19-20

GNFAC Avalanche Forecast for Mon Feb 3, 2020

Snowpack and Avalanche Discussion

<p>Since yesterday morning the Bridger Range received 14” of snow equal to 1.4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). Strong east wind drifted snow into thicker slabs that are easy to trigger. These slabs formed in less common locations, like along west facing ridgelines or upslope of rolling terrain on east aspects. Today avoid wind loaded slopes where natural avalanches are possible and human triggered avalanches are likely.</p>

<p>Yesterday Doug skied in the northern Bridger Range and didn’t see signs of instability in the new snow, but skied conservative terrain due to the rapid, heavy load (<strong><a href="https://www.youtube.com/watch?v=a8pYH4O5sNo&amp;list=PLXu5151nmAvSbcbVf…;). He is tired of talking about sugary snow at the ground, but continues to remind us it makes larger avalanches possible. Remain diligent and avoid slopes where this weak layer is suspect.</p>

<p>On Mt. Ellis weak sugary snow makes up most of the shallow snowpack (<strong><a href="https://www.youtube.com/watch?v=-iokOWUdQ3s&amp;list=PLXu5151nmAvSbcbVf… href="https://www.mtavalanche.com/images/20/snowpack-mt-ellis-shallow-and-ver…;). The northern Gallatin Range received about half as much snow as the Bridgers (9”=0.6” SWE) and in Hyalite avalanches are not as likely, but still possible. However,&nbsp;on Mt. Ellis the weak snowpack makes larger avalanches likely where new snow is drifted into thicker slabs. Today avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on other slopes.</p>

<p>Near Big Sky, West Yellowstone and Cooke City the mountains received 7-10” of snow equal to 0.4-0.8” of SWE. Avalanches are possible to trigger, especially where east wind grew fresh wind slabs. On non-wind loaded steep slopes dry loose avalanches and slabs of new snow are possible to trigger. On Thursday near Cooke City I triggered a fresh wind slab, similar to what is possible today (<u><strong><a href="https://www.mtavalanche.com/node/21803">details and media</a></strong></u>). Watch for cracking of the snow surface around your skis as a sign new snow or drifts are&nbsp;unstable.</p>

<p>A less likely, but higher consequence avalanche can break deeper and wider on sugary weak layers near the base of the snowpack (<u><strong><a href="https://www.mtavalanche.com/images/20/snowpit-crown-human-triggered-ava…;). Ian discusses this problem in his recent <strong><a href="https://www.youtube.com/watch?v=RNye2XVdYbY&amp;list=PLXu5151nmAvSbcbVf…; from Lionhead. Dave was in Cooke City over the weekend and found unstable test results on this layer, and&nbsp;his <strong><a href="https://www.youtube.com/watch?v=DYbfFxcdGnI&amp;list=PLXu5151nmAvSbcbVf…; shows the thick, heavy slab that could break. On Saturday near Big Sky a cornice fall triggered a deep avalanche (<u><strong><a href="https://www.mtavalanche.com/node/21822">details and photo</a></strong></u>), and in the southern Madison Range a snowmobiler triggered a deep and wide avalanche, and luckily was not caught (<u><strong><a href="https://www.mtavalanche.com/node/21826">details and photo</a></strong></u>).</p>

<p>Be extra cautious of wind loaded slopes, and carefully evaluate the snowpack and terrain before riding any steep slope. Avalanches are possible to trigger and the avalanche danger is rated MODERATE.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<u><strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong></u&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

Thank You, King and Queen of the Ridge Hikers!

Thanks to the 52 hikers and 9 Teams who rallied their supporters and fundraised for the event. "Strange Cattle of Map Brewing" raised the most money and Mountain Project hiked the most.

Wind Slabs on Woody Ridge

Woody Ridge
Cooke City
Code
SS-N-R1-D1.5-I
Elevation
9400
Aspect
E
Latitude
44.99370
Longitude
-109.91600
Notes

Winds Friday night transported snow creating fresh drifts that avalanched naturally over the weekend. We observed two wind slabs that released naturally on the east side of Woody Ridge both appear to be 2-3' deep and 50' wide. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
30.0 inches
Slab Width
50.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year