Snow has returned to the Valdez/ Thompson Pass region with heavier accumulations near the coast. Valdez has received _ and Thompson Pass has received 5.5 inches the last 48 hours. This new snow is falling on very hard, low friction (slick), wind damaged surfaces. Expect to find widespread instabilities near the coast where more snow fell and temperatures warmed overnight creating top heavy storm slabs. For the continental and intermountain zones instabilities will exist in specific areas. These areas include places were southerly storm winds have redistributed new snow into deeper slabs that may be reactive. Watch out for the lee side of high elevation ridge lines as well as cross loaded gullies and the lee side of terrain features.
Additional accumulation during the day Wednesday are expected to be light. During the afternoon moderate to strong north winds are expected to kick up which will add further stress to SE-NW aspects. Avoid slopes that have been previously loaded by storm wind as well as those being actively loaded by north winds.
Thin (weak) snowpacks can not handle the sudden changes that a strong (thick) midwinter snowpack can. As snow and weather conditions change expect to encounter areas of unstable snow.
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. New snow is adding stress to these layers, but at this point it is unlikely that we have received enough new snow to overcome the strong bridging affect of the wind damaged snow from late November that is near the surface. It is possible that smaller storm snow or wind slab avalanches could have enough force to step down to these deeper layers.
Affecting this avalanche problem is currently unlikely, but will likely become a problem later in the season once we begin to receive some significant snow.
There is a higher possibility of affecting these layers in the continental zone where a more faceted snowpack exists.
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
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 12/07/22 Thursday 12/08/22
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover OV OV OV OV OV OV BK BK BK
Cloud Cover (%) 100 95 95 90 75 75 60 65 65
Temperature 26 25 23 19 14 13 12 10 10
Max/Min Temp 26 14 15 7
Wind Dir E NE N N N N N NE N
Wind (mph) 8 12 29 33 31 32 28 26 16
Wind Gust (mph) 27 36 48 49 52 57 51 46 36
Precip Prob (%) 90 20 10 10 10 10 10 10 10
Precip Type S S
12 Hour QPF 0.06 0.00 0.00 0.00
12 Hour Snow 0.6 0.0 0.0 0.0
Snow Level (kft) 0.3 0.1 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.
The avalanche hazard is Considerable above 1500′ in the Maritime zone. Recent snow has elevated the avalanche hazard making human triggered avalanches likely 1-2 feet deep on slopes steeper than 32°. New snow is falling on a slick bed surface that may have trouble bonding initially. The avalanche hazard below 1500′ is Moderate due to thick brush acting as anchors in the thin low elevation snowpack.
Posted by Gareth Brown 12/7 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.
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