18-19

GNFAC Avalanche Forecast for Mon Nov 19, 2018

Snowpack and Avalanche Discussion

<p>Friday’s snowstorm dropped 5-7” in the northern ranges and 2-3” in the southern areas with westerly wind (<strong><a href="https://www.mtavalanche.com/images/18/subtle-wind-ripples">photo</a></s…; <a href="https://www.mtavalanche.com/images/18/new-cornice-growth">photo</a></st…;). Since then, the only avalanche activity reported has been new snow sluffing with ski cuts (<strong><a href="https://www.mtavalanche.com/node/19073">incident</a></strong&gt;). There have been no avalanches breaking on deeper layers. Throughout our forecast area we have a hodge-podge of surface texture: surface hoar (<strong><a href="https://www.mtavalanche.com/images/18/surface-hoar-5">photo</a></strong…;), small faceted (weak) grains and crusts on sunny aspects. Given the snow surface may change a few more times we won’t know the stability ramifications until it gets buried.</p>

<p>The deepest snow is in the northern mountains and Cooke City (2-4’) which is also where most of our field observations are from. Overall stability is good; however, an occasional snowpit test shows a weak layer of facets breaking clean in the snowpack (<strong><a href="https://www.mtavalanche.com/images/18/ramp-snowpit-profile">snowpit profile</a></strong>). Treat this as a reminder to dig, test and not make assumptions about what lies under your feet. We are still forming an initial impression on snow structure and stability, and the observations and pictures sent to us are extremely valuable.</p>

<p>New this season, we added hyperlinks to the <strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a></strong> and a new Menu item &lt;<strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanches and SnowPits</a></strong>&gt; with information on avalanche activity and incidents.</p>

<p>If you get outside send us an observation via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

November 26, MSU Snow and Avalanche Workshop, 5-9pm at MSU SUB Ballroom A

Skier triggered wet loose in Hyalite (Mt. Bole area)

Mt. Bole
Northern Gallatin
Code
WL-ASu-I
Elevation
9500
Aspect
SE
Latitude
45.42370
Longitude
-110.99600
Notes

From an email:

Today, at around 11am, my partner preformed a ski cut on the top of a gully. The area he cut was south facing and in direct sunlight. The slough from his cut gained momentum and formed a small avalanche that went down the entire gully and apron, taking all of the previous days snow with it. The avalanche went on the old snow sun-crust, and new snow interface. We ascended from the back and found very stable results in both our pits, although they were both high and north facing. No one was caught or injured.

I had already skied down part of the slope in another gully, that was entirely shaded, and produced no snow movement.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
Bed Surface
I - Interface between new and old snow
Problem Type
Loose Wet
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

GNFAC Avalanche Forecast for Sat Nov 17, 2018

Snowpack and Avalanche Discussion

<p>Winter has returned and so has the increased potential for triggering avalanches. The mountains around Bozeman and Big Sky were favored by the recent storm and will be the most likely to produce unstable conditions. The mountains around West Yellowstone and Cooke City didn’t pick up as much snow, but could still produce isolated areas of instability. The most suspect slopes across the advisory area will be those with wind drifted snow (<u><strong><a href="https://www.mtavalanche.com/photos">photo</a></strong></u&gt;, <u><strong><a href="https://www.mtavalanche.com/photos">photo</a></strong></u&gt;).</p>

<p>Winds decreased overnight, but blew hard during the onset of the storm. Upper elevation slopes leeward to west-northwest winds will be likely areas to encounter fresh wind slabs. In the Bridger Range, winds shifted to the east which could produce isolated areas of wind drifted snow on the west side of the ridge. Wind slabs won’t be exceptionally large, but will be touchy to human triggers. Even small slides can have severe consequences, especially when associated with terrain traps such as gullies, trees, or rock bands. This problem can be mitigated by making conservative terrain selections and assessing the snowpack carefully.</p>

<p>Dry loose avalanches will be another problem to look out for on steep slopes. On sunny aspects, the new snow was deposited on a thin ice crust that formed prior to the storm. This crust will make a smooth surface for the new slide. These slides won’t entrain a large&nbsp;volume of snow, but could pack enough punch to knock you over or push you into unfavorable terrain. Fortunately, avalanche activity will stay confined to new and wind-blown snow as the underlying snowpack is generally stable (<u><strong><a href="https://www.youtube.com/watch?v=ixeUg5j4s8Q&amp;list=PLXu5151nmAvRNl9ku…;). &nbsp;&nbsp;&nbsp;</p>

<p>Check out new hyperlinks to the <u><strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a></strong></u> and a new Menu item &lt;<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanches and SnowPits</a></strong></u>&gt; with information on avalanche activity and incidents.</p>

<p>If you get outside send us an observation via our website, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

November 26, MSU Snow and Avalanche Workshop, 5-9pm at MSU SUB Ballroom A