THIS AVALANCHE ADVISORY EXPIRED ON February 7, 2019 @ 7:01 am
Avalanche Advisory published on February 6, 2019 @ 7:01 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Hazard is Considerable.  Human triggered avalanches are still possible in steep terrain. Gusty winds around 22 MPH out of the South West along with over 2 feet of new snow over the last few days, have created wind slabs that are not well bonded to the older snow.  Be smart, use safe travel protocols avoid steep terrain, and be aware of changes in the snow pack throughout the day on different aspects.  

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

2 Feet of new snow and gusty winds around 22 MPH out of the South West have created wind slabs that are not bonding to the older snow. Winds are now out of the North and are forecasted to gust into the 20's tonight. Wind slabs will develop on Southern aspects also.  Reports of human triggered avalanches have been coming in over the last few days on the new snow interface which is lying on some crusts and graupel.

Pay attention to wind stiffened snow near the ridge tops today, or places that show obvious wind effect in the form of ripples or small pillows. 

Do not let your guard down, be smart, use safe travel protocols including 1 at a time on steep terrain and be aware of changes in the snow pack throughout the day on different aspects.

This was submitted to us from a snowmobiler yesterday...Check out our observations page for more, or to submit one of your own.

 

Avalanche Problem 2: Storm Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Over 2 feet of new snow in the last few days has fallen, and is tending to be a bit thicker/slabby, especially near the old snow interface where it has bonded but not very well. Storm slabs will likely be found in protected areas today. 

Do not let your guard down, be smart, use safe travel protocols including 1 at a time on steep terrain and be aware of changes in the snow pack throughout the day on different aspects.

advisory discussion

PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.

Please be aware that there are areas that are CLOSED to motorized traffic in the McCall  and greater West Mountains area.  Just because there are tracks in some areas, does not mean they are open.  Please respect all users and closures.  See the Payette Winter Travel Maps for clarification.  Both the East and West maps can be downloaded on the Avenza app on your phone or are available at trailheads and local shops.   IT IS YOUR RESPONSIBILITY TO KNOW WHERE YOU ARE AND WHERE THESE CLOSURES EXIST.  

recent observations

Yesterday, we toured Squaw point on skis. Our 600's were challenged in the deep new snow to climb anything steep. Skiing and riding conditions were pretty much all time. We still are finding various depths of wind slabs that are far from bonded to the snow below them, and were cracking under our skis. The new 2 feet of snow is starting to bond to the older snow as seen in our test pits, but not as well as we would like it to. We were able to get failures on the old/new snow interface graupel layer in an extended column test that propagated across the block under hard hits on the shovel (ECT 29 @60 cm from the surface), and user reports are indicating that snowmobilers are still triggering this layer.  

Various users have submitted some really good observations that are worth checking out on our observations page. Reports of natural avalanches have calmed down, and we saw some evidence on the NE aspect of squaw point of a widespread natural avalanche (R3D2) where the debris was about covered up from the new snow.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 5 deg. F.
Max. temperature in the last 24 hours: 16 deg. F.
Average wind direction during the last 24 hours: W
Average wind speed during the last 24 hours: 2 mph
Maximum wind gust in the last 24 hours: 4 mph
New snowfall in the last 24 hours: 4 inches
Total snow depth: 72 inches
weather

 

Area Forecast Discussion
National Weather Service Boise ID
334 AM MST Wed Feb 6 2019

.SHORT TERM...Today through Friday...Early morning water vapor
satellite showing upper low center spinning into far southwest
Idaho with the back edge of the trough entering southeast Oregon.
These features continue to pull eastward today keeping a slight
chance of snow showers until they clear the region. While shower
development will focus over higher terrain, a flurry or brief
shower is possible at lower elevations through late morning.
Northwest winds ramp up this afternoon with the strongest winds
along the I-84 corridor from the Baker Valley through the Snake
Plain where gusts to 35 mph are possible. The winds and well below
normal temperatures will keep wind chills in the single digits in
the mountains and teens to low 20s at lower elevations. Winds
diminish overnight and with clearing skies low temperatures will
drop below zero in mountain valleys and into the single digits
and teens elsewhere. Thursday is dry, with slightly warmer
temperatures and much lighter winds as a weak upper ridge passes
over the area. Clouds increase Thursday night into Friday ahead of
the next storm system. By late Friday southeast Oregon and the
west-central Idaho mountains will see a chance of light snow.
Temperatures are several degrees warmer though still below normal.

.LONG TERM...Thursday night through Tuesday...Temperatures will
moderate to near normal over the weekend, ahead of the next upper
level trough, which will move out of northwest Canada Friday night
and arrive off the Pacific Northwest coast on Saturday. As the
trough winds inland, we can expect widespread snow showers
Saturday through Sunday. Most of the snow will fall over the
mountains, with total accumulations in the lower valleys around an
inch. Temperatures will cool to around 5 degrees below normal on
Monday. Another trough from western Canada will arrive over the
northern Intermountain Region on Tuesday with more snow showers,
again mostly over the mountains.

&&

.AVIATION...VFR except for areas of MVFR/IFR ceilings in the KBNO
and KMYL areas this morning. Surface winds west to northwest 10-15
kts this morning increasing to 15-20 kts this afternoon with
gusts to 30 kts through the Snake River Valley southeast of KBOI.
Winds aloft at 10k feet MSL northwest 10-20 kts increasing to
15-25 kts this afternoon.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Occasional light snow before 11am. High near 21. Northwest wind 5 to 9 mph. Chance of precipitation is 80%. Little or no snow accumulation expected. Mostly clear, with a low around -2. North northwest wind 5 to 8 mph becoming calm after midnight. Sunny, with a high near 22. Wind chill values between -1 and 9. Calm wind
Temperatures: 21 deg. F. -2 deg. F. 22 deg. F.
Wind direction: NW NNW Calm
Wind speed: 5-9 5-8 becoming calm 0
Expected snowfall: Little in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: Occasional light snow before 11am, then isolated snow showers after 11am. High near 10. Wind chill values between -5 and -10. North northwest wind 7 to 11 mph. Chance of precipitation is 80%. Little or no snow accumulation expected. Mostly clear, with a low around -2. Wind chill values between -9 and -14. North wind 7 to 11 mph, with gusts as high as 20 mph. Sunny, with a high near 13. Wind chill values between -2 and -12. Northwest wind around 6 mph becoming light and variable in the morning.
Temperatures: 10 deg. F. -2 deg. F. 13 deg. F.
Wind direction: NNW N NW
Wind speed: 7-11 7-11, Gusts to 20 MPH 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.