2/6: 2 remote triggered avalanches on RFS at 1800-2000′.
Photo of 1st remote trigger listed
-Natural avalanches observed on south aspect at mile 40, ~1800′, 1-2 feet deep and ~100′ wide. SS-NL-R2-D1.5-O. These were triggered by small snow sluffs.
2/2: Numerous Small pockets of unsupported terrain released naturally in the tsaina valley below 2000′, 2′ deep.
1/27-1/30: Naturals were observed on RFS, N aspect ~6000′,
Avalanches were also observed on -40.5 mile, ~5000′ ,W aspect, 60 m crown
– 2 paths on Three Pigs, ~5000′, SE aspect, ran into the top 1/3 of aprons.
– 3 slides on Billy Mitchell ranging from 3000′-6000′, NW- N aspect. The most significant was on the upper bowl of cry babys, ~5000′, ~200 m crown, 1-2 meters deep.
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.
1/8- 15-20 inches of snow with 1.5 ” of SWE is forecasted for Thompson Pass. Winds will be moderate to strong out of the S-SW with temperatures in the upper 20’s for Thompson Pass.
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` 37 F 34 F
Temp at 3000` 25 F 27 F
Chance of precip 100% 100%
(above 1000 FT) 0.69 in 0.48 in
(above 1000 FT) 0-8 in 0-6 in
Snow level 1000 ft 500 ft
Wind 3000` ridges S 18-41 mph S 16-23 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 Jan through 1/30
Prolonged arctic temperatures in January have created a weak snowpack. Weaknesses in our snowpack are pronounced at old rain crusts where moisture was once concentrated, and has now formed facets. These rain crusts exist up to 3000′. Near surface facets were also formed in January and are spatially variable depending on their exposure to previous wind events.
Poor stability exists below 2500′ in the Thompson Pass region. Near surface facets up to 2 mm exists that are now buried under 2-3 feet of snow. This layer is especially prominent in areas that were protected from strong wind in January and north of Thompson pass where temperatures were colder.
Stability improves as you go up and becomes good above 3000′. Strong outflow wind events in January did not allow near surface facets to be preserved. A very strong layer of wind affected snow exists under 2-3 feet of snow that fell beginning on the 26th of January. This wind affected snow is creating a bridging effect above a faceted mid and lower snowpack. In alpine areas that were protected from January wind events persistent weak layers will be present in the upper snowpack that could still be reactive.
There is a high degree of spatial variability in our area. Careful snowpack assessment will necessary slope by slope. If you find good stability in one area don’t assume that the next place you go will be the same.
Forecast Confidence is Moderate.
Resolution is Moderate
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. If you would rather not post an observation publicly, feel free to send me an email at [email protected]
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.
The avalanche hazard is considerable at all elevations. 15-20 inches of snow is forecasted for Thompson Pass through Sunday. Human triggered avalanches will be likely and natural avalanches are possible. Warm temperatures and heavy snowfall will create a reactive upper snowpack that will need time to adjust to its new load. Avoid large avalanche paths, terrain traps, areas that are receiving active wind loading and steep low elevation terrain with consequences.
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