Turkey Day-Sunday

Issued: Thu, Nov 24, 2016 at 8AM

Expires: Sun, Nov 27, 2016

As you head out on your excursion this holiday, keep yourself into tune to the quick changes that can happen to the snow surface below you. When you encounter that firm, hollow snow that no one truly likes to find, windslab, mosey back to more predictable ground.

Recent investigation on how they are bonding with the snow below was not very positive: very easy failure and propagation that could have tragic results in the right situation with steep terrain.

These slabs are scattered about the higher, wind-exposed slopes lee to ridgelines, rollovers and gullies.

Early season dangers explained here (link to summary by Avalanche Canada).

Above 2,500ft Moderate

1,800 to 2,500ft Low

Below 1,800ft None

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Wind Slab Problems:
Strong NE winds have blown bare many aspects and stacked it on on lee slopes: generally on southerly sides of terrain features. While these newish slabs seemed to be bonding fairly well (Q3 Break) with underlying snow in some places, I found a very disconcerting area of highly sensitive, poor bonding (CTV & ECTP3: Q1 SC) with the facets below. See below in snowpack for more details. Be careful out there when encountering these slabs, especially on steep slopes.

Snowpack:
The most recent couple of inches of snow has mostly blown away to the sea or was packed into more windslab on lee aspects. There are places scoured to the ground or stacked full of snow 3ft deep just above the Thompson Pass gap. Expect much more in the higher elevations.

While aspects that been being hit hard by wind were very right side up (strong at the bottom and getting softer near the surface), others aspects that protected snow from the winds had some mid-pack weaknesses of buried NSF: near surface facets.

The primary weakness is the the bond between the firm (1F+: one finger +) wind slab on top of weaker (4F: 4 finger) buried near suface facets (NSF 0.5-1mm). This interface collapsed while isolating a compression test column (CTV) multiple times and fully propagated  on the third light tap of my hand bending at my wrist (ECTP3). This was found on a south aspect above the gap on the should of Little Odyssey.

In wind protected areas, surface hoar and near surface faceting is continuing to grow interior of Thompson Pass.

Pictures:

20161123: Wind Slab on facets!!!! ECTP3 Q1 SC on 1mm NSF

20161123: Wind Slab on facets!!!! ECTP3 Q1 SC on 1mm NSF

 

20161123: At least the snow is well bonded to the ground.

20161123: At least the snow is well bonded to the ground.

 

New Tele Norm Lite

New Tele Norm Lite: Free the weight and your mind…these things shred…;)

Find more photos and observations below: at the bottom of the page. Sharing your observations helps others make informed decisions about where and how to go.

Recent Avalanche Activity

Last known activity was a snowmachine triggered windslab size 1.5 on a steep windloaded southerly slope below DOT ridge Nov.16. This problem still exists: humans, especially machines or multiple machines on the same slope, could trigger windslab big enough to injure or bury someone.

Recent Weather

The cold (7* at airport, -7* on pass, -20* at Tsaina), clear and windy (NE up to 38mph on pass) days will begin to shift as clouds start building Friday morning . By Friday evening, a flake or two may have fallen until steady precipitation starting Saturday morning could leave us with over a foot of snow by Monday night. The meat of the storm (hopefully turkey) will focus on Saturday through Sunday morning. Temperatures will rise closer to freezing in town and 20 on Thompson Pass.  Winds will shift to the SE during the storm.

Additional Info & Media

SNOW HISTORY: Valdez 11/22 AM Thompson Pass 11/23 AM
Current Snow Depth 1″ 18″
24 Hour Snow / Water Equiv. 0” /0″ 0″ / 0″
Storm Snow /Water Equiv. (11/20) 2” / 0.2” 2″ / 0.2″
November Snow / Water Equiv. 5″ / 2.87″ 37″ / 4.9″
Total Winter Snowfall / Water Equiv. ?″ / ?” 60″ / 7.3″
Snowload in Valdez 0
SNOW DEPTH & WATER SURVEY (date) Depth Snow Water Equivalent
Milepost 2.5 Valdez  ?″  ?″
Milepost 18 ?″ ?″
Milepost 29 Worthington Flats ?″ ?″
Milepost 37 Tsaina River bridge ?″ ?″
 This survey is done the first week of each month.

Weather Quicklinks:

  • NWS forecast for Northeast Prince William Sound <here>
  • NOAA NWS spot forecast for Thompson Pass <here>
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map here>.
  • Thompson Pass weather <here>.
  • Further weather resources <here>

SNOW CLIMATE ZONES:

  • Maritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  • Inter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  • Continental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).

Photo of Thompson Pass <here>

Map of Valdez Forecast areas and recreating zones <here> (Thank you Trevor Grams!)

Run map of some of the forecast area <here>

NEWS: Our region is “one of the snowiest places on earth” – Serendipity / Rendezvous snowfall record set in 1963 <here>.

Free smart phone avalanche forecasts at: http://www.avalancheforecasts.com/

Posted in VAC Forecasts.

Forecaster: Kevin Salys