Avalanche Advisory published on January 20, 2020 @ 7:04 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Danger is MODERATE today. Natural avalanches are unlikely today but human triggered avalanches remain possible especially on specific features or slopes.  You may trigger a wind slab on any wind loaded or leeward facing slope. You may also be able to trigger deeper avalanches on several other layers in the snow pack.  These layers may be sensitive on some slopes but not on others.  Safe travel techniques and careful snow pack evaluation are essential 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: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

You are most likely to encounter sensitive wind slabs in the upper elevations, on leeward slopes, especially on Northerly slopes that have seen the most loading and have sizeable cornices hanging above them, but to further complicate matters, winds shifted quite a bit Thursday and early Friday morning.  That means that wind slabs could be found on leeward features on just about any slope.  Look for the tell tale signs of wind effect like cornices snd other sculpting of the snow surface and choose your routes accordingly. 





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

Our deep slab problem right now is the perfect definition of  a LOW PROBABILITY/HIGH CONSEQUENCE scenario.  The chance of triggering is going down and becoming more and more isolated but still lingering.  Upper elevation slopes where early season snow was preserved is your likely best culprit.  Add uneven rocky terrain into the picture and you are increasing the chance of finding that landmine trigger point.  The size and density of the slab and the potential outcome of triggering one of these deep, persistent slabs is enough to keep me off of and away from the likely slopes.  These are the same layer that have been responsible for fatalities near the West Central Mountains and in several other areas this winter.

We have been finding a well preserved layer of surface hoar 5 feet down in the snow pack on a high, north facing slope.  In addition loose depth hoar and facets above and below the November crust that is now buried 7-8 feet down.  We generally do not see problem layers like these persisting with a deep snow pack above them in this area. 



advisory discussion

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

Yesterday, we traveled to the Northern end of the Payette to Upper Hazard Lake. We were able to observe a lot of terrain, and did not see any recent signs of avalanches in the morning. We hiked up Bruin's Western face that leads into Upper Hazard Lake. Our pit test results were limited to the upper 2 feet of the snow pack that is still loose and unconsolidated. The upper elevation snow surface took somewhat of a beating from the winds and had a 2-3 inch thick wind slab that made ski turns a little challenging in places. Up on the ridge I kicked a few cornices and had very little cracking and failures. Down in the trees, and in other Northerly areas that stayed protected the snow was much softer and did not have the thicker wind slab. 

The hanging cornices over the Northern slopes into Upper Hazard Lake are big and overhanging.

Around 2 pm the Sun started loosening up the snow surface and we observed multiple roller balls forming on sunny slopes, and we observed a natural point release on th road at Clough Point just past Brundage Mountain Resort.

South Slope near Brundage Reservoir.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 32 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: S
Average wind speed during the last 24 hours: 9 mph
Maximum wind gust in the last 24 hours: 24 mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: NA inches

Area Forecast Discussion
National Weather Service Boise ID
314 AM MST Mon Jan 20 2020

.SHORT TERM...Today through Thursday...Cloud cover continues to
increase this morning associated with moist southwest flow aloft.
As the upper ridge progresses eastward, a shortwave will move
across the region this afternoon. More models have come into
agreement over this disturbance, and the chance of precipitation
has increased across SW ID for this afternoon/evening. Southwest
flow aloft will be favorable for upslope snow in the West Central
Idaho Mountains, and light snow accumulations are anticipated.
Snow levels will remain near 4000 ft MSL during this initial wave
of moisture, resulting in rain showers or virga in the valleys. An
upper level trough will swing through the region on Tuesday,
causing widespread precipitation lasting into Wednesday morning.
Snow levels will stay between 3500-4500 ft, resulting in valley
rain and mountain snow. Snow accumulations will be roughly 2-4
inches across the West Central Mountains on Tuesday. Light snow
showers are expected to linger across the mountains through
Thursday as temperatures stay several degrees above normal through
the short term.

.LONG TERM...Thursday night through Sunday...Mild and moist
through the period as a series of Pacific storms moves
inland on fast zonal flow. Each storm will bring pcpn with
more in northern areas and only light amounts near the Nevada
border. Snow levels will be near 5000 feet each day, and
4000 feet at night, so valleys will have rain and northern
mountains will have snow but no major accumulations.
Temperatures will be relatively steady from day to day with
lows in the 20s in the mountains and upper 20s to mid 30s in
the valleys, and highs in the 30s in the mountains and lower
to mid 40s in the valleys.


.AVIATION...Mainly VFR this morning, deteriorating to MVFR this
afternoon from west to east, and locally IFR tonight in clouds
and pcpn. Mountains becoming obscured this afternoon and
tonight. Easterly surface winds up to 15kts, but northeast
20 kts near KJER. Winds aloft to 10k feet MSL, southwest
15-25kts through tonight.


Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: A slight chance of rain and snow showers after 11am. Mostly cloudy, with a high near 37. Calm wind. Chance of precipitation is 20%. A chance of rain and snow showers before 11pm, then a chance of snow showers. Cloudy, with a low around 29. Light south wind. Chance of precipitation is 40%. New snow accumulation of less than a half inch possible. Snow, mainly after 11am. High near 34. South wind 3 to 8 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 37 deg. F. 29 deg. F. 34 deg. F.
Wind direction: Calm S South
Wind speed: 0 Light 3-8
Expected snowfall: 0 in. less than one half in. 1-3 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: A 20 percent chance of snow showers after 11am. Mostly cloudy, with a high near 30. South wind around 8 mph. A 40 percent chance of snow showers. Cloudy, with a low around 21. South wind 8 to 10 mph. New snow accumulation of less than one inch possible. Snow, mainly after 11am. High near 23. South wind 10 to 13 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 30 deg. F. 21 deg. F. 23 deg. F.
Wind direction: S S S
Wind speed: 8 8-10 10-13
Expected snowfall: 0 in. less than one 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.