THIS AVALANCHE ADVISORY EXPIRED ON March 24, 2016 @ 7:10 am
Avalanche Advisory published on March 23, 2016 @ 7:10 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger is Moderate today above 6000 feet. 8-13 inches of new snow fell over the last 48 hours on a variety of old snow surfaces including crusts and faceted snow. Heavy accumulations of Grauple have accumulated with the new snow. Watch for soft wind slabs in the upper elevations and plan for small fast moving loose, dry avalanches on all slopes over 35 degrees.

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

The last 2 days have brought us some NW and W winds that gusted into the mid 30mph range on Monday and were in the mid to upper teens yesterday.  These winds will have loaded some of the Easterly aspects more than normal with some loading possible on the SE aspects as well.  Pay attention to the snow surface and where the new snow was deposited. Look for the obvious signs of wind transport and cornice growth but also for new pillowy deposits where they were not any last week. Fresh windslabs will be in the 4-16 inch range and should be pretty soft in most areas.  Some of these slabs may be sitting on layers of grauple or on the melt freeze crust from last weekend's tropical heat. Older, stiffer windslabs may still be encountered on E, NE, N or NW slopes as well.

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

Today's loose. dry sluffs are going to be Saturday's loose, wet slides which has been the pattern for the last few storm cycles we have seen this month. Temperatures and wind cooperated to leave us with a mostly non-cohesive layer of new snow over the crusts and remaining pockets of dry snow that made up our snow surface over the weekend. While we did not grow a cohesive storm slab over the last 2 days, we did get enough dry snow to create a new loose/dry problem.  Yesterday we got a decent amount of sluffing to occur near the ridges on all slopes over 35 degrees. The grauple accumulations added to the problem by providing several fat layers of ball bearings within the new snow. If you are riding or skiing in steep terrain, plan for and anticipate shallow and fast moving sluffing.  Don't let it steer you where you don't want to go and pay attention to terrain traps where these sluffs are going to pile up.

recent observations

Yesterday exceeded the precipitation totals in most areas, I took advantage of the spring powder by riding the chairs at Brundage Mt. Resort for most of the day and hitting Sargeants Mt. in the afternoon. We had free refills on the snow all day with new snow filling in our tracks on the ridge each run. We also had several periods of intense Grauple that added to the loose, dry sluff potential on the steeper slopes. In most areas there was about 6-8 inches of new snow above the melt freeze crust that was bonding relatively well by late afternoon. The new snow came in relatively dry as well and never got heavy throughout the day keeping the new snow right side up so it never truly formed a storm slab yesterday.  South Valley areas, got a little more clearing in the afternoon and slightly higher temperatures which likely created more of a cohesive slab in those areas.  Winds also were low to moderate through the day keeping new windslab growth to a minimum.  Overnight, winds picked up and may have transported some of the light snow into the NE,E, and SE aspects.  The key to staying safe is going to be to keep evaluating the snowpack as you travel through it.  Temperature, wind and precipitation totals vary quite a bit between different elevations and aspects with spring storms so don't let your guard down as you travel today. Remember, Moderate Danger means heightened avalanche conditions on specific terrain features, constant evaluation and re-evaluation of the snowpack is essential for safe travel today.  

Here are a couple of pictures of the intense grauple storms that deposited a thick layer of grauple throughout the afternoon yesterday.

          

Remember your information can save lives. If you see anything we should know about, let us know by clicking the OBSERVATION tab at the top of the page. Or by calling/emailing PAC forecasters at 208-634-0419 or forecast@payetteavalanche.org.

If you are getting out and enjoying any spring skiing/riding we would like to know. What did you see, how was the snow? Any information is good information!

weather

The "progressive" pattern called for by last week's weather forecasters has been very productive so far this week and temperatures have cooperated bringing another great week of spring powder for skiers and riders.  Look for partial clearing today with light NW winds becoming SW later in the afternoon and a high near 7600 feet around 36 degrees.  Tomorrow through Friday night will bring several small pulses of moisture which look like they will favor the Northern portion of the PAC advisory area with up to an additional 9-12 inches by Saturday morning.  Daytime highs will be in the mid to upper 30 degree range with a cool down on Friday. Winds will be increasing tomorrow and vary between NW and SW throughout the day adding to the wind slab problem on the Eastern side of the compass.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Cloudy, with a high near 40. Light and variable wind becoming southwest around 6 mph in the afternoon. A 40 percent chance of snow showers after midnight. Cloudy, with a low around 28. South wind around 5 mph becoming calm in the evening. New snow accumulation of less than a half inch possible. Rain and snow showers likely. Cloudy, with a high near 40. Light south wind becoming west southwest 8 to 13 mph in the morning. Chance of precipitation is 70%. New snow accumulation of less than one inch possible.
Temperatures: 40 deg. F. 28 deg. F. 40 deg. F.
Wind direction: Variable becoming SW S S then W/SW
Wind speed: 6 5 then calm in the pm 8-13
Expected snowfall: 0 in. Trace in. Trace in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: A 20 percent chance of snow showers. Cloudy, with a high near 36. Northwest wind 5 to 9 mph becoming southwest in the afternoon. Snow showers likely after midnight. Cloudy, with a low around 26. Southwest wind 10 to 15 mph. Chance of precipitation is 60%. New snow accumulation of less than a half inch possible. Snow showers. High near 36. West southwest wind 15 to 17 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 36 deg. F. 26 deg. F. 36 deg. F.
Wind direction: NW becoming SW later in the afternoon SW W/SW
Wind speed: 5-9 10-15 15-17 Higher in the northern portion of the advisory area.
Expected snowfall: Trace in. Trace in. 1-3 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.