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
1/23- The main point of interest in the weather today are the strong outflow winds that are forecasted to return to our are today, and have already showed up at Thompson Pass proper with gusts to 50 MPH. There is very cold air aloft which will act to squeeze out the last bit of moisture in our area, and could create clearing skies before more moisture again becomes available tomorrow.
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` 9 F 1 F
Temp at 3000` 4 F -1 F
Chance of precip 0% 30%
(above 1000 FT) 0.00 in 0.01 in
(above 1000 FT) 0 in trace
Snow level sea level sea level
Wind 3000` ridges NE 19-42 mph NE 22-42 mph
Remarks...Wind chills will approach -40 F over the next several
Thompson Pass “DOT”
HN24W= total water received last 24 hours in inches
Our area has received 6-10 inches of snow with the latest storm (1/19-20). This new snow is sitting on a variety of wind affected surfaces, ranging from snow that is stripped down to rain crust, to pencil hard wind slab that ranges from 6 inches-3 feet deep.
There is a lot of spatial variability beneath the new snow. These variable wind 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. We may see this layer wake up if we see sufficient load, whether it be a significant snowfall, a large wind event with significant snow available for transport, or simply someone finding the sweet spot.
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.
Forecast Confidence is Moderate.
The avalanche hazard is moderate at all elevations for areas north of Thompson Pass . Human triggered avalanches are possible within the new snow up to 1 foot deep, on slopes steeper than 30°. Although unlikely, avalanches within the new snow have the potential to step down into deeper layers of the snowpack. Avoid unsupported terrain, areas that are experiencing active wind loading and terrain traps. Look for the hazard to increase if outflow winds arrive today and create new wind slabs.
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