THIS AVALANCHE ADVISORY EXPIRED ON January 19, 2020 @ 7:22 am
Avalanche Advisory published on January 18, 2020 @ 7:22 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Hazard is MODERATE today. Moderate Hazard means that 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 snowpack.  These layers may be sensitive on some slopes but not on others.  Safe travel and careful snowpack 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
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You are most likely to encounter sensitive wind slabs in the upper elevations but given the amount of wind we have had over the last week, you could also find them at lower elevations.  Thursday, we were able to watch 30+ mph winds moving snow off peaks and ridges at multiple elevations. To further complicate matters, winds shifted quite a bit Thursday and early Friday am.  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 and choose your routes accordingly. 

Yesterday we found several 4-8 inch pockets of reactive wind slab on E and NE slopes with very stiff wind affected snow on N and NW slopes.  All were still cracking under our skis, the northerly slopes were much stiffer near the ridgelines.  Stiffer wind slabs allow you to get further out on them before they break, often times above you.  These were in fairly protected slopes near 7600 feet.  The upper elevations will have more widespread and potentially deeper wind slabs.  

Check out this cool avalanche video from Wednesday 1/15/20.  PAC volunteer  Matt Ganz caught a windloaded slope releasing on Beaverdam Peak while he was filming the gusty winds.  This slope is NE facing near 8500 ft.

 

 

https://youtu.be/9XLEWnWK_Vw

Avalanche Problem 2: Deep Slab
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Our deep slab problem right now is the perfect definition of  a LOW PROBABILITY/HIGH CONSEQUENCE scenario.  The likihood 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.

Thursday we found a well preserved layer of surface hoar 5 feet down in the snowpack on a high, north facing slope.  In addition, we found intact, 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 snowpack above them in this area.  We were also surprised to see a very large, recent crown that had released on one these layers near Victor Saddle during the wind loading earlier this week, likely the same day as the Beaverdam Slide.  

This picture was shot(low quality sorry) from about 1.5 miles north of Victor Saddle on 1/16/20.  Estimated crown height 6+ft on a NNW slope near 8400 ft.

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

We toured the ridgeline north of Brundage Resort to Sargeant's Mountain yesterday and found 3=6 inches of new snow and good ski conditions on most aspects.  The new snow that we received last weekend is bonding well to the old snow below.  The upper 12-18 inches of wind affected snow is stabilizing but still showing some potential for failure. We dug down to the ground and found rounding facets that did not fail in our tests.  Snow depths around 7600 ft averaged 140cm/55 in.  Cornices are getting big and are easy to spot on ridgelines in every direction.  We encountered some thin and reactive wind slabs on ENE and N facing terrain as well as some very stiff wind affected snow on the NNW terrain north of the Sargeant's summit yesterday.  While we lowered the hazard, Moderate hazard still implies dangerous conditions on specific slopes and the ability of humans to trigger them.  Your best bet is to travel using good protocols and avoid high consequence, wind loaded slopes.  Given the now more disbursed nature of our current problems, if you are entering steep terrain, your best bet is to look at the snowpack on each slope you intend to ride or ski.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 13 deg. F.
Max. temperature in the last 24 hours: 14 deg. F.
Average wind direction during the last 24 hours: WNW
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 17 mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: NA inches
weather

.SHORT TERM...Today through Tuesday...A disturbance will move into
eastern Oregon this morning, generating snowfall across the higher
terrain of Baker County, Oregon. Snow activity is favored to
spread across the West Central Mountains of Idaho by the afternoon
hours. Models have dampened the excitement this system previously
had, though the higher terrain of Baker County could see some
moderate snow accumulation by the time the system moves through
this evening. The exit of this system will allow a ridge to
amplify over the area leaving generally dry conditions into
Monday. Models have some agreement in showing the potential for a
weak bit of moisture to move into the area by Monday afternoon,
potentially creating some snowfall along the ID/OR border. Added
some additional precipitation to the forecast to account for this
potential. By Monday evening, this moisture will be mostly east of
the area, except for some lingering snow mainly over the Boise
Mountains. Tuesday remains another interesting day with a decent
swath of moisture expected to move into the area during the
morning hours. Activity will spread, with most areas seeing
potential for activity by the afternoon. Snow levels will keep a
bit more rain or mixed precipitation across the valleys.

.LONG TERM...Tuesday night through Saturday...Models are in fair
agreement over an upper trough impacting the Pacific Northwest on
Tuesday night. Precipitation is expected to spread across the
Intermountain West through Wednesday, resulting in snow at higher
elevations and rain/snow in the valleys. Model solutions spread
through the remainder of the extended, with the GFS favoring dry
conditions and the ECMWF/Canadian maintaining showers through the
end of next week. A chance of showers remains in the forecast beyond
Wednesday, with the greatest chance for snow across the West Central
Idaho Mountains. Temperatures through the extended will stay roughly
3-5 degrees above normal.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Snow likely, mainly after noon. Cloudy, with a high near 27. Calm wind becoming south around 6 mph in the afternoon. Chance of precipitation is 70%. Total daytime snow accumulation of 1 to 2 inches possible. A 20 percent chance of snow before midnight. Mostly cloudy, with a low around 21. South wind around 5 mph becoming calm in the evening. Partly sunny, with a high near 33. Calm wind.
Temperatures: 27 deg. F. 21 deg. F. 33 deg. F.
Wind direction: S S Calm
Wind speed: 6 5 Calm
Expected snowfall: 1-2 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow, mainly after 11am. Patchy blowing snow after 11am. High near 18. South wind 13 to 17 mph. Chance of precipitation is 80%. Total daytime snow accumulation of 1 to 3 inches possible. A 30 percent chance of snow, mainly before 11pm. Mostly cloudy, with a low around 15. South wind 7 to 13 mph. New snow accumulation of less than one inch possible. Partly sunny, with a high near 27. South wind 6 to 8 mph.
Temperatures: 18 deg. F. 15 deg. F. 27 deg. F.
Wind direction: S S S
Wind speed: 13-17 7-13 6-8
Expected snowfall: 1-3 in. Trace 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.