THIS AVALANCHE ADVISORY EXPIRED ON February 4, 2017 @ 6:07 am
Avalanche Advisory published on February 3, 2017 @ 6:07 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger is MODERATE today on steep, upper elevation slopes above 7000 feet where shallow, human triggered wind slabs are possible.  Loose, dry avalanches or sluffs are a concern on very steep terrain. Below 7000 feet the avalanche danger is LOW but will rise throughout the day with the arrival of a wet and windy storm. Natural and human caused avalanches will become likely with 15+ inches of snow forecasted in the upper elevations through 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
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Winds calmed down over the last 2 days, but moderate winds gusting upwards of 24 MPH out of the SSW earlier this week plus a few new inches of light snow helped form newer wind slabs up to 6 inches thick in the upper most terrain on multiple aspects. These new wind slabs may be resting on a slick crust  that has developed in the last week from the sun, and may be sensitive to the weight of a skier or rider. Be cautious in steep exposed terrain, where a small wind slab could knock you off your feet or push you where you don't want to go. Older wind slabs can still be found, but will be stubborn to trigger. Your best strategy is to simply avoid areas with obvious wind affect, drifts or rounded pillows of snow are great visual indicators.  Hollow or punchy feeling snow will also let you know you are on a wind slab. 

Today the winds are going to be increasing after noon, fresh wind slabs will begin to grow pretty quickly with plenty of light density snow to move around. Winds combined with heavy snowfall will continue to be a problem creating larger wind slabs over the next few days. 

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

Small, loose dry avalanches of sluffs have been increasing over the last few days.  If you are skiing or riding in steep terrain today, you will need to pay attention to what is chasing you down the hill.  While these small avalanches are not likely to bury you, if you are in consequential terrain they can easily steer or push you where you don't want to go.  As new snow accumulates above the light dry snow today and over the next few days, this will increase the storm slab potential especially in steeper terrain.

Avalanche Problem 3: Persistent Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

We are still tracking buried Basal facets, surface hoar, and near surface facets that are now buried in our snowpack. These persistent grain types can awaken after being dormant for an extended period of time (hence the name persistent). These layers are scattered and not widely distributed right now but can still be found on any protected slopes with a north tilt to them.  We have also found shallow rocky areas near ridgelines that are harboring some large basal facets now buried under old wind slabs. Our stability tests have shown that while these areas are hard to trigger, when they fail, they are failing near the ground with a hard slab above them.  While we haven't seen any activity in these layers for 2 weeks now, keep them in mind as you make your travel plans over the next few days and as we add weight to the snowpack. 

advisory discussion

The Friends of the Payette Avalanche Center (FPAC) needs YOU! We are in desperate need of more user support and financial assistance. The avalanche forecast is not a guaranteed service, and is in jeopardy of dwindling down to only a couple of days a week in the near future. Please help if you can by clicking the DONATE tab above. If you value this life saving information, make a donation or help the FPAC in raising funds for the future.

Snowmobiler/Snowbiker Travel Restrictions:  a quick reminder that the Granite Mountain Area Closure is now in effect.  In addition there are other areas on the Payette National Forest that are CLOSED to snowmobile traffic including Jughandle Mt east of Jug Meadows, Lick Creek/Lake Fork Drainage (on the right side of the road as you are traveling up canyon), and the area north of Brundage Mt Ski area to junction "V" and along the east side of Brundage and Sergeants' Mts. with the exception of the Lookout Rd( junction "S").  Please respect these closures and other users recreating in them.  Winter Travel Map(East side). You can download the map to the AVENZA app on your phone, and know your exact location while you are out riding. 

FOUND on Goose Lake Road Wednesday near Brundage Reservoir- prescription glasses in case.  Email us at forecast@payetteavalanche.org if these look familiar.

recent observations

Yesterday was another gray day with out much change in the weather or snowpack.  Light winds and 2-3 inches of new snow in the upper elevations made for good skiing and relatively low hazard.  Ski cuts on steep northerly terrain produced sluffing and nothing else. Thin and sensitive wind slabs can be found on exposed, upper elevation terrain.  Of most concern is the variation that we are still finding in the snowpack on upper elevation terrain where the snowpack is still shallow or has been scoured.  Persistent Weak Layers can be found in these areas and some protected terrain with a 1-3 foot slab above them and are remaining active in our pit tests. These variations are going to be something to keep in mind as we add more storm and wind blown snow above them.  See the video of a weak layer that we found Wednesday.

Over the last week, local recreationists have been bagging steep lines on skis and sleds with low consequence snow, but conditions are going to change today with the arrival of a powerful storm and your mindset needs to change as well.  The West Central Mountains seem to be in the Bull's Eye for a major precipitation event but the weather models are having a tough time agreeing on storm totals and temperatures.  Up to 3.5 inches of Snow Water Equivalent could hit the area by Monday afternoon which equates to a lot of higher density snow accompanied by high winds.  Pay attention to RAPIDLY changing conditions as the storm arrives especially Saturday and Sunday as temperatures climb...the avalanche danger will be increasing as well.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 23 deg. F.
Max. temperature in the last 24 hours: 23 deg. F.
Average wind direction during the last 24 hours: SE
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: 16 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: 74 inches
weather

Today through Sunday...Bands of snowfall present across southwestern Idaho this morning. Additional showers are anticipated as low pressure off the Oregon coast continues to push eastward. Prevailing southwest flow will help to usher moisture across the area, with the most favorable locations bring across eastern Oregon and central Idaho. Winter Storm Warnings in effect for the most susceptible areas, with advisories included for southeastern Oregon and into the Lower Treasure Valley. With snow ratios remaining generally less than 10:1 across the area under continued warming temperatures, wet and heavier snowfall remains expected across impacted areas. Model forecasted snow levels continue to be a challenge, especially across the central portion of Idaho where models are putting, more or less, a bulls-eye of snow levels above where they should be. 

Consequently, snowfall will weaken from west to east on Sunday, though activity over the central Idaho mountains will continue. The warming trend will continue on Sunday Temperatures to warm over the next couple days with many locations achieving temperatures above freezing. This will convert many areas of snow to rain, with brief periods of freezing rain possible during the conversion. Temperatures continue to warm on Saturday, with values approaching seasonal norms, especially across the Snake River Plain. Additionally, gusty wind is anticipated across much of the area on Saturday as the pressure gradient tightens in response to the advancement of the low pressure system moving south near the Washington coast.

                             

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Snow showers then snow. Snow Snow
Temperatures: 32 deg. F. 29 deg. F. 34 deg. F.
Wind direction: South SSW SSW
Wind speed: 6-11 Around 10 Around 11
Expected snowfall: 3-5 in. 3-5 in. 1-2 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Snow showers then snow Snow Snow
Temperatures: 29 deg. F. 22 deg. F. 29 deg. F.
Wind direction: SSW S SW
Wind speed: 21 to 31, with gusts as high as 43 23 to 25, with gusts as high as 34 23 to 25, with gusts as high as 34
Expected snowfall: 5-9 in. 4-8 in. 2-4 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.