Posted:
Dec 6, 2014 @ 10:23 am

Good morning, this Dudley Improta with a snow conditions update for December, 6, 2014. We will begin regular avalanche advisories on Friday, December 12.

Warm mountain temperatures have helped stabilize the snowpack in our area. Weather and SNOTEL stations this morning are showing temperatures just above freezing at elevations up to 6000 feet and temperatures in the high 20’s up to 8000 feet. The Stuart Mountain SNOTEL shows that the Rattlesnake snowpack  has settled 3 inches in the last 48 hours. These are good signs for stability.

We were able to clean the rime off the wind speed and wind direction devices on Point Six yesterday. The station indicates southwest winds changed to east and southeast winds last night. The winds have been blowing 8 to 17 mph.

Steve could  get the facets that formed in November to fail yesterday in snow pits;  but the failures were not showing much energy. All this is good compared to what we were hearing 10 days ago.

There is always some avalanche problem to consider. For now I would still not trust the facets on the  bottom of the snowpack. I would be particularly wary of areas with relatively shallow snow and areas with rocky outcrops or cliffs. Rock  formations typically hold these facets for a long time. The other possible problems might be loose wet snow sluffs or small wind slabs.

Weather Forecast and Avalanche Outlook

A fast-moving system is predicted to pass through the region tonight. This disturbance could produce higher winds and up to 6 inches of snow at elevations above 7000 feet. This storm could increase the chances of wind slabs on leeward slopes at the higher elevations.

Early Season Tune-up

The snow has arrived and the early season “keeners” have already been logging vertical. Take some time to go through your avalanche gear and make sure you’re ready for recreating in the mountains.
1. Check your transceiver(s) and put in fresh batteries; check for corrosion. Run through a few practice drills with your transceivers.

2. Pull out your probes and shovels and put them together. Consider putting a little lubrication on the joints and parts that fit together. Check your shovel blades and shafts for cracks or weaknesses.

3. Go through your “possibles” ; your first aid and repair kits. Clean them out, reorganize the contents, make sure you have what you think you may need. Check your fire starting kit; perhaps put in fresh materials.

4. Meet with your backcountry partners and practice several rescue scenarios, including multiple burials, deep burials, probing, and shoveling.

5. Look into avalanche training if you haven’t already taken a course. If you’re going to ride or ski slopes over 30 degrees you can never be 100% sure the slope won’t fail. You need to hedge your bets.

6. Maybe take that 3-year-old power bar out of your pack and put a new one in.

READ FULL ADVISORY  

Problem 1 - Wet snow sluffs

  • TYPE

    loose-wet

    Loose Wet

    Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose-Dry Avalanches,they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose-wet avalanches can trigger slab avalanches that break into deeper snow layers.

  • SIZE

    2-3

    1 (Small)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-3

    Possible

    The likelihood of an avalanche resulting from this problem.

Wet, loose snow could sluff on steep (>35 degrees) terrain.

Problem 2 - Lingering wind slabs

  • TYPE

    wind-slabs

    Wind Slabs

    Release of a cohesive layer of snow (a slab) formed by the wind.  Wind typically erodes snow from the upwind sides of terrain features and deposits snow on the downwind side.  Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

  • SIZE

    2-3

    1 (Small)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-3

    Possible

    The likelihood of an avalanche resulting from this problem.

High elevation (>7000 feet) leeward slopes may harbor wind slabs. The storm predicted for today may increase the chances of wind slabs.

Problem 3 - November facets

  • TYPE

    deep-persistent-slabs

    Deep Persistent Slabs

    Release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer, deep in the snowpack or near the ground.  The most common persistent weak layers involved in deep, persistent slabs are depth hoar, deeply-buried surface hoar, or facets surrounding a deeply-buried crust. Persistent, Deep-Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage. They commonly develop when Persistent Slabs become more deeply-buried over time.

  • SIZE

    5-6

    2-3 (Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-2

    Unlikely/Possible

    The likelihood of an avalanche resulting from this problem.

Relatively shallow snow depths,  rocky outcrops and cliffs may hold November facets for a longer period.

FORECAST & OUTLOOK

A fast-moving system is predicted to pass through the region tonight. This disturbance could produce higher winds and up to 6 inches of snow at elevations above 7000 feet. This storm could increase the chances of wind slabs on leeward slopes at the higher elevations.

This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.