19-20

GNFAC Avalanche Forecast for Fri Apr 10, 2020

Snowpack and Avalanche Discussion

<p>A big swing in the weather means we’ll be worried about just about every type of avalanche at some point over the next three days.</p>

<p>Today will start off sunny and warm. Many slopes only lightly refroze overnight. Crusts will break down quickly this morning. If you’re sinking more than ankle deep into wet snow it is time to get off sunny slopes or out of steep terrain entirely because the conditions for wet slides are developing. These could be wet loose avalanches or more dangerously, wet slabs. A number of natural and human triggered wet slabs broke over the last few days and they are a possibility once again today (<strong><a href="https://www.mtavalanche.com/node/22698">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/node/22693">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/node/22688">details</a></strong&gt;). Cornices have also been breaking, so give them a wide berth and minimize your time beneath them (<a href="https://www.mtavalanche.com/images/20/massive-cornices-beehive"><strong…;).</p>

<p>Spring storms usually come with some degree of uncertainty and this one is no different. If the storm really delivers, expect to trigger avalanches within the new snow, especially on wind-loaded slopes where the new snow is drifted into deeper drifts. The faster the new snow falls and the more that it piles up the more dangerous conditions will become. The new snow will also add a (potentially rapid) load to the rest of the snowpack. If new snow starts to really accumulate before the wet snow in the snowpack has a chance to refreeze we may see more wet slab activity tomorrow. The new snow will also add stress to the buried weak layers that are still lurking on high elevation shady slopes and we may see avalanches on these layers as well (<a href="https://www.mtavalanche.com/images/20/buried-surface-hoar-crystal"><str…;, <a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-s-madison"><str…;, <a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-mt-ellis"><stro…;).</p>

<p>Don’t push it this weekend. Most avalanches occur during and immediately after a storm. Instability will rise as snow accumulates. You may have been wearing flip-flops yesterday, but it is still avalanche season in the mountains and you’ll need to bring your A-game if you’re headed out.</p>

<p>Please continue to send us your observations. You can fill out an observation form, email us (mtavalanche@gmail.com), leave a VM at 406-587-6984, or Instagram (#gnfacobs). We greatly appreciate your support.</p>

GNFAC Forecaster Chat

Monday, April 13, GNFAC Forecaster Chat: Spring snowpack and travel advice, Live Online w/ Uphill Pursuits @ 6-7 p.m. Link here for details and to join the discussion.

Natural and snowmobile triggered wet slabs near Lionhead

Lionhead Ridge
Lionhead Range
Code
WS-N-R2-D2
Latitude
44.71450
Longitude
-111.31800
Notes

Skiers in the Lionhead area saw 3 fresh wet s slab avalanches on 4/9/2020. One appears to have been triggered by a snowmobile, one by a falling c cornice and the third may have been triggered a wet loose avalanche from above or water running off rocks near the crown. 

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

Snowmobile triggered slide near Lionhead

Lionhead Ridge
Lionhead Range
Code
WS-AM-R3-D2-O
Aspect
NE
Latitude
44.71840
Longitude
-111.31900
Notes

From email: "On Tuesday,  April 7th my group noticed a s slab avalanche above our route back to the parking lot. The coordinates of the s slide are 44.7184217, -111.3190452. There were snowmobile tracks directly to the right (NW) of the s slide The s slide was considerably wide , more than100 yards."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet slab avalanche
Trigger
Snowmobile
R size
3
D size
2
Bed Surface
O - Old snow
Slab Thickness
24.0 inches
Vertical Fall
70ft
Slab Width
300.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year