layer of buried surface hoar and or near surface facets below the new snow that was responsible for several R3D2 sized avalanches.  These layers show the ability to propagate and could result in an avalanche 1-2 feet deep.  Play it safe today, avoid steep slopes and utilize good travel protocols while you enjoy the deep snow.  

Pic 1 shows the upper snowpack instability near S. Bruin Mt. on Thursday, tests showed a reactive layer of grauple at 14 inches and a less reactive layer of near surface facets at 26 inches down from the surface.   Pic 2 shows the windslab instability yesterday on N. Bruin Mt.  The nearly bomber snowpack was very dense and the top 3-6 inches was pretty wet from warming temperatures and a semi freezing mist/fog that was the theme for most of the day yesterday. The weak layer yesterday was the softening 3-6 inch windslab.  The grauple layer was much less reactive here than it was on Thursday.


Avalanche Problem 2: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Expect to see sensitive wind slabs from a few inches to over a foot thick on a variety of upper elevation slopes.   Winds have been calm the last 2 days but winds earlier in the week they were out of the NE, N and NW and moved a lot of snow.   Overnight N and NW winds increased into the high teens. With additional snow and wind forecasted for tonight, expect to see some fairly dense wind slabs forming overnight tonight. 

Look for wind slabs near ridgetops, under corniced ridgelines and other wind exposed slopes.  In your face signs like cracking under your skis or snowmobile, a sudden change in how far your skis or sled are sinking in (ski/sled penetration) or obvious visual clues like rippled or sculpted snow  are all great indicators of wind slabs.  During the heat of the day today, it is possible we could see large cornices fail under their own weight.  Avoid traveling on or under corniced ridgelines, some cornices are getting pretty large and can fail further back than you expect.



advisory discussion

*Snowmobiliers, the Granite Mountain closure went is in effect from January 15-March 31. Please respect Brundage Catski terrain closures which are CLEARLY marked on the west side of Goose Lake.  There is a shared use route at the northern end of the closure to allow access to Granite Mt Lookout and the upper east face of Granite Mt.  Additionally, public motorized use of ANY other Catski road is not permitted, including the roads between Brundage Reservoir and the East side of the Goose Lake Road in the Slab Butte and 76 areas. Please respect closed roads and areas and only ride on open roads and in open terrain.  There are also other areas that are closed to snowmobiling in the West Central Mountains. Click here for the Payette National Forest Winter Travel Map.

*Note to skiers accessing Jughandle Mountain from Silver Fox Trail.  Please park in signed areas only. Blocking or narrowing the road could result in loss of access to this area, ticketing or towing by Valley County.  There is NO parking allowed on the East side of the road or in the snowplow turnaround.  If you can't park in the signed area, park further down the road in a place where you are not obstructing traffic.

recent observations

We traveled to Upper Hazard Lake and N. Bruin Mt. yesterday to check out some steep terrain and the effects of last week's wind on NW and W facing upper elevation terrain.  Freezing fog made for some very challenging riding conditions as it coated our goggles every 30 seconds.  A combination of warming, high humidity and the mist/fog made it a very wet and sloppy day as well.  The snowpack in this area traveled surprising deep and fun still in the lower/middle elevations on snowmobiles and quickly densified and traveled  much more shallow as we climbed up near 8000 feet.  Wind exposed terrain showed us widespread windslabs that were stabilizing rapidly and wind affected snow that was somewhat punchy(challenging skiing conditions) but surprisingly stable with the exception of the upper 3-6 inches.  Given the moisture in the snow and warming temperatures today, I would not expect to find good skiing in very many places.  Snowmobiling or riding groomers at the resort might be your best bet today.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 28 deg. F.
Max. temperature in the last 24 hours: 31 deg. F.
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: 19 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches

Area Forecast Discussion
National Weather Service Boise ID
324 AM MST Sat Feb 1 2020

.SHORT TERM...Today through Tuesday...A relatively flat upper
level ridge will pass over the region today, helping to warm temps
up to 10 to 15 degrees above normal. Southeast to southwest winds
will become breezy this afternoon. The warmth won`t last long,
however. A strong system coming toward us from the northwest will
bring a significant cold front and rain/snow Sunday and Sunday
night. A winter weather advisory has been issued beginning at 5 am
MST (4 am PST) Sunday morning for a large area along and near the
Nevada border Sunday and Sunday night. Snow amounts of 1-3 inches
in the lower elevations and 3 to 5 inches in the higher terrain,
along with wind gusts of 20 to 45 mph, will create travel
problems. Locations in the lower terrain from Baker County south
and east through the Snake River Plain will see rain rapidly
change to snow as the system moves southeast Sat night into
Sunday. Accumulations are expected to be less than an inch in
these locations. In the western Magic Valley, Jerome is only
forecast to get about an inch, but south toward Twin Falls,
amounts are forecast to be close to 2 inches. Monday through Tue
will be mainly dry and much colder, with temps around 5 degrees
below normal.

.LONG TERM...Tuesday night through Friday...Strong northwest
winds aloft will carry in the next round of abundant moisture for
SE Oregon and SW Idaho by early Wednesday. Widespread
precipitation should begin as all snow due to precedent cold air
in place. Throughout Wednesday, however, warmer and drier air from
an E Pacific ridge will start to nudge eastward into the western
U.S. Consequently, snow levels will gradually rise from west to
east over the area, and the precip will shift to mainly Baker
County and the central Idaho mountains late Wednesday and
Thursday. This nudge of warmer air will support milder
temperatures with snow levels 4500-5500 feet MSL by Thursday
afternoon. Thereafter, models diverge on the timing and intensity
of the next cold low pressure system that is expected to bring
showers and breezy winds by the end of the forecast period. The
current forecast suggests this strong cold front will arrive by
Saturday, but is subject to change as timing gets closer.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Mostly cloudy, with a high near 39. South wind 5 to 8 mph Rain and snow, becoming all snow after midnight. Low around 24. South wind around 6 mph becoming light and variable after midnight. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible. Snow, mainly before noon. Temperature falling to around 21 by 5pm. West northwest wind 3 to 8 mph. Chance of precipitation is 90%. New snow accumulation of less than one inch possible.
Temperatures: 39 deg. F. 24 deg. F. 21 deg. F.
Wind direction: S S WNW
Wind speed: 5-8 6 3-8
Expected snowfall: 0 in. 1-3 in. Trace in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: A 20 percent chance of snow after 11am. Mostly cloudy, with a high near 32. South southwest wind 14 to 17 mph. Snow. Low around 14. South southwest wind 8 to 16 mph becoming northwest after midnight. Chance of precipitation is 100%. New snow accumulation of 3 to 7 inches possible. Snow, mainly before 11am. Temperature falling to around 10 by 5pm. North northwest wind 9 to 13 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 32 deg. F. 14 deg. F. 10 deg. F.
Wind direction: SSW SSW NNW
Wind speed: 14-17 8-16 9-13
Expected snowfall: 0 in. 3-7 in. 1-2 in.

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.