Above 2000′ storm slabs are building with moderate to strong east winds loading specific slopes deeper. It is likely that upper elevations have received 12-24 inches of snow in the last 48 hours with an additional 8-12 possible today. This new snow is heavier than the snow beneath creating an upside down snowpack at the surface that will be susceptible to human triggers on slopes steeper than 32°. Wind loaded and convex terrain will be the most sensitive.
This new snow is putting stress on the 1/14 buried surface hoar layer (see problem 2) making the potential for human triggered avalanches 1-3 feet in depth likely. Storm slabs will have the potential to step down to deeper layers in our snowpack creating large destructive avalanches.
New snow will need time to settle and bond to the underlying snowpack. In the meantime Human triggered avalanches 1-3 feet in depth will be likely and natural avalanches will be possible.
Buried surface hoar in our upper snowpack is being put to the test by moderate to heavy snow and increasing temperatures over the last 48 hours. This layer has been reactive in stability test and natural avalanches have occurred in some areas loaded by wind prior to the current storm. As the overlying slab is growing in depth the sensitivity of this layer is increasing and the potential affected area is moving from specific to widespread. Elevated avalanche hazard exists today, human triggered avalanches are likely 1-3 feet in depth. Conservative terrain choices and caution route finding will be necessary for safe travel in avalanche terrain.
If we receive more snow than what is forecasted the hazard will be higher and a natural avalanche cycle could occur at this layer that would flush this problem out. This weak layer is unlikely to be present in the Maritime climate zone where warmer temperatures along with heavy rain below 2000′ have occurred.
Weak snow exists near the base of our snowpack in all three climate zones. The weather we are currently experiencing is putting these weak layers to the test and the likelihood of natural or human triggered avalanches has gone from unlikely to possible. It is unclear how much weight (rain or new snow) these layers can accept before failing. Realize if these layers do reach the tipping point very large avalanches would be the outcome. Significant weather that we are currently experiencing is when deep avalanches generally occur. The best mitigation technique, is avoidance of large avalanche terrain while a test of the snowpack is underway.
Rounding facets near the base of our snowpack from Cracked Ice at 4000′ on 1/11.
Below is a summary of observed Avalanche activity from the last 7 days. Avalanches that were noted earlier in the season can be viewed by clicking the link below.
If you trigger or observe a natural avalanche consider leaving a public observation.
Valdez Avalanche Activity
1/21- Several D2 natural avalanches were observed on wind loaded slopes that failed at the 1/14 BSH interface. These probably occurred on 1/19. Avalanches were observed on Hippie Ridge South aspect, RFS Northwest aspect, Cracked Ice Northwest aspect and Python (Cherry couloir) East aspect. These all appeared to be 1-2 feet deep.
1/20- Numerous large (D2) wet loose avalanches released from steep planar slopes in the Port of Valdez. These were caused by a foot or more of snow falling with temperatures rising to 40° F at sea level directly following. No step downs noted.
1/17- Numerous wet loose point release were observed on solar aspects in the Port of Valdez. Most of these originated from rocks were the suns energy permeated into dry snow and caused surface snow to become upside down. No step down slab avalanches were observed.
-Small (D1) spin drift avalanches on the lee side of Tones Temple ridge triggered a small slab at the 1/14 BSH layer.
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 Wednesday 01/25/23 Thursday 01/26/23
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover OV OV OV OV OV OV OV SC SC
Cloud Cover (%) 100 100 100 100 100 75 70 50 40
Temperature 30 31 32 28 27 28 27 22 19
Max/Min Temp 33 26 30 17
Wind Dir E SE S SW SW SW SW SW NE
Wind (mph) 21 12 11 11 13 13 10 2 3
Wind Gust (mph) 33 25 23 25
Precip Prob (%) 100 100 100 90 80 40 20 0 0
Precip Type S S S S S S S
12 Hour QPF 0.40 0.24 0.12 0.01
12 Hour Snow 3.6 2.2 1.1 0.0
Snow Level (kft) 2.4 2.4 2.2 1.4 1.0 0.8 0.4 0.1 0.1
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.
Click on the link below for a running summary of the seasons weather history.
Valdez Weather History
The avalanche hazard Is Considerable at all elevations. Human triggered avalanches are likely that could be big enough to injure, bury or kill a person. Natural avalanches are possible. Weak snow in the upper snowpack has been buried by 1-2 feet of new snow in the last 48 hours. An additional 8-12 inches of new snow is expected today that will keep the avalanche hazard elevated.
Posted by Gareth Brown 01/25 8:45 am.
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.
If you have pictures of recent natural or human triggered avalanches or notice signs of instability such as shooting cracks or collapsing, leave an observation to help improve forecast accuracy.
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