Valdez
Above 4,000ftModerate
2,000 to 4,000ftModerate
Below 2,000ftLow
Degrees of Avalanche Danger
Avalanche Problems
Problem 1
Strong north winds occurred between 11/26-11/29 stripping snow surfaces down to old crusts and forming pencil hard wind slabs on lee aspects.
Time has allowed wind slabs to lock up and gain strength. It remains possible to trigger a wind slab above 2000′. A very faceted snowpack exists in the continental zone that could allow wind slabs to remain sensitive longer than what is typical.
Above 4000′ temperatures have risen to at or above freezing over the last 24 hours. This rise in temperatures creates the possibility that old wind slabs could reactivate. This is not a very likely scenario as heat will take time to penetrate into deeper layers of the snowpack, but can not be ruled out as the consequences would be high.
Likelihood:
- Almost Certain
- Very Likely
- Likely
- Possible
- Unlikely
Size:
- Historic
- Very Large
- Large
- Small
Trend
- Increasing
- Steady
- Decreasing
Problem 2
There are multiple rain crusts from October that are faceting in the mid and lower snowpack. Recent winds have created very strong snow at the surface making it difficult for a person or machine to affect these deeper layers.
There is an inversion in place (higher temperatures at upper elevation). Above freezing temperatures above 4000′ have slightly increased the likelihood for persistent slab avalanches to be triggered. This avalanche problem would probably not show signs of instability and could have significant consequences. A cold front moving in on Monday will once again lock up persistent weak layers.
There is a higher possibility of affecting these layers in the continental zone where a more faceted snowpack exists.
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
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 Sunday 12/04/22 Monday 12/05/22 Time (LT) 06 12 18 00 06 12 18 00 06 Cloud Cover SC SC FW CL FW BK OV OV OV Cloud Cover (%) 50 35 15 5 10 60 90 85 80 Temperature 20 25 25 23 22 24 26 26 24 Max/Min Temp 26 22 27 23 Wind Dir NE SW SW SW SW SW S S S Wind (mph) 2 2 2 3 4 4 6 8 4 Wind Gust (mph) Precip Prob (%) 0 0 0 0 0 10 70 70 50 Precip Type S S S S 12 Hour QPF 0.00 0.00 0.04 0.21 12 Hour Snow 0.0 0.0 0.2 2.4 Snow Level (kft) 1.6 1.5 1.3 0.6 0.3 0.2 1.2 1.2 0.9
Click on link below for Thompson Pass weather history graph:
| Date:
12/4 |
24 hr snow | HN24W* | High temp | Low temp | 72 hour SWE* | December snowfall | Seasonal snowfall | Snowpack Depth |
| Valdez | 0 | 0 | 26 | 16 | 0 | 0 | 34 | 11 |
| Thonpson pass | 0 | 0 | 24 | 6 | 0 | 1 | 98 | 30 |
| 46 mile | 0 | 0 | 13 | 3 | 0 | 1 | 1** | 16 |
*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.
Announcements
The avalanche hazard is Moderate above 2000 feet in the Continental zone. Above freezing temperatures at high elevation have been occurring for 24 hours. There is the small chance that wind slabs or persistent slabs could reactivate at upper elevations and create dangerous hard slab avalanches 2-3 feet deep. Low avalanche hazard exists below 2000 feet where old wind slabs are locked up and triggering them is unlikely.
Posted by Gareth Brown 12/4 8:00am.
For a description of avalanche problems, weather information, season history and more click the (+ full forecast) button. Avalanche forecasts will be issued Wednesday-Sunday.