Avalanche Advisory published on March 14, 2020 @ 7:05 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Hazard is Moderate today.  New snow accumulations accompanied by gusty winds will create new avalanche problems.  Expect to see shallow, very sensitive wind and storm slabs sitting on a variety of old snow surfaces including crusts, faceted snow and in some areas pockets of surface hoar.  Enjoy the refresh on the snow this weekend but take time to refresh your avalanche mindset. New snow equals new avalanche problems.

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

Winds started picking up yesterday afternoon and increased overnight.  Enough new snow has already fallen overnight to be easily transported by the 20-30 mile per hour gusts.   Wind directions have shifted from ENE to WNW so there will be newly formed wind slabs on a variety of aspects.  Some of these will have formed above stout sun crusts, older wind slabs or wind crusts, on older faceted snow and in some areas may be resting on surface hoar that formed earlier this week.  Use caution as you are approaching ridgelines on all aspects.  Look for visual clues today like drifts, dunes or areas where old tracks disappear into fresh snow on the mid to upper portion of a slope.

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

New snow after a high pressure cycle usually brings new avalanche problems.  Today, in addition to wind slabs, expect to see shallow storm slabs that are easy to trigger whether you are riding or sliding.  Sluffing on steeper terrain will also be likely with a variety of firm surfaces below the new snow. Dial back your terrain choices today and enjoy the new snow on lower angle slopes.

advisory discussion

If you see or trigger avalanches, please take the time to snap a picture, note key features of the slide as well as an estimate of aspect and elevation.  Your observations help us paint a better picture of what is happening across the PAC advisory area.  You can submit an avalanche or snowpack observation at: click on the menu link for observations then either avalanche or snowpack.  It is SUPER easy, takes 5 minutes and can be as detailed or limited as you want.  

recent observations

We toured up Diamond Ridge yesterday to get a look at more northerly terrain and see how the increasing winds were affecting the north aspects. The snow was mostly still soft on shady, north facing terrain and the sun never warmed up the south facing crust enough to make it skiable.  The winds increased by late afternoon and the partly sunny day marked the end of the high pressure cycle we have had for the last week. 

We found a variety of old snow surfaces including some areas with well developed near surface facets and some pockets of preserved surface hoar.  Mostly, the old snow surfaces are variations of crusts.  Wind board and wind crust was prevalent on exposed ridges and varying thicknesses of sun crusts were present on all but the most northerly terrain.  Yesterday we could not get snow to move anywhere.  Our pit tests showed green light conditions and ski cuts did not show any results.  Today will be a different story, all of these old snow surfaces should indicate a surface that will not promote bonding of new snow.  Forecasts vary from around 6 inches at 7600 feet to nearly a foot depending on where you look today but combined with wind, conditions just went from green light to yellow which means a return to heightened avalanche protocols and a return to cautious terrain and travel choices.


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: 29 deg. F.
Average wind direction during the last 24 hours: ENE
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 31 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches

.SHORT TERM...Today through Monday night...We will remain in an
active pattern over the short term. A large upper level low will
move south along the coast through the short term, ending up off
the coast of northern CA by Monday night. This will put our area
in southwest flow aloft, which typically brings warm air to the
region. In this case, cold air will filter in from the northwest
and lower snow levels in and near Baker County and western Harney
County, while high snow levels (around 6000 ft) will continue over
eastern Owyhee County and Twin Falls and Jerome counties. The
atmosphere will become unstable this afternoon and evening across
these warm areas, and on Sunday all of the area will be unstable.
Therefore, the slight chance of thunderstorms was left in place
this afternoon in eastern Owyhee and Twin Falls and Jerome
counties, and expanded north and west into the Upper Treasure
Valley, Boise Mountains, and most of Owyhee County this evening.
The entire area was give a slight chance for Sunday and again
Monday. Winds have been gusting to around 30 mph this morning over
much of the area, and we expect this to last into today over far
southeast Oregon and southwest Idaho. A cold front will move
slowly through the area today, but unlike some of our recent
fronts, this one will actually have less wind behind it. PoPs were
generally raised with this new forecast, even above the NBM over
much of the populated areas. Increasing instability combined with
long-duration warm air advection were the most important factors
in that decision.

.LONG TERM...Tuesday through Saturday...An upper level closed low
will continue impacting the area through the first half of the
period. Showery conditions will prevail for much of the area as
this low makes a slow progression eastward through the end of the
week. A second upper low begins to drop south off the coast by
Friday leaving the area under unsettled and wet conditions. Models
are struggling on timing for this second low, but are in agreement
to keep the area under unsettled conditions. Temperatures are
right at or a few degrees above normal through the period.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers, mainly before 1pm. High near 38. South wind 6 to 9 mph. Chance of precipitation is 90%. Total daytime snow accumulation of 1 to 2 inches possible. A 50 percent chance of snow showers, mainly after 1am. Mostly cloudy, with a low around 27. South wind 5 to 7 mph becoming calm in the evening. New snow accumulation of less than a half inch possible. Snow showers before 1pm, then rain and snow showers. Some thunder is also possible. High near 39. Calm wind becoming south around 5 mph in the afternoon. Chance of precipitation is 80%. New snow accumulation of less than one inch possible.
Temperatures: 38 deg. F. 27 deg. F. 39 deg. F.
Wind direction: S S S
Wind speed: 6-9 5-7 5
Expected snowfall: 1-2 in. Trace in. Trace in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers. High near 24. South southwest wind 11 to 17 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 2 to 4 inches possible. Snow showers likely, mainly after midnight. Mostly cloudy, with a low around 21. Southeast wind 7 to 9 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible. Snow showers. Some thunder is also possible. High near 29. East southeast wind around 8 mph becoming south in the afternoon. Chance of precipitation is 90%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 24 deg. F. 21 deg. F. 29 deg. F.
Wind direction: SSW SE E then S
Wind speed: 11-17 7-9 8
Expected snowfall: 2-4 in. Trace in. 1-3 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.