Monday-Thanksgiving

Issued: Mon, Nov 21, 2016 at 8AM

Expires: Thu, Nov 24, 2016

Consider the consequence of the terrain you choose. Routes that avoid windslab on slopes greater than 30 degrees will reduce your risk and increase your snow quality experience.

Windslab sounds hollow and drummy; shooting cracks are a red flag indicating the slab could be triggered from below and/or propagate quite far.

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:
Outflow wind over the last week has produced windslab 1-3 feet thick lee to fetch areas in the upper elevations. Most of the snow available for transport in wind exposed areas was moved, but now with prolonged cold temps, the wind is recycling the faceted surfaces.

Snowpack:

A few flurries yesterday amounted to a couple inches at the Pass. This covers varied surfaces and rocks. Average depth at 2500′ is about 20 inches.

Early season snow conditions mean variable depth from wind drifting: think bare/drift/bare in places. With the cold temperatures snow is losing strength through faceting (becoming drier and sugery).

Areas of surface hoar remain north of Thompson Pass where wind protected.

Pictures:

20161116: 27 Mile Conditions

20161116: 27 Mile Conditions

20161116: N Side Cloud Ceiling

20161116: N Side Cloud Ceiling & Open Creek

Find more photos and observations below. 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 a week ago. This problem still exists; humans, especially machines or multiple machines on the same slope, could trigger windslab big enough to injure or bury.

Recent Weather

While a low pressure system is stalled in the northern Gulf of Alaska, our area will continue to experience strong outflow wind. Expect cold and windy weather through Thanksgiving. Broken sky, with clearing possible. Significant windchill. No significant snow until the weekend.

Additional Info & Media

SNOW HISTORY: Valdez 11/21 AM Thompson Pass 11/21 AM
Current Snow Depth 2″ 18″
24 Hour Snow / Water Equiv. 2” /0.2″ 2″ / 0.2″
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>

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.
Sarah Carter

Forecaster: Sarah Carter