20-21

GNFAC Avalanche Forecast for Sun Apr 11, 2021

Snowpack and Avalanche Discussion

<p>In the northern Gallatin Range, 5” of new snow equal to 0.5” of snow water equivalent (SWE) creates heightened avalanche conditions. Last night and this morning, moderate west-northwest wind formed fresh drifts that are possible to trigger. The new snow fell on hard melt-freeze crusts which will help wind slabs and loose snow avalanches slide farther and wider. Avalanches breaking deeper than the new snow are unlikely. Before you ride steep slopes carefully evaluate the stability of the new snow, and be extra cautious of wind-loaded slopes. Watch for cracking around your skis or feet on lower angle slopes as a sign the new snow can slide on steeper slopes. Avalanches are possible to trigger and the avalanche danger is MODERATE.</p>

<p>Near Big Sky, the Bridger Range, West Yellowstone and Cooke City the snowpack is generally stable, and avalanches are unlikely aside from small, isolated slabs of wind-drifted snow. In the Bridgers and near Big Sky 2-4” of new snow equal to 0.1-0.2” of snow water equivalent (SWE) was drifted by northwest wind into fresh slabs. Though small, these slabs are potentially hazardous in higher consequence terrain like above cliffs, rocks, trees or on firm, steep slopes. If there is any mid-day sun that makes the new snow moist, small loose snow avalanches will become possible. Prior to last night’s snow, two days of moderate-strong southwest winds formed small wind slabs along ridgelines that have become difficult to trigger. Evaluate the consequences of being caught in even a small slide before riding steep terrain. Today, the snowpack is generally stable and the avalanche danger is LOW.</p>

<p>We will issue spring snowpack and weather updates each Monday and Friday through April, or as needed, and we will share relevant avalanche and snowpack observations on our website and social media. 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>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Avalanche Education, Events and Announcements

Bridger Bowl is closed, and backcountry conditions exist (video). There is no avalanche mitigation or ski patrol rescue. Please stay clear of work areas, snowmobiles, chair lifts and other equipment.

See our education calendar for an up-to-date list of all local classes.

Fairy Lake

Date
Activity
Skiing

Started early, into the alpine by 0830, the wind was already ~20-30G40, with cold windblown drifts on most aspects, but predominately E and NE slopes. I skied a SE slope, refrozen snow that never even started to warm up. By 8500ft (0945-1000), the wind was 40-50G60+, making it hard to travel because of it. It was transporting a ton of snow, but I never ran into any concerning slabs on the slope I booted/skied until the last 100ft of the coulior where I transitioned and skied down. On the egress, I skied a steepish slope, ESE at treeline that had 20-30cm of soft wind slab on the old snow. It was unreactive while skiing but definitely felt like it could slide on a steeper/less supported slope.

Region
Bridger Range
Location (from list)
Fairy Lake
Observer Name
Wyatt Gober

GNFAC Avalanche Forecast for Sat Apr 10, 2021

Snowpack and Avalanche Discussion

<p>The snowpack is generally stable, and avalanches deeper than recent snow are unlikely. On Thursday night the mountains got 3-6” of snow near Big Sky, West Yellowstone and Hyalite with 1-2” near Cooke City and the Bridger Range. This snow created small avalanche hazards that can be harmful, especially in higher consequence terrain like above cliffs, rocks, trees or on firm, steep slopes.</p>

<p>Yesterday skiers in the Absarokas saw fresh wind slabs that broke naturally on north and east aspects (<strong><a href="https://www.mtavalanche.com/images/21/natural-wind-slab-absaroka">photo…;). Drifts that formed yesterday will be more difficult to trigger today, but a few fresh drifts will grow with increasing west winds.</p>

<p>As temperatures warm through the day, or if there is rain this afternoon, shallow wet loose slides could be triggered. A few might initiate naturally near warm, rocky outcrops on slopes that receive direct sunshine, but wind and increasing cloud cover will keep wet slide activity minimal.</p>

<p>Before you ride or travel below steep slopes watch for signs of recently drifted snow or the snow surface getting wet. Signs of wind-loading include changes in snow texture, round pillows of snow, slopes directly below cornices and snow blowing off ridgelines. Signs that the snow is becoming wet and unstable include natural rollerballs or pinwheels of snow, or feeling that the snow surface has become moist and recent crusts have melted.</p>

<p>Today the snowpack is generally stable aside from small and isolated hazards, and the avalanche danger is LOW.</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>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

See our education calendar for an up-to-date list of all local classes.

Natural wind slabs in Absaroka

Other place
Out of Advisory Area
Code
SS-N-R1-D1
Aspect
NE
Latitude
45.49590
Longitude
-110.44900
Notes

From obs 4/9/21: "we saw widespread natural wind slabs on N-NE eastern slopes in the Northern Absarokas (photo)...."

Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Wind-Drifted Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

From obs 4/9/21: "...we saw widespread natural wind slabs on N-NE eastern slopes in the Northern Absarokas (photo). Winds increased throughout the morning, and evidence of wind transport became more apparent at higher elevations. We found that on aspects unaffected by wind loading, the new snow layer was not cohesive and only saw minor sluffing." Photo: E. Schreier

Out of Advisory Area, 2021-04-10

Mt McKnight

Date
Activity
Skiing

This morning we went to go check out the new snow at the west face of Mt Mcknight. From the summit, we saw widespread natural wind slabs on N-NE eastern slopes in the Northern Absarokas (photo). Winds increased throughout the morning, and evidence of wind transport became more apparent at higher elevations. We found that on aspects unaffected by wind loading, the new snow layer was not cohesive and only saw minor sluffing.

Region
Out of Advisory Area
Location (from list)
Other place
Observer Name
Erich Schreier

GNFAC Avalanche Forecast for Fri Apr 9, 2021

Snowpack and Avalanche Discussion

<p>Wind drifts of new snow can avalanche with the weight of a skier or rider today. These slides will mostly be small, but watch out for deeper drifts where avalanches could be large enough to bury someone. Pay close attention to the texture of the surface snow. If you find cohesive, stiff, windblown snow, check to see how deep the drift is and how well bonded that drift is to the old snow surface before getting onto steep slopes.</p>

<p>As the strong spring sun hits the new snow, it will rapidly lose cohesion and you will be able to trigger wet loose avalanches. These slides will be confined to the new snow, but may run long distances on hard crusts. Rollerballs and pinwheels are signs that wet loose avalanches are imminent. Wet loose avalanches will be the largest and most problematic on slopes where the new snow is deepest. Even small avalanches could push you off cliffs or into trees and slides may gain a surprising amount of volume as the new snow gets wet for the first time.</p>

<p>The avalanche danger today is MODERATE today in Gallatin Range, Madison Range, and Lionhead area.</p>

<p>&nbsp;</p>

<p>With only a dusting of new snow in the Bridger Range and near Cooke City, large avalanches are unlikely.&nbsp; The same concerns exist as in the rest of the advisory area, but less new snow means any avalanche you do trigger will be smaller. Consider the consequences of even a small windslab or wet loose avalanche if you’re planning to ride in very steep or extreme terrain. If you do find a deeper drift or more new snow than expected, a larger avalanche could break. Tone down your terrain choices accordingly.&nbsp;</p>

<p>The snowpack is mostly stable and the avalanche danger is LOW.</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>

<p>&nbsp;</p>

Upcoming Avalanche Education and Events

See our education calendar for an up-to-date list of all local classes.