18-19

GNFAC Avalanche Forecast for Sat Mar 16, 2019

Snowpack and Avalanche Discussion

<p>Clear skies and warm temps yesterday affected the snow surface on most slopes. Below freezing temps overnight formed a stout melt freeze curst on all but high north facing terrain. This crust will create challenging but relatively safe riding conditions this morning. Shallow instabilities that plagued the snowpack earlier in week have gained strength and shouldn’t be a problem today (<u><strong><a href="https://www.youtube.com/watch?v=Lp1bsymrnSg&amp;list=PLXu5151nmAvRNl9ku…;). There’s still a slight chance a skier rider could trigger a pocket of wind drifted snow in high alpine terrain, but this is an isolated problem (<strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-n-madison-1">phot…;). Without a recent loading event avalanches failing near the ground are unlikely (<u><strong><a href="https://www.youtube.com/watch?v=zDZIGxGxCgY&amp;list=PLXu5151nmAvRNl9ku…;

<p>Today, the primary concern is wet loose avalanches on steep sun exposed slopes. The thick surface crust that formed overnight will hold up through the morning hours but begin to break down as the day heats up. Roller balls and point releases are signs the surface snow is becoming unstable. Move to shadier aspects or away from steep terrain if these signs of instability are present. Wet loose slides won’t be big enough to bury a skier or rider, but could push you into unfavorable terrain is you’re caught off guard (<strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-dry-loose-avalanc…;).</p>

<p>Today, dry slab avalanches are unlikely and the dry snow avalanche danger is rated <strong>LOW</strong>. The wet snow avalanche danger will start out <strong>LOW</strong> but could rise to <strong>MODERATE</strong> by this afternoon. &nbsp;</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>

Small dry loose avalanches Hyalite

Hyalite - main fork
Northern Gallatin
Code
L-ASc-R1-D1-I
Elevation
9500
Aspect
N
Latitude
45.42550
Longitude
-110.99800
Notes

From e-mail: "...today in Hyalite, we were able to get the new snow to slide easily on the older suncrust/windcrust. The new snow was very low density and not cohesive at all. However, places, where the underlying suncrust was most prevalent the snow slid easily. Generally it was just 'sluffs' or small dry/loose avalanches. Enough to knock you off your feet."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Loose-snow avalanche
Trigger
Skier
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Dry loose slides in Hyalite

Mt Blackmore
Northern Gallatin
Code
L-ASc-R1-D1-I
Elevation
9800
Aspect
E
Latitude
45.44460
Longitude
-111.00200
Notes

Dry loose avalanches were easily triggered on steep terrain in Hyalite. Six inches of recent snow easily slid on crusts buried below it, and was drifted into small wind slabs near ridgelines. These types of small slides are typically not large enough to bury a person, but are dangerous if they catch and carry you over cliffs or into trees.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Loose-snow avalanche
Trigger
Skier
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
6.0 inches
Vertical Fall
600ft
Slab Width
5.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

On Friday (3/15) dry loose avalanches were easily triggered on steep terrain in Hyalite. Six inches of recent snow easily slid on crusts buried below it, and was drifted into small wind slabs near ridgelines. These types of small slides are typically not large enough to bury a person, but are dangerous if they catch and carry you over cliffs or into trees. Photo: GNFAC

Northern Gallatin, 2019-03-15

GNFAC Avalanche Forecast for Fri Mar 15, 2019

Snowpack and Avalanche Discussion

<p>On Wednesday, the northern Gallatin Range picked up 6” of low density snow. This quick shot didn’t add a lot of weight to the snowpack, but it did create a few avalanche problems. On many slopes, the new snow rests over a sun crust that formed prior to the storm. This smooth sliding surface will allow dry loose slides to move quickly in steep terrain (<strong><a href="https://www.mtavalanche.com/images/19/dry-loose-avalanche-hyalite">phot…;). Soft slabs will also be a concern on slopes with fresh wind drifted snow. Overnight westerly winds blew upwards of 30 mph at the ridgetops. This likely formed fresh wind slabs on upper elevation slopes. Similar to the dry loose problem, wind drifts will not be exceptionally large but if triggered could be dangerous in higher consequence terrain.</p>

<p>Fresh snow will also increase the potential for wet loose avalanches as the day heats up. Watch for roller balls and small point releases on steep sun exposed slopes. Move to shadier aspects or away from steep terrain if these signs of instability are present.</p>

<p>Dry and wet snow avalanches are possible today. For this reason the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>As the days tick by without a loading event, human triggered slab avalanches are becoming less likely but remain possible in isolated areas (<strong><a href="https://www.youtube.com/watch?v=zDZIGxGxCgY&amp;list=PLXu5151nmAvRNl9ku…;). Yesterday, Ian and I rode into the southern Madison Range and found mostly strong-stable snow, but agreed wind loaded slopes near upper elevation ridgelines and steep rocky terrain will be areas to look out for (<strong><a href="https://www.youtube.com/watch?v=Lp1bsymrnSg&amp;list=PLXu5151nmAvRNl9ku…;). A slide triggered in Beehive Basin on Tuesday is a reminder of what’s possible today (<u><strong><a href="https://www.mtavalanche.com/node/20386">details and photos</a></strong></u>).</p>

<p>&nbsp;An additional problem will be wet snow avalanches on steep sun exposed slopes. This problem won’t be widespread, but something to pay attention to on south and west facing slopes during the afternoon hours. Roller balls and point releases are signs the surface snow is becoming unstable. Avoid steep slopes where these signs are present.</p>

<p>Although avalanches are unlikely, they are not impossible. Now is not the time to let your guard down and throw caution the wind. Continue to use safe backcountry protocol and always be thinking about the consequences of a slide.</p>

<p>Today, unstable snow exists on isolated terrain features, but generally safe avalanche conditions exist and the avalanche danger is rated <strong>LOW</strong>. The wet snow danger could rise to <strong>MODERATE</strong> on steep sun exposed slopes by this afternoon. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</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>