Continued snowfall has been steadily building storm slabs since 11/25, with Thompson Pass receiving over 4 feet of snow combined with moderate wind. Rising temperatures and significant additional snow/rain will cause the upper section of the snowpack to become top heavy (upside down). This will make human triggered storm slabs up to 3+ feet deep very likely on slopes steeper than 35°. Natural avalanches in the upper snowpack are likely late 12/1 through early 12/2.
Weak Basal facets exist at the ground which have shown propagation energy in stability tests. These layers may be overcome by the 2.5″ of SWE and rising temperatures that are forecasted 12/1. Full depth natural avalanches will be possible late 12/1 through early 12/2.
11/15: Natural avalanche observed in Loveland Basin on a South aspect, down the ridge from Tones Temple. This slide was triggered by recent NE wind loading and failed at the ground. SS-N-R1-D2-G
11/16: Natural avalanche observed on Billy Mitchell “Cry babys shoulder”. Released from~3500′ with a crown length of ~200 meters, North aspect. This slide was triggered by recent NE wind cross loading the slope. SS-N-R2-D2-U
11/29: Natural avalanche observed on Billy Mitchell Cry babys shoulder, similar elevation as 11/16 slide but originated a couple hundred meters further west. Released from ~4000′ with a crown length of ~ 200 meters, North aspect, ~ 37°, failed at the ground. HS-N-R2-D2.5-G
11/30- Natural avalanche observed on 40.5 mile peak just to the South of the Shovel. West aspect, ~4500′, crown ~200′ wide, poor light prevented further observation. SS-N-R1-D2-U.
12/1- A large low pressure system will continue to affect our area through 12/2. Temperatures are forecasted to rise and bring the freezing line up to 3000′ by late Tuesday before dropping back down to sea level Wednesday afternoon. An impressive 2.5 ” of SWE are forecasted for the next 24 hours.
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` 38 F 36 F
Temp at 3000` 33 F 35 F
Chance of precip 100% 100%
(above 1000 FT) 1.06 in 1.41 in
(above 1000 FT) 0-3 in 0 in
Snow level 1900 ft 2800 ft
Wind 3000` ridges SE 5-30 mph SE 5-25 mph
Remarks...Warming temperatures, rising snow levels, heavy rain
and snow occurring through tonight. Snow levels return to sea
level by Wednesday night.
Thompson Pass weather history 20/21. Click on links below the images to see full size view
TP NOV as of 11/18
The avalanche hazard is HIGH. Avoid travel in or below avalanche terrain today. 2.5″ of snow water equivalent along with rising temperatures and strong winds will create widespread areas of unstable snow. Natural avalanches are likely late 12/1 through early 12/2.
For more information click the (+full forecast) button below.
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