Valdez
Above 4,000ftModerate
2,000 to 4,000ftModerate
Below 2,000ftModerate
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.
Degrees of Avalanche Danger
Avalanche Problems
Problem 1
Old wind slabs formed on 12/17 have settled, gained strength and become unreactive. Light snow began on 12/19 with 1-3 inches of accumulation while moderate north winds continued. This is forming thin windslabs on lee aspects which has caused the top few inches of snow to become upside down.
At this point this avalanche problem does not pose a significant hazard to backcountry travelers in most locations. Isolated areas may have received more snow with specific terrain features being loaded deeper. Poor terrain choices, such as skiing a steep lee slope above a terrain trap would be an instance where this avalanche problem could pose a significant hazard.
Anticipate the hazard for this avalanche problem to increase as more snow becomes available for transport and deeper slabs form. To evaluate the potential hazard of this problem, check the depth and sensitivity of fresh/forming windslabs.
Likelihood:
- Almost Certain
- Very Likely
- Likely
- Possible
- Unlikely
Size:
- Historic
- Very Large
- Large
- Small
Trend
- Increasing
- Steady
- Decreasing
Problem 2
Faceted snow near the base of the snowpack has been identified in all three forecast zones. In most locations above brush line, faceted snow is capped by pencil-knife hard wind affected snow. This has created a strong bridging affect making a person or machines weight unlikely to directly affect these layers.
Our area received 3-4 inches of snow water equivalent over a 5 day period beginning 12/11. This put significant stress on these weak layers. Natural avalanches did occur, but activity was not widespread and natural avalanches were mostly confined to the storm snow. This points to the strength of the wind hardened snow overlying the weak facets at the base of our snowpack.
It has been five days since the last significant snowfall event and stability tests that directly target these layers have not produced propagation since. One exception was an interior location just north of our continental forecast zone where propagation in stability tests still existed on 12/18.
Persistent weak layers are tricky to assess and are notorious for surprising people. As long as temperatures remain cold and our snowpack is thin, these weak layers will continue to lose strength. It is likely that facets will reactivate in the future when stress is being applied through dramatic changes in weather such as: significant snow accumulation, rapid warming and wind loading. Maintaining safe travel protocols such as skiing one at a time and avoiding traveling in or above terrain traps will increase your safety margin.
The most likely areas to trigger a persistent slab avalanche would be in steep terrain that was protected from previous strong winds that have occurred this season. This could be below brushline or in areas of terrain that are typically spared from outflows. The Continental zone remains suspect as this area has a weaker snowpack and generally receives less wind, which would decrease the bridging affect mentioned above.
Likelihood:
- Almost Certain
- Very Likely
- Likely
- Possible
- Unlikely
Size:
- Historic
- Very Large
- Large
- Small
Trend
- Increasing
- Steady
- Decreasing
Avalanche Activity
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.
Weather
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
NONE
NWS Point forecast for Thompson Pass
Date Wednesday 12/21/22 Thursday 12/22/22 Time (LT) 18 00 06 12 18 00 06 12 18 Cloud Cover OV OV OV OV OV OV SC SC FW Cloud Cover (%) 70 70 70 70 70 75 30 25 25 Temperature 1 -3 -5 -5 -2 -2 3 5 6 Min/Max Temp -8 -1 -7 6 Wind Dir NE NE NE NE NE NE NE NE N Wind (mph) 12 11 8 11 12 9 11 13 16 Wind Gust (mph) 35 34 26 31 32 Precip Prob (%) 50 40 20 30 40 20 5 0 5 Precip Type S S S S S S 12 Hour QPF 0.10 0.04 0.03 0.00 12 Hour Snow 0.0 0.0 0.0 0.0 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:
| Date:
12/21 |
24 hr snow | HN24W* | High temp | Low temp | 72 hour SWE* | December snowfall | Seasonal snowfall | Snowpack Depth |
| Valdez | 1 | .1 | 11 | 6 | .1 | 50 | 85 | 38 |
| Thompson pass | 3 | .085 | -13 | -21 | .085 | 73 | 175 | 32 |
| 46 mile | N/O | N/O | -10 | -17 | N/O | ~22 | ~29** | 27 |
*HN24W- 24 hour Snow water equivalent in inches
*SWE– Snow water equivalent
**46 mile seasonal snowfall total begins December 1st.
Additional Information
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. Temps dropped to well below 0 on Thompson Pass and north as an inversion was in place through the 17th, with temps at 5000′ in the teens. This inversion broke down on the 18th with temps below 0 at all elevations in the intermountain and continental zones.
12/19- Light snowfall returned with moderate outflow winds continuing.
Announcements
The avalanche hazard is moderate at all elevations. Light snowfall along with moderate north winds will be forming fresh wind slabs that could be triggered by a person up to 6 inches deep. The hazard will be increasing if more snow accumulates and outflow winds continue.
Posted by Gareth Brown 12/21 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.