23-24

Thin Wind Slab at the Throne

The Throne
Bridger Range
Code
HS-N-R1-D1
Elevation
7800
Aspect
E
Latitude
45.88220
Longitude
-110.95200
Notes

On 12/28 we saw a recent avalanche low on the east face of the Thone. It appeared to have broken naturally during the strong downhill wind event in the Bridger Range on Monday (12/25). A 6-8" deep wind slab broke over facets approximately 100 ft wide and ran 100 vertical feet. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Wind-Drifted Snow
Slab Thickness
8.0 inches
Vertical Fall
100ft
Slab Width
100.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Thin and weak at the Throne

Date
Activity
Skiing
Snowmobiling

Snowcover on the road is significantly worse than our last visit 10 days ago. Many bare patches on the way in and more by the time we were heading out. Overheated the sleds many times. Would recommend avoiding until it snows again. Parked at the motorized boundary and climbed and descended the east face.

There was a recent avalanche low on the east face. It appeared to have broken naturally during the downhill wind event on Monday. A 6-8" deep wind slab broke over facets approximately 100 ft wide and ran 100 vertical feet. 

Climbed above the slide and dug a bit higher on of the east face (8000 ft). The slab had broken down a bit over the last week and would no longer propagate in an Extended Column Test (ECTN14 beneath the highest melt-freeze crust and ECTX on the facets lower down). 

Areas that still have a substantial slab over the ubiquitous weak layers are of the most concern. Look and feel for this cohesive slab before committing to steep terrain. 

Region
Bridger Range
Location (from list)
The Throne
Observer Name
Ian Hoyer

GNFAC Avalanche Forecast for Thu Dec 28, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Cloud cover will hinder avalanche activity from the warm temperatures. However, if the sun comes out, small and loose wet snow slides, roller balls and pinwheels will appear, but won’t pose a danger.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The overarching concern is weak snow plaguing our forecast area. Grains of unbonded sugary snow, aka. facets and depth hoar, can avalanche on slopes capped with a wind drift. Yesterday, after Ian and I put up the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/stations/taylor-fork"><span><span><… Fork weather station</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span>, </span></span></strong></span></span></span><span><span><span><span><span><span>we dug a snowpit and found layers of weak facets and talked about how a stiff wind slab would make unstable conditions (</span></span></span></span></span></span><a href="https://youtu.be/YSYlarbuzJQ"><span><span><span><strong><span><u><span>…;). In Island Park, a rider tested that theory when he got a slope to crack and move a couple inches, but not avalanche.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Signs of instability are decreasing, but the occasional report reminds us that all is not well. It remains possible to trigger avalanches. Many slopes are stable, but some are not. Weak snow blankets our forecast area and recent wind-loading at mid-mountain and ridgetops will create instability. Pay attention to changing surface conditions, back off if you get collapsing or cracking, and do a stability test before entering avalanche terrain.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>For today, the avalanche danger is rated MODERATE on all slopes in our forecast area.&nbsp;</span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

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

Cracking in IP

Centennials - Idaho
Island Park
Code
Latitude
44.51680
Longitude
-111.63000
Notes

A sledder on an east-facing slope got a slope to crack and move a couple inches, but not avalanche.

Number of slides
0
Number caught
0
Number buried
0
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year