Clouds have limited the ability to see natural avalanche activity during the latest storm.
1/23- Found fresh debris in a gully off point 3848′ behind the airport. D2, ran ~2000′.
~ 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
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` 21 F 12 F
Temp at 3000` 18 F 7-18 F
Chance of precip 90% 60%
(above 1000 FT) 0.12 in 0.02 in
(above 1000 FT) 2-3 in trace
Snow level sea level sea level
Wind 3000` ridges NE 10-25 mph NE 8-28 mph
Thompson Pass “DOT”
HN24W= total water received last 24 hours in inches
Thompson Pass weather history 19/20 season beginning 12/21 through 1/23. Click on links below to see full size image.
TP DEC 19
TP WX JAN 20
Our area has received 2 feet of new snow from storms beginning the 26th. This new snow has been redistributed by strong NE wind onto lee aspects (SE-NW) in areas exposed to wind. Beneath this new snow exists developed near surface facets up to 3mm. This layer of near surface facets is a weak layer in our upper snowpack and will have a difficult time adjusting to the weight of the new snow. This is evident by very large collapses rolling across terrain that have been experienced the last couple of days.
There is a lot of spatial variability beneath the layers mentioned above, mostly consisting of variable wind affected surfaces. These surfaces have gained a lot of strength and are creating a bridging effect above a faceted mid and lower snowpack. Poor structure exists in the mid and lower pack and although unlikely, still has the ability to create destructive avalanches. This set up is low probability, high consequence.
We have likely not seen the last effects from this faceted snow in the mid and lower snowpack. We may see this layer wake up if we see sufficient load, whether it be a significant snowfall, increase in temperatures, a large wind event with significant snow available for transport, or simply someone finding the sweet spot.
1/24 Photo of reactive test slope on a cross loaded gully, west aspect, ~2500′. See video in observations.
Near surface facets found at 3000′ on Billy Mitchell 1/19. 2 MM grid.
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 see something in the mountains that could contribute to this forecast, leave a public observation. The more observations we receive, the better we can tune our forecast.
Be aware that the elevation bands have changed on our website. Low is now below 2000′, Mid is 2000-4000′ and high is 4000′ and above.
Forecast Confidence is Moderate.
The avalanche hazard is Considerable at mid and upper elevations. We have received 2 feet of new snow this week beginning 1/26. This new snow is sitting on a fragile snowpack, which will take longer to adjust to its new load than the typical 24 hour rule. Human triggered avalanches are likely today in terrain steeper than 30°. Avoid travel in large avalanche paths and above terrain traps.
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