Skied south of Cooke today. Got an ECTP28 down 80cm on small facets above a MF crust that was buried on March 14. West aspect at 9500'. While filling in the snowpit I got a large collapse. This is the same layer we were getting ECTP results on earlier this week north of town.
We rode into all three Yellow Mule drainages and the head of Muddy Creek. It was snowing hard and wind was blowing strong this morning. In the afternoon, clouds lifted and snow let up. Skies remained mostly cloudy, but with high clouds there was decent visibility at the end of the day. There were 10-12" of new snow since last weekend, 2-4" low density fell this morning.
There was a small wind slab avalanche in McAtee (Photo) and a small wind slab in Beaver Creek.
We dug four snowpits, northerly aspects (one in each Yellow Mule), and one on a southeast aspect on the west side of the Second Yellow Mule. We did not find any unstable test scores or concerning layers. ECTNs within the new snow and ECTXs in some cases. In the southeast facing pit there was one .5" thick crust below this week's snow and a crust 2" thick below last weekend's snow (photo). Most pits had a dirt layer from last Sun/Mon strong-extreme winds, 10-12" deep. Total snow depth was 6-7 feet.
<p>In the mountains around Cooke City, Island Park, and West Yellowstone, including the Southern Madison and Southern Gallatin Ranges, strong winds will drift recent snow, loading slopes where triggering <strong>wind slab avalanches </strong>that break 1-2 feet deep<strong> </strong>are likely. Continued snowfall and increasing winds will exacerbate this instability today. On Thursday, snowmobilers in Island Park reported that drifted snow and cornices cracked and collapsed easily on test slopes (<a href="https://www.mtavalanche.com/node/34706"><span>observation</span></a>). Avoid steep terrain where active drifting, cornices and shooting cracks indicate instability. Select slopes sheltered from the wind—often found at middle and low elevations where the trees block the wind—for safer avalanche conditions.</p>
<p>In the Lionhead area, and Southern Madison and Southern Gallatin Ranges, weak layers buried in late January continue to result in infrequent <strong>persistent slab avalanches</strong>. The most recent slide in the Taylor Fork occurred Wednesday and broke 2-4 feet deep (<a href="https://www.mtavalanche.com/node/34697"><strong><span>details</span></s…;). These layers have not resulted in avalanches in the Centennial Range, but snowmobilers assessing for instability noted a weak layer buried two feet deep below a melt-freeze crust that broke and propagated in unstable test results. Manage the problem of avalanches failing on persistent weak layers by selecting less consequential terrain (smaller slopes with fewer terrain traps) and following safe travel practices (beacon, shovel, probe, and traveling one at a time on steep slopes). Testing for instability can reduce, but will not eliminate, the chances of a surprise.</p>
<p>The danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>
<p><span><span><span>Windy conditions in the mountains around Bozeman and Big Sky will cause the limited snow available for transport to drift into slabs that could avalanche on steep slopes. The terrain immediately below cornices and on upper-elevation slopes loaded by west and southwest winds is the most likely area to trigger a <strong>wind slab avalanche</strong>, breaking 6 inches to a couple of feet deep. On Wednesday, a skier was caught and carried 100 feet down a steep slope south of Bridger Bowl, serving as a poignant reminder of the power of a relatively small slide (<a href="https://www.mtavalanche.com/node/34703"><strong><span>details and video</span></strong></a>). Yesterday in Beehive Basin, Ian recommended identifying and avoiding wind-loaded slopes and digging down a couple of feet to test for instability, reducing the chances for surprises if you are considering travel in steeper terrain (<a href="https://www.mtavalanche.com/node/34715"><strong><span>observation and video</span></strong></a>). Shooting cracks and recent avalanche activity are the most precise indicators of instability. </span></span></span></p>
<p><span><span><span>Seek out terrain sheltered from the wind where avalanche conditions are generally safe, and slides are unlikely. The danger is MODERATE on wind-loaded slopes and LOW on all others. </span></span></span></p>
Took a quick trip up Beehive Basin to the prayer flags, down into the meadows towards Bear Basin and returned the way we came.
Found around 4" of new snow from yesterday. There were scoured areas near the ridgeline on the west face, but we didn't find any cohesive wind drifts.
We dug two quick pits on the east facing terrain dropping towards Bear Basin. In our upper pit (NE aspect, 9200 ft), we found a layer of small facets (1 mm) buried a foot down, under the snow that has fallen in the past week. It didn't react in our Extended Column Test (ECTN25), but we hadn't had any reports of these facets previously, so it was a little bit surprising. We dug again, a little lower (~8900) to see if we would find it again, but it didn't exist in that location (instead there was a stout melt-freeze crust under this weeks snow).
There was a thin, breakable, melt-freeze crust under yesterday's 4" of new snow on any slope that wasn't a little shaded. Slopes with a northward tilt, or in the shade of trees, didn't have the breakable crust.
Despite high clouds, the snow surface was starting to get damp in the early afternoon and there were roller balls beneath our ski tracks. We saw a fresh wet loose slide on an low elevation west facing slope in Bear Basin.
