Avalanche Advisory published on March 13, 2020 @ 7:28 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Hazard is Low today.  Wet, loose avalanches may be possible on steep slopes that get direct sun, especially near exposed rock where the snowpack will be warming the fastest.  Isolated wind slabs are also something to think about if you are skiing or riding in steep northerly terrain, some of these wind slabs are resting on old crusts or faceted snow.  An experienced backcountry skier had a close call on 3/11/20 skiing a steep north facing gully. 

How to read the advisory

  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Loose Wet
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Temperatures in the upper elevations should be a little cooler today. Increasing clouds will also help to keep the snow a little cooler today.  Wet, loose avalanches will be possible as the sun hits East slopes this morning and works its way around to the west later in the day.   If you are traveling on or near steep southerly slopes, plan on being on cooler, more shady slopes before the sun melts the crust.  If you see roller ball activity increasing or notice that your skis or sled is sinking through the crust it is definitely time to find cooler terrain.  Yesterday we observed dozens of good sized wet, loose slides that occurred in the East and Middle Fork of Lake Fork Creek drainages over the last few days.  This activity seemed to be confined to the new snow layers we got last weekend. 

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

It is possible that if you are getting into steep you could trigger a wind slab.  While possible, these wind slabs are isolated to areas near or just below exposed ridgelines. Winds have been steady and from a variety of directions this week   An experienced backcountry skier took a scary ride on Wednesday near Blacktip when he encountered a 1 ft thick wind slab 2 turns into a confined, 40 degree gulley line.  Some of these slabs are resting on old crusts and faceted snow that formed during the last high pressure cycle.  


recent observations

George and I toured into the Boulder Backcountry yesterday and got up just about as high as the terrain would allow.  While we were somewhat goal driven to take advantage of the stable snow and mostly good ski conditions we also wanted to poke into the wind affected terrain and check the distribution of the wind slab problem.  We found a few pockets of wind slabs but could not trigger slabs with ski cuts or cornice bombs.  Sluffing was more of a problem in the soft snow on the steeper terrain.  Some of the pockets of wind slabs we did encounter were resting on a mixed layer of old faceted snow, new snow from last weekend with large grauple visible in the upper few inches.  Stability tests on these produced 2-6 inch shears that were dirty and lacked the ability to propagate farther than the  block or our skis. 

Remember Low Hazard means natural and human triggered avalanches are unlikely but small avalanches remain possible in extreme terrain. If you are skiing or riding in steep terrain, look at not only the snowpack but also the consequences of triggering even a small avalanche and whether you will have a safe route out if you do.  Even a small avalanche can have big consequences in steep or exposed terrain.  

Conditions will be changing tonight as a series of storms begin adding new snow to the existing snowpack.  Just in case you thought winter was over, the long term forecast shows a return to wintery conditions for the next 10 days. 


CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 18 deg. F.
Max. temperature in the last 24 hours: 27 deg. F.
Average wind direction during the last 24 hours: E
Average wind speed during the last 24 hours: 4 mph
Maximum wind gust in the last 24 hours: 19 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: NA inches

.SHORT TERM...Today through Sunday night...One last sunny, dry
day before an upper trough, currently just off the BC coast,
moves down the coast and brings widespread pcpn to our area.
The trough is forecast to become a closed low along the Oregon
coast late tonight, which will continue to move slowly south
down the California coast through next Wednesday. Moist
southwest flow aloft around the trough/low will begin pcpn in
western Baker and Harney Counties this evening, then spread
across all other areas overnight except south-central Idaho
where it will begin early Saturday. Pcpn will come in two
main surges, the first on Saturday and the second one during
the day Sunday. The air mass will destabilize Sunday afternoon
for a slight chance of thunderstorms. Snow level during pcpn
will range from near the valley floors in Baker and Harney
Counties to 5500-6000 feet in south-central Idaho. Total
snowfall will be 1-2 inches in most of eastern Oregon, 3 to 5
inches (but locally 8 inches) in the Boise Mountains and west
central Idaho Mountains, and 1-3 inches in the Owyhees and
southern Sawtooths. Temperatures will be a few degrees warmer
today, then cooler Saturday and Sunday due to pcpn and the lower
heights from the coastal upper low. Winds will be breezy
southeast today and Saturday with speeds 15 to 25 mph in the
Snake Basin, and 10 to 20 mph elsewhere during the afternoons.

.LONG TERM...Monday through Friday...Unsettled and wet conditions
for the region under the influence of an upper level low. This
low center will spin off the California coastline Monday sending
showers into the region. A slow progression eastward will leave
showers in the forecast through the end of the week. Snow levels
fluctuate throughout the period beginning around 3000 to 5000 ft
MSL before climbing above 5000 ft MSL by Tuesday evening, and
ending the period around 4000 ft MSL. Generally expect higher
elevation snow with valley rain. Temperatures will be above normal
for this time of year.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Partly sunny, with a high near 40. Light and variable wind. Snow showers after midnight. Low around 29. Light east southeast wind. Chance of precipitation is 80%. New snow accumulation of less than one inch possible. Snow showers, mainly before noon. High near 37. South wind 5 to 7 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible
Temperatures: 40 deg. F. 29 deg. F. 37 deg. F.
Wind direction: Variable SE S
Wind speed: Light Light 5-7
Expected snowfall: 0 in. Trace in. 1-2 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Partly sunny, with a high near 28. Light southeast wind becoming south 5 to 9 mph in the afternoon. Snow showers after midnight. Steady temperature around 26. South southeast wind 9 to 14 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible. Snow showers, mainly before noon. High near 23. South southwest wind 11 to 13 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 28 deg. F. 26 deg. F. 23 deg. F.
Wind direction: S SSW SSW
Wind speed: 5-9 9-14 11-13
Expected snowfall: 0 in. 1-3 in. 3-5 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.