THIS AVALANCHE ADVISORY EXPIRED ON January 12, 2019 @ 7:16 am
Avalanche Advisory published on January 11, 2019 @ 7:16 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Hazard is Moderate today.  Wind Slabs and Cornices have formed on exposed slopes and vary in their reactivity to skiers and snowmobiles.  Some of the wind slabs are resting on Grauple and weak layers persist deeper in the snowpack. Use caution in areas where wind slabs are present especially where the snowpack is still shallow.  Loose/Wet Avalanches will be a consideration on slopes affected by the sun and warming temperatures over the next few days.

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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Wind Slabs are present in many upper elevation, wind exposed areas. Given the warming temperatures, these slabs should begin to stabilize fairly quickly BUT in some areas these slabs are resting on a layer of Grauple and our Persistent Weak Layer of Basal Facets.  You are most likely to trigger these wind slabs on high, northerly, leeward slopes but be aware of smaller terrain features  like gullies that have experienced cross loading especially on East and West aspects. We got just enough new snow on most of these new wind slabs to camouflage them so you will want to pay attention to how your skis or sleds are traveling on the snow and how the snow feels in wind affected areas.  A quick mit pit, pole test or even stepping off your sled will give you an indication of what lies below the surface you are traveling on.

On Thursday we toured into an area where we have been tracking both the effects of the wind in the upper elevations and the Persistent Weak Layers in more protected areas in the middle elevations.  The photos below show 2 VERY different snowpacks:

The middle elevation shows the trend that we expected to see with the warming temps this week and an improving snowpack.  The Buried Surface Hoar  and Basal Facet Layers are rounding and gaining strength and the snowpack is getting deep enough  and strong enough to give us confidence in steeper terrain.

The upper elevation did not inspire the same confidence. We found a highly variable snowpack with thin rocky areas where the wind slabs were failing in isolation and in the moderate realm during our tests. More concerning was the lingering and reactive layer of Basal Facets that was well preserved at the bottom of the snowpack.  The  take home message is that while these areas are probably not the norm, you should still be wary of the upper elevation snowpack and avoid slopes steep enough to slide. avalanches triggered in the wind slabs have a small possibility of stepping down into the weak layer near the ground which would be very high consequence scenario.

Avalanche Problem 2: Loose Wet
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Unfortunately  the cold dry snow of the last few weeks came to an end this week. Temperatures warmed quite a bit and the snowpack did too.  Over the next few days expect to see increased Loose/Wet activity in the form of roller balls and point releases on steep slopes that are getting a good dose of the suns rays.  The first warm up during the winter sometimes produces a few natural avalanches on steep slopes as the snowpack warms so pay attention to what aspects you are choosing throughout the day.

We observed quite a bit of roller ball activity on the steep slopes above Clow Point yesterday afternoon as we were coming back in on the Goose Lake Road.

advisory discussion

Thanks to everyone that came out last night to support the Friends and share a pint at Broken Horn.  A  BIG thanks to Broken Horn Brewery for hosting and donating to  FPAC as well! 

Due to the partial government shutdown, avalanche forecasting will be limited.  We expect to forecast 3 times a week until the shutdown has ended.

Your observations are very helpful to the PAC staff and help create a better picture of the complex terrain in our advisory area.  You can click on the add observations linkand add as little or as much detail as you have.  It is easy to navigate and will also upload pictures easily.  Please contribute to your local forecast by sharing what you see or experience even if it is just good snow. or a trip report.

recent observations

We noted an increase in roller ball activity yesterday on slopes that were warming despite the lack of sun yesterday.  Expect to see some additional wet snow avalanches as the sun and temperatures decrease stability on Southerly slopes over the next few days. We also noted some cracking in the shallow wind slabs encountered mostly in upper elevation terrain.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 21 deg. F.
Max. temperature in the last 24 hours: 28 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 21 mph
New snowfall in the last 24 hours: na inches
Total snow depth: na inches
weather

.SHORT TERM...Today through Sunday...An amplifying upper ridge
will remain anchored over the interior NW through Sunday. As the
ridge persists, a strengthening inversion will act to gradually
cool temperatures and support fog/stratus development in
sheltered valleys and basins. Open valleys will see strong enough
winds in the boundary layer to minimize fog/stratus development
early on, but these areas could fill in over the weekend.

.LONG TERM...Sunday night through Thursday...High pressure aloft
will keep Sunday night dry. On Monday southerly flow aloft will
bring a chance of light snow to the southern CWA border. Moisture
will continue to increase from the south through the week as the
upper high moves away and Pacific troughs make their way inland..
Models indicate significant pcpn Thursday through Friday. Snow
levels then will range from 3500 feet MSL in the north to 4500
feet MSL in the south so pcpn will be rain in the populated
valleys, but significant snow in the mountains. Low temperatures
will slowly rise through the week under increasing cloud cover.
High temps will change little from day to day.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Patchy fog before 11am. Otherwise, sunny, with a high near 33. Calm wind. Patchy fog after 11pm. Otherwise, mostly clear, with a low around 9. Calm wind. Patchy fog before 11am. Otherwise, sunny, with a high near 33. Calm wind.
Temperatures: 33 deg. F. 9 deg. F. 33 deg. F.
Wind direction: Calm Calm Calm
Wind speed: NA NA NA
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Sunny, with a high near 30. South wind around 8 mph. Mostly clear, with a low around 20. South southeast wind around 7 mph. Sunny, with a high near 33. South wind around 6 mph.
Temperatures: 30 deg. F. 20 deg. F. 33 deg. F.
Wind direction: S SSW S
Wind speed: 8 7 6
Expected snowfall: 0 in. 0 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.