The Avy Rose shows the forecasted danger by elevation and aspect.
It adds more detail about where you are likely to find the dangers mentioned in the forecast. The inner circle shows upper elevations (mountain top), the second circle is middle elevations, and the outer circle represents lower elevations.
Think of the Rose as a birds-eye view of a mountain, looking down from above. The rose allows our forecasters to visually show you which parts of the mountain they are most concerned about.
The primary hazard today is triggering an old windslab avalanche that could be up to 2 feet deep. These will exist on the lee side of high elevation ridge lines, lee side of terrain features and in cross loaded gullies. Watch for signs of instability like shooting cracks or collapsing that would point to slopes still having the ability to produce avalanches.
North winds were moderate to strong on 12/17 depending on location and are forecasted to be similar today. Wind speeds on 12/17 did not exceed what occurred on 12/16, so additional building of wind slab depth was minimal. High elevations no longer have a significant amount of snow available for transport. Yesterday wind slabs were found to be stubborn to unreactive on test slopes and ski cuts. The possibility of triggering a lingering wind slab can not yet be ruled out. The hazard for this problem is decreasing as time goes on and wind slabs stiffen and gain strength.
In areas protected from the wind the surface consists of 2-3 feet of settled storm snow from 12/11-12/15. This soft snow is overlying a variety of bed surfaces depending upon location. In low lying areas with thick brush new snow is overlying near surface facets. In exposed areas below 3500′ the bed surface is the 11/13 rain crust and above 3500 knife-pencil hard old wind affected surfaces exist beneath the new snow. The most likely place to trigger the most recent storm snow would be in a steep area that is protected from outflow winds where the new/old interface consists of near surface facets. Pole probing is an effective tool to identify these areas.
Various old rain crusts exist near the base of our snowpack with facets in between. In many places these layers are capped by pencil -knife hard wind affected surfaces making it unlikely for a person or machine to affect them at this point.
11/14- Debris from a D3 natural avalanche at snow slide gulch ended 100 vertical feet above the Lowe river.
Large avalanches (D2-2.5)also occurred in multiple other locations including Berlin Wall, Catchers Mitt, South Three Pigs and Billy Mitchell. The activity extends beyond this list, and mostly occurred during the peak of warming and precipitation on 11/13.
Multiple natural D1-1.5 avalanches were observed on multiple aspects at low elevation. No step downs noted.
12/1- 2 D2.5 natural avalanches were noted on Three Pigs (Beaver slide, Pig Leg). Pig leg ran into the top 1/3 of the fan and Beaver Slide stopped near the end of its track. These both likely occurred during the outflow wind event 11/26-11/29.
D2 natural wind slab was observed on 40.5 mile peak on a west aspect ~3000′. Crown depth range estimated 1-2 feet and 200′ long
12/9- Several D2 natural wind slab avalanches were observed on S-W aspects at mid elevation in the intermountain region. Crowns appeared to be 1-3 feet deep. Catchers Mitt and Gully 1 were among the spots affected.
12/12- Observation of natural activity was prevented by clouds and continuing snowfall on Thompson Pass and Valdez.
12/15- DOT avalanche control work produced several D2-2.5 avalanches from upper elevations of Hogsback and South Three Pigs. Step downs were noted with one slide suspected of failing at the ground.
Natural D2-2.5 avalanche activity was observed on Python Buttress north aspect, Berlin Wall northeast aspect, Averys southwest aspect and Girls mountain just above Worthington glacier southwest aspect picture below. There was also a significant amount of avalanche activity in Keystone canyon (Bridal Veil photo below) with at least 1 deep crown reported on the ice climb Gunnison. Most of the avalanches observed involved only storm snow with only a few step downs observed. Exceptions to this include DOT control work and the keystone canyon slide noted above.
Check out our updated weather tab! A collection of local weather stations are available for viewing with graphs and tabular data included.
NWS Watches and warnings
NWS Point forecast for Thompson Pass
Date Sunday 12/18/22 Monday 12/19/22
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover SC SC SC SC OV OV OV OV OV
Cloud Cover (%) 40 45 40 40 70 70 70 85 70
Temperature 0 0 -3 -9 -10 -7 -7 -7 -5
Max/Min Temp 3 -11 -2 -9
Wind Dir NE NE NE NE NE NE NE E NE
Wind (mph) 9 16 18 17 14 16 17 11 9
Wind Gust (mph) 20 35 42 46 46 43 44 34 40
Precip Prob (%) 10 10 10 10 20 20 40 50 40
Precip Type S S S S S
12 Hour QPF 0.00 0.00 0.06 0.15
12 Hour Snow 0.0 0.0 0.0 0.9
Snow Level (kft) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Click on link below for Thompson Pass weather history graph:
*HN24W- 24 hour Snow water equivalent in inches
*SWE– Snow water equivalent
**46 mile seasonal snowfall total begins December 1st.
Our snow season began with above average precipitation and temperatures. Beginning in September, snow lines generally hung around 4500′ until 10/12. At that point our area received the first snow down to sea level with 12-16 inches on the north side of Thompson Pass.
On 10/15 wet conditions continued with the freezing line rising to 5000′ or higher. As skies finally cleared on 10/22 we were left with a thin rain saturated snowpack capped by a stout rain crust up to 4500′. Above 4500′ much deeper snowpacks existed due to significant early season snowfall at upper elevations.
Dry and cold conditions along with moderate outflow winds finished out the month of October.
On 11/1 precipitation returned with 18 inches of snow and ~1″ of SWE on Thompson Pass. This new snow was initially reactive with several natural D2 avalanches reported on Thompson Pass. These slides were running on a firm bed surface consisting of old rain crusts and old wind slabs from October.
On 11/4 a strong north wind event kicked up with 65 mph+ winds on Thompson Pass. Our snowpack received significant damage as already thin snow below 4500′ was stripped down to old wind slabs, rain crusts and the ground.
Precipitation returned on 11/8 and became heavy on 11/11. Storm totals of around 50 inches were recorded at Thompson Pass DOT between 11/8-11/13. Snow lines rose to ~3000′ near the tail end of the storm with heavy rain occurring in low lying areas.
Skies cleared on 11/14 through 11/18 with a strong temperature inversion setting up. Valley temperatures north of Thompson Pass fell to 0° F with above freezing temperatures existing above 4000 feet. Valdez temps remained mild. This weather allowed for widespread surface hoar up to 1 cm to develop in low lying areas.
Precipitation returned on 11/19, with incremental snowfall on Thompson Pass and areas north. The Valdez area received rain during this period. 12 inches have been recorded at TP DOT between 11/9-11/23.
11/26-11/29- Strong outflow (N) wind event. Many areas below 3000′ were stripped to the 11/13 rain crust, destroying the 11/19 BSH layer. Widespread very hard snow surfaces were the result.
Precipitation returned to our area on 12/5, with higher accumulation amounts near the coast. As storms cleared out on 12/7, they were directly followed by another round of strong north winds. These winds once again incurred severe damage to our snow stripping surfaces back to the 11/13 rain crust on windward aspects and further building pencil hard slabs on lees.
12/11- Significant snowfall event that dropped 12-24 inches+ in a 12 hour period.
12/12-12/15- Steady snowfall continues with short breaks between pulses. Storm ended the night of 12/15 with 2+ feet accumulating overnight above 2000′. Valley locations received heavy rain. A fair number of natural avalanches occurred on all aspects and elevations. These were primarily concentrated to storm snow with very few step downs noted. DOT control work was the exception.
12/16-12/18- Another round of strong outflows directly followed the 12/11-12/15 storm cycle.
The avalanche hazard is moderate at all elevations. It remains possible to trigger an avalanche 1-2 feet deep on steep slopes previously loaded by north wind. Watch for signs of instability such as collapsing and shooting cracks that would indicate a slope has the potential to produce an avalanche.
Posted by Gareth Brown 12/17 8:00am.
For a description of current avalanche problems, weather information, season history and more click the (+ full forecast) button. Avalanche forecasts will be issued Wednesday-Sunday.
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