Continued moderate snowfall have been steadily building storm slabs since 11/25. Our thin “weak” snowpack will slowly adjust to this added weight. Natural and human triggered storm slab avalanches will be possible on 11/28, and will become likely with additional accumulation and/or increased rates of precipitation.
Winds have been blowing from multiple directions since the last round of storms began 11/25. With abundant dry snow available for transport, and changing wind direction expect wind slabs to have formed on a variety of aspects. Avoid slopes that are actively, or have recently been loaded by wind. Signs of recently loaded slopes include: new snow that gets rapidly deeper over a short distance, like over a ridge or pass. Pillowed snow surfaces, shooting cracks and freshly formed cornices.
Many Cornices are in their infancy stages of forming at this point in the season. While traveling on or below cornices is always dangerous and never recommended. They can be especially dangerous early season when they may be made primarily of freshly drifted snow that almost surely can’t support the weight of a person or snowmachine.
The Thompson Pass RWIS wind station has been down for more than 48 hours, and the FAA camera wind station has been reporting suspect data. With limited field observations during this last round of storms and the TP weather station not recording. There is a lot of uncertainty with this avalanche problem and its distribution.
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
11/28- Accumulating snowfall is forecasted to continue on Thompson Pass through Sunday, before a brief break on Monday. Warm air is forecasted to move in on Tuesday 12/1 along with another storm, which will likely switch precipitation from snow to rain in low lying areas. Updates to freezing line with this storm will happen as the event gets closer…
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` 33 F 28 F
Temp at 3000` 24 F 28 F
Chance of precip 90% 90%
(above 1000 FT) 0.26 in 0.35 in
(above 1000 FT) 1-4 in 3-5 in
Snow level sea level sea level
Wind 3000` ridges E 5-20 mph E 5-15 mph
Remarks...Nearly continuous snow expected through Thompson Pass
this weekend. The heaviest snow is expected Sunday.
Thompson Pass weather history 20/21. Click on links below the images to see full size view
TP NOV as of 11/18
Regular avalanche forecasts will begin early December. Just because we haven’t posted a hazard rating, doesn’t mean there is no hazard.
Snow and wind have been fairly consistent since 11/25, besides a brief clearing on Thanksgiving. In the last 72 hours Valdez has received 1.3″ of SWE (snow water equivalent), Thompson Pass data has not been available and 46 mile received 1″ of SWE. Our thin snowpack is weak and will have a hard time adjusting to this new load in the short term, especially in areas that have received recent wind loading.
Human triggered and Natural avalanches will become increasingly likely as precipitation continues or if temperatures warm up enough to bring rain to higher elevations.
It is easy to be excited with all the new snow, and you may want to get out there ASAP. Use caution if you venture out, this is a major transition period for our snowpack, areas of unstable snow are likely to exist during this transition. Look for signs of unstable snow and stick with conservative terrain if any of these exist. Signs of instability include: Natural avalanches observed, shooting cracks, collapsing, recent wind loading, more than 8″ of snow in 24 hours, rain on snow/rapid warming.
For more information click the (+full forecast) button below.
Your observations are valuable! If you have been out recreating in the mountains leave an observation.
Forgot your password?
Lost your password? Please enter your email address. You will receive mail with link to set new password.
Back to login
Enter the destination URL
Or link to existing content