20-21

S. Fork Deep Creek, N Facing, ~7,000 ft.

Date
Activity
Skiing

Travelled to the ridge between S fork Deep Creek and Pine Creek drainages, mostly on N to NE facing terrain between 7-9k feet. Observed numerous pockets of shallow (<5 inch) reactive wind slabs on the skin up, but these were relegated to small features and subtle crossloaded pockets. No recent natural avalanche activity seen.

Region
Out of Advisory Area
Location (from list)
Other place
Observer Name
Tim Benson

GNFAC Avalanche Forecast for Mon Apr 19, 2021

Snowpack and Avalanche Discussion

<p>New snow creates avalanche hazards for the next few days. Potentially dangerous avalanche conditions exist where the mountains received more snow, especially on slopes where east wind drifted the snow into thicker slabs that a person could trigger. When skies clear and temperatures warm tomorrow or Wednesday, expect wet loose avalanches which could be large and harmful where more new snow fell.</p>

<p>Carefully and continuously evaluate the stability of the new snow. Be extra cautious of wind-loaded slopes and watch out for drifts in less common locations due to the east and north winds. Anticipate stability to change through the day and between different aspects and elevations. Spring weather is highly variable which creates highly variable stability. Don’t let your guard down, and continue to be diligent with safe travel practices. Carry proper, functional avalanche rescue gear and only expose one person at a time to avalanche terrain.</p>

<p>Avalanches breaking deeper than the new snow are unlikely, but not completely ruled out for the season. Over the past weekend, students in an avalanche class near Big Sky found the weak, sugary snow at the base of the snowpack still exists on cold, shady slopes (<strong><a href="https://www.mtavalanche.com/images/21/depth-hoar-n-madison">photo</a></…;). Keep this weak layer in mind for the possibility of deeper wet slabs if there are extended above freezing temperatures, or the small chance dry slabs could break on this layer on cold, shady slopes. Our&nbsp;<strong><a href="https://www.youtube.com/watch?v=1PFmB3aoeNI&amp;list=PLXu5151nmAvQDzKmH… snowpack summary video</a></strong> highlights this&nbsp;poor snowpack structure. See below for additional general spring snowpack and travel advice.</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 information 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>

Announcements, Avalanche Education and Events

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.

From obs (4/18/21): "...class split and dug three pits, one on NE, one on N, and one on NW at 7623'. HS averaged around 70 - 100 cms... The NE and NW facing pits showed rounding depth hoar and no sudden CT results. None of the ECTs fractured or propagated. The N facing slope still had preserved advanced depth hoar 3 mm in size (see image)..." Photo: J. Quinn


Forecast link: GNFAC Avalanche Forecast for Fri Apr 23, 2021GNFAC Avalanche Forecast for Mon Apr 26, 2021
Northern Madison, 2021-04-18
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    • From obs (4/18/21): "...class split and dug three pits, one on NE, one on N, and one on NW at 7623'. HS averaged around 70 - 100 cms... The NE and NW facing pits showed rounding depth hoar and no sudden CT results. None of the ECTs fractured or propagated. The N facing slope still had preserved advanced depth hoar 3 mm in size (see image)..." Photo: J. Quinn


    Forecast link: GNFAC Avalanche Forecast for Mon Apr 19, 2021
    Northern Madison, 2021-04-18
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    • Lone Peak Lookout off of Jack Creek Rd

    Date
    Activity
    Skiing

    The AERIE Med AAA Level 1 avalanche course students went out for a second set of observations, aiming for northerly aspects. The class split and dug three pits, one on NE, one on N, and one on NW at 7623'.

    HS averaged around 70 - 100 cms
    Temp at 10 AM was 27 F in the shade

    The NE and NW facing pits showed rounding depth hoar and no sudden CT results. None of the ECTs fractured or propagated.

    The N facing slope still had preserved advanced depth hoar 3 mm in size (see image). The group got several Q1 CT results down near the ground but not and an ECTN on the same layer, but no progation. The north facing aspects appeared to be the best snow to ski, since there were still several stout M/F crusts on the NE and NW aspects. Staying in low angle, sheltered terrain at this evelvation seems a safe call, not sure what is going on higher up.

    Region
    Northern Madison
    Observer Name
    Jane Quinn

    Outside Jack Creek Presere

    Date
    Activity
    Skiing

    West Aspect, 7509 Elevation, 17 degree slope, HS = 80, Sky = overcast, precip S-1, Winds calm Temps= 32 F

    Our AERIE Med AAA Level 1 avalanche course took a tour through some meadows off of Jack Creek road to assess the snowpack. We found some various layers, notable a couple inches of fresh snow and groupel on top, a stout 10 cm, melt/freeze crust down 5 cm from surface, and 20 cm of rounding depth hoar at the base of the snowpack. The following is a summary of our stability tests.

    CT11 SP down 75cm, on rounding depth hoar
    CT23 SP " " "
    CT13 SP " " "
    ECTP24 down 75

    Region
    Northern Madison
    Observer Name
    Jane Quinn

    Ross Peak, Banana Couloir

    Date

    This morning we toured up Ross Peak to check out the Banana Couloir. Ascending up the East face, we noticed that recent snow was much less consolidated than what we observed on Flathead Pass and the wind slab much less cohesive. A western wind was scouring the eastern slopes near the top of the ridge, leaving nothing crust near the summit. The descent alternated between sun crust and wind buff. Without significant sun today, the snow remained cool and no increase in instability was noted. Photo shows rime deposition on trees by a humid west wind, with Ross Pass as the backdrop.

    Region
    Bridger Range
    Location (from list)
    Ross Peak
    Observer Name
    Erich Schreier
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