21-22

Chris Hericks, snow ranger on Beaverhead Deerlodge NF, points to the lower of two surface hoar layers. We are finding similar layering throughout our entire forecast area. The top 18" of the snowpack is weak and will quickly become unstable when it snows. Photo: GNFAC

Lionhead Range, 2022-02-10

Large whumpfs and collapses near Cooke

Wyoming Creek
Cooke City
Code
Elevation
9242
Aspect Range
E-SE
Latitude
44.98990
Longitude
-109.96500
Notes

I was touring on the west side of Wyoming creek today. Got some large whoomfs and collapses on the Ridgeline and a poor test score of ectp11 q1 sp 22cm deep on on buried surface hoar on top of facets on an E/SE facing slope at 9242' hs-163cm, slope angle 26°  The same layer was easily identifiable in hand shears throughout the day. 

Number of slides
0
Number caught
0
Number buried
0
Problem Type
Persistent Weak Layer
Weak Layer Grain type
Surface hoar crystals
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year

GNFAC Avalanche Forecast for Wed Feb 9, 2022

Snowpack and Avalanche Discussion

<p>Alex has been in Cooke City since Sunday after 12-14” fell; lucky boy. He and others noted natural and human triggered avalanches under the new snow where a thick layer (6+”) of weak snow (facets and surface hoar) continues to show signs of instability. Our <a href="http://www.mtavalanche.com/avalanche-activity"><strong><u>Avalanche Activity List</u></strong></a> documents 9 events in one week. Yesterday, as Alex skied, he witnessed shooting cracks, a whumpf and another day of propagating test scores in his <a href="http://www.mtavalanche.com/snowpits"><strong><u>snowpits</u></strong></…;. His latest <a href="https://youtu.be/EQDLaHsyinU"><strong><u>video</u></strong></a&gt; is an instructive show-and-tell of avalanche concerns.&nbsp;</p>

<p>Before Friday and Saturday’s storm, stability was good and people were feeling comfortable getting into serious avalanche terrain. Today, not so much. Avalanches are possible on the same slopes that were stable a week ago. We have a significant weak layer that has 1.5 feet of snow on top of it. Any slope that has a wind-load will be especially worrisome. Change objectives and stay clear of avalanche terrain at the first sign of instability, like Alex did yesterday. The weak layer is not going away and slopes still need time to adjust to the added weight of the weekend’s snow. For today, the avalanche danger is rated MODERATE on all slopes.</p>

<p>&nbsp;</p>

<p>The snowpack from the Bridger Range to West Yellowstone is generally stable. Most slopes have weak, sugary snow (and/or feathery surface hoar crystals) buried 18” under the surface. Without the weight of new snow this layer will remain dormant, but there are a few exceptions. Sprinkled throughout the forecast area are small, unstable slopes from wind drifting. Thicker, meatier drifts of snow could break on this weak layer. This is what occurred in Lionhead on Sunday. A snowmobiler triggered a small, shallow and very steep wind-loaded slope that carried him into trees and buried him (<a href="http://www.mtavalanche.com/node/25766"><strong><u>details</u></strong><…;). Even in a sea of stability there are a few shoals of danger lurking. There always are. A telltale sign of instability associated with wind-loading are cracks shooting out from skis or a sled. For today, given the lack of new snow and overall stability, avalanches are unlikely and the danger is rated LOW.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Education Opportunities

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming 

TOMORROW, February 10th, Forecaster Chat at Uphill Pursuits, “Beyond the Beacon”, 6:30 p.m., with GNFAC forecaster Dave Zinn.