18-19

GNFAC Avalanche Forecast for Thu Jan 31, 2019

Snowpack and Avalanche Discussion

<p>This is our third day in a row without snow. No snow means no loading and the snowpack is less sensitive to triggering. With a decreasing avalanche danger the odds of making a mistake in the backcountry, unfortunately, do not decrease along with it. On Saturday, many slopes were ripe to avalanche and did (<strong><a href="https://www.mtavalanche.com/avalanche-activity">full list</a></strong>). Today their numbers are much less, but knowing which slopes are still dangerous is critical.</p>

<p>On many slopes there is weak snow in the lower third to half of the snowpack. In almost all our videos over the last 2 months we show this sugary, unsupportable snow. It was responsible for the fatality in the Tobacco Root Mountains (<strong><a href="https://www.youtube.com/watch?index=2&amp;list=PLXu5151nmAvRNl9kuY3DxfW…; <a href="https://www.mtavalanche.com/accident/19/01/29">report</a></strong&gt;), and Ian triggered an avalanche on this weak layer in Taylor Fork (<u><strong><a href="https://www.youtube.com/watch?v=hh3eSrv6fYI">video</a></strong></u&gt;, <u><strong><a href="https://www.mtavalanche.com/images/19/sunlight-basin-avalanche-2">photo…;). You don’t need a Level 1 certification or snow science degree to find it, just step off your skis or sled. If you sink to the ground, you found it. Signs of instability such as cracking and collapsing, which were prevalent over the weekend are less so today, and evaluating slope stability requires work.</p>

<p>Karl Birkeland skied to Mt. Ellis yesterday and his experience is instructive. He was there on Saturday and retreated lower on the mountain when he got collapses and poor stability test scores (<strong><a href="https://www.youtube.com/watch?v=zHramxEhjO8&amp;t=0s&amp;index=5&amp;li…;). Yesterday there were no collapses and cracking, but he dug 3 snowpits (yes, he’s super into it) and found instability in each one (<strong><a href="https://www.youtube.com/watch?v=Z0dOv0z4GDI&amp;list=PLXu5151nmAvRNl9ku…;). From the summit he skied his skin track back to the car avoiding avalanche terrain. Although the avalanche danger is going down throughout our area, he found conditions that were bad. What Karl did is what we all need to do: in the absence of collapsing and cracking, dig and test the snow. It’s the only way to know what’s under our feet.</p>

<p>For today, the avalanche danger is rated MODERATE since human-triggered avalanches are still possible.</p>

<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

King and Queen of the Ridge

This Saturday, February 2, at Bridger Bowl. This is the Friends of the Avalanche Center’s second biggest fundraiser of the year. Come on out and help us raise some money by hiking and skiing some laps on the ridge. Prizes, camaraderie and a good time is guaranteed.

Natural avalanches on Mt. Zimmer

Mt. Zimmer
Cooke City
Code
HS-N-R3-D2-O
Aspect Range
N-NE
Latitude
45.11720
Longitude
-109.89200
Notes

From the email: "Two slab avalanches that looked a day or two old. Both East/NE aspect off of Mount Zimmer. One was storm snow/windslab 12'18" crown that ran 300' wide, D1.5/R3 and the other was a small width deep slab in a pocket below cliffs. 4-5'crown, 50'wide, D2/R1." 

Multiple Avalanches
Number of slides
2
Number caught
0
Number buried
0
Number killed
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Slab Width
300.00ft
Slab Layer Grain Type
Wind packed
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural avalanches up Hyalite

Hyalite - main fork
Northern Gallatin
Code
SS-N-R3-D3
Latitude
45.41310
Longitude
-110.98400
Notes

Two slides, one on Alex Lowe Peak, and another in Maid of Mist Basin:

1. "Newish slide with a fresh looking debris pile. Between Alex Lowe and Peak 9806. Appeared to step down into the old snow. Looked like a D2.5-R3, natural trigger."

2/3. "Large natural avalanche on the south face of peak 10,201. Looked to be a day or two old and the crown looked to be 3-4 feet deep in places."

Multiple Avalanches
Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
3
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

A skier wrote, "Large natural avalanche on the south face of peak 10,201. Looked to be a day or two old and the crown looked to be 3-4 feet deep in places." Photo: S. Wilson

Northern Gallatin, 2019-01-30