There has been a lot of natural activity with this outflow event. Many crown have been quickly blown back in while others are being scoured and re-exposed from the 12/30 natural cycle.
Sometime around 1/10- There have been several natural windslabs that have released in the Thompson Pass region:
-South slope of catchers mitt, near 27 mile icefall,~3500′, ~300m wide ,~3′ deep, ran 500′ HS-N-R3-D2.5. Photo shows extent of crown, which may have been bigger and is now filled in by wind transported snow.
– Gully Between Little and Big Oddessey, NW, 4000′, ~60 M wide, ~2-4′ crown, ran 1000′
-Averys, ~4000′, SW, ~70 M wide, ran ~1000′
1/11- Two natural wind slab avalanches observed at moonlight basin, 2500′-2800′, S aspect.
The first was on the small last roll before the road and had debris chunks up to 3′ deep “crown filled in by wind”, 200′ wide.
The second was in a cross loaded gully ~ 300′ above the road, with a crown up to ~10′ deep, ~100′ wide.
1/7- Report of a Glide crack release on snowslide gulch at ~3000′. D2-2.5, crown depth ~ 3 meters. Release did not produce sympathetic avalanches.
Numerous D3 avalanches were observed on the east side of the road, north of Thompson Pass. Between Gully 1 and Cracked Ice, every buttress had significant avalanches originating from ~3000-3500 ‘, NW-NE aspects. Gully 1 and 2 had debris in the drainages, with Gully 2 running a considerable distance into the flats. These avalanches most likely ran between 12/29 and 12/31 during a significant spike in temperatures. There were many other naturals during this period. Many of these have been filled in by new snow and are being blowing in by the current wind event, making them hard to see.
12/31 Numerous small-medium natural avalanches observed below 4000′ on steep rollovers on the north side of the pass.
12/30 Natural avalanche observed on Cracked Ice Butress at 2700′. ~300 meters wide, 1 meter+ deep. Connected through gullies and over ridges.
D3 avalanche on east face of Mt. Tiekel (MP 50). Ran into top 1/3 of apron.
12/28- Several natural avalanches reported in the 54 mile area near brush line. 100′ wide and ran 300′. Depth was not observed.
12/26- Skier triggered avalanche on Cracked Ice Buttress: N aspect, 2500′, 37° slope, 18 inches deep, 100 feet wide, ran 200-300 feet. SS-ASu-D1-R1-I
12/24- Skier triggered avalanche on Python Buttress: NW aspect, 2700′, 35° slope, 60 feet wide, ran 200-300 feet. SS-ASu-D1.5-R1-O
1/19: A low pressure system to our south will move clouds into our area, and the chance for light snowfall through tonight. Only light accumulations are expected.
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
This forecast is for use in snow safety activities and emergency
Temp at 1000` 17 F 15 F
Temp at 3000` 18 F 18 F
Chance of precip 80% 60%
(above 1000 FT) 0.12 in 0.09 in
(above 1000 FT) 1-2 in 0-2 in
Snow level sea level sea level
Wind 3000` ridges NE 11-42 mph NE 12-36 mph
Thompson Pass “DOT”
HN24W= total water received last 24 hours in inches
The surface snow consists of a variety of wind affected surfaces, ranging from snow that is stripped down to rain crust, to pencil hard wind slab that ranges from 1-3 feet deep and deeper in spots. Wind slabs are gaining strength as snow that is available for transport is becoming exhausted, and wind speeds diminish. Current wind slabs are stubborn to triggers , but are not dead yet. Large collapses and shooting cracks are a good indicator that the snow you are traveling on still has the energy to produce avalanches. Avalanches will likely be initiated from the thin areas of a slab. Avoid large wind loaded slopes.
We have a problem layer below 4000′ that is now buried deep within the snowpack. This poses multiple problems that may make decision making difficult. Since this layer is buried deeply, it may not show the normal signs of instability- shooting cracks, collapsing. Also, it may allow multiple people to ski or snowmachine on a slope before someone finally finds the sweet spot and triggers an avalanche. This type of avalanche will be most likely triggered from areas where the slab is thinner and the weak layer is closer to the surface, near rock outcroppings, or other thin areas of the snowpack. With the snow surface changing to hard wind board, this layer will become less likely to affect. This problem is more significant the further north you go from Thompson Pass.
ECT– Extended Column Test
PWL– Persistent Weak Layer
PST– Propogation Saw Test
HS- Height of snowpack
The new snow has opened up different access points. Use caution as you step forward into new zones. New snow combined with strong winds from different directions has created a lot of spatial variability in our area. Use terrain progression as you step out into new zones. Test smaller slopes before you step out onto larger ones.
There have been limited observations from interior locations due to low snow at lower elevations. Use caution if you travel in these areas.
If you have traveled in the mountains, please leave a public observation. The more info we can get from various locations will help us to get a clearer picture of the snowpack in our beautiful Valdez Chugach!
Forecast Confidence is Moderate.
The avalanche hazard is Moderate at mid and upper elevations. Human triggered avalanches are still possible on recently wind loaded slopes. Wind slab often has a hollow drum like feel. Collapsing, shooting cracks and active wind loading are all signs that a slope still has the energy to produce an avalanche. Avoid unsupported terrain, areas that are experiencing active wind loading and terrain traps.
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