Thursday-Sunday

Issued: Thu, Nov 17, 2016 at 9AM

Expires: Sun, Nov 20, 2016

The snowpack is quite variable with elevation and in relation to the pass proper. Expect less powder and more crusts on the south side of the pass and deeper/softer snow the higher and more interior you travel due to colder temperatures (less rain) during the recent storms.

Be careful near ridges, rollovers and crossloaded gullies: sensitive new windslabs have been human triggered yesterday. See activity section below.

Read this summary on early season conditions posted on Avalanche Canada.

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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:
In the last couple days, consistently strong and gusty outflow winds from the northeast have been funneling through the pass and have created sensitive wind slabs on lee aspects. Snowmachiners found and triggered this problem Wednesday. Mostly southerly facing slopes are building this new problem, but make sure others aren’t susceptible by checking the winds and how they are moving and loading snow on the terrain you are immediately using. Also, due to the southerly, onshore winds with the previous storm, be wary and make sure to investigate older slabs created on opposing, northly slopes. The cold temps out there will necessitate more time for new snow to bond to old.

Snowpack:
The most recent storm ended Nov.12. It deposited 2.5 inches of water equivalent in our mountains, above 3500′, it all came as snow. Expect new snow to be 3 feet thick in the upper elevations.

A few eager snowmachiners were exploring around the flats and wind-loaded faces Wednesday, but seemed to often be punching through to vegetation. Creeks are wide open and alders not buried.

Recent explorations on Wednesday revealed about 2 feet of mostly soft snow (few thin crusts) at the highway below Nicks and only a foot at on the ground at the hairpin below Moonlight. The south side of the pass saw significantly warmer weather and rain, so therefore only has 4 inches of soft snow at the surface before one encounters a crust. See more observations below.

Over the last few days on the north side of Thompson Pass, a cloud ceiling at the pass height has developed a significant and widespread rime layer at the surface. In contrast, the snow surface on the cloud-free, south side of the pass was dominated by beautiful surface hoar up to 12mm in height. While this crystal can be gorgeous, it also can become a future problem worth noting and monitoring….help us do that by submitting what you find in the coming days!!! These guys can linger in cold, clear and calm areas at all elevations.

Please share your observations so everyone can be in tune with the conditions and make wise decisions – even just a photo or quick summary of whats going on out there helps all of us.

Pictures:

20161116: 27 Mile Conditions

20161116: 27 Mile Conditions

20161116: N Side Cloud Ceiling

20161116: N Side Cloud Ceiling & Open Creek

Recent Avalanche Activity

Wed. Nov. 16: A snow machine triggered a D1.5 soft wind slab on the southerly aspect of DOT/Loveland Ridge just above camp. The photo doesn’t help much other than with general location. Crown (just at sun/shade line) was likely 2ft thick and peeled off a fairly steep, wind loaded slope.

20161116 DOT conditions with machine triggered D1.5 on ridge to right of shed.

20161116 DOT conditions with machine triggered D1.5 on ridge to right of shed.

 

Recent Weather

Given a consistent high pressure in the interior, expect continued outflow winds from the north over the passes. It seems that clouds will build this afternoon from the south, break again tonight, then build up again Friday as a weak low over the Gulf of Alaska will push in a sprinkling of snow that could amass to a couple inches by Friday night. Skies could open slightly on Saturday with limited to no precipitation through the weekend. Temps should remain cold and below freezing in town.

Additional Info & Media

SNOW HISTORY: Valdez 11/14 AM Thompson Pass 11/15  AM
Current Snow Depth 1″ 21″
24 Hour Snow / Water Equiv. 0” /0″ 0″ / 0″
Storm Snow /Water Equiv. (11/11-12) 2” / 2.1” 17″ / 3″
November Snow / Water Equiv. 2″ / 2.75″ 35″ / 4.7″
Total Winter Snowfall / Water Equiv. ?″ / ?” 58″ / 7.1″
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.

Forecaster: Kevin Salys