Monday – Thursday

Issued: Mon, Dec 05, 2016 at 8AM

Expires: Thu, Dec 08, 2016

Finding wind protected areas to play is the challenge today. If you choose to brave the cold, prepare for windchill well below zero fahrenheit near Thompson Pass. Avoid traveling on, underneath, or adjacent to steep windloaded slopes. Shooting cracks, collapsing, and whumphing are signs that windslab could avalanche.

Above 2,500ft Moderate

1,800 to 2,500ft Moderate

Below 1,800ft Low

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

GENERAL DANGER RATING OUTLOOK

MONDAY TUESDAY WEDNESDAY & THURSDAY
2-moderate 2-moderate 2-moderate

DANGER SCALE

WIND & PERSISTENT SLAB:

Elevation: Above 1800′ in the alpine
Aspect: All where exposed to wind, particularly south and west
Terrain: Ridgelines, rollovers, cross-loaded features
Sensitivity: Stubborn
Distribution: Specific features
Likelihood (Human Triggered): Possible
Size: Small to Medium
Danger Trend: Steady
Forecaster Confidence: Good
Details: Sustained north wind has built hard windslab over facets.

AVALANCHE PROBLEM SCALE DESCRIPTORS:

Sensitivity: Non-reactive, Stubborn, Responsive, Touchy
Distribution: Isolated, Specific, Widespread
Likelihood: Unlikely, Possible, Likely, Nearly Certain
Size: Small, Medium, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION:
One to two feet of new snow fell Nov.30-Dec.1. Since then, northerly outflow wind to 80mph across exposed terrain has redistributed the snow into hard windslab and drifts.

Steep slopes near ridgelines were naturally and human triggered Dec.2 & 3. A few of these avalanches to size 2, stepped down to an old faceted layer and facets at the ground. Both mid-pack and ground level faceted (sugar snow) layers fail in tests.

20161202 Strong Outflow Winds

20161202 Strong Outflow Winds

20161202 Outflow winds at the gap

20161202 Outflow winds at the gap

Some preliminary poking around in the maritime snowpack with the PWSC avalanche 1 class over the weekend showed 60cm/24″ in the lower elevations. In wind protected areas, the snow is soft at the top getting more dense, save for weak 1-3mm facets at the ground. Tests showed the whole pack collapsing at the ground.

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

20161203 Bald Boy & Adjacent Sympathetic?

20161203 Bald Boy & Adjacent Sympathetic

20161203 Triggered from below

20161203 Triggered from below: Odyssey Lake

  • Clear skies Friday and Saturday, December 2nd and 3rd, revealed some natural windslab avalanches:
    • North face of Odyssey: D2 cross-loaded slab release. Crown already filling back in. Ripped to rocks in a sections of the track
    • MP 33-35: North side of highway. South faces of Max High and peak to the left. Wind slab and loose dry to size D2.
    • West Peak above airport: D2 loose snow coming out of steep, rocky terrain running down a chute several hundred feet.
20161202 N Odyssey Cross Loaded Slab Release

20161202 N Odyssey Cross Loaded Slab Release

20161202 Mile Post 33 Natural Avalanches

20161202 Mile Post 33 Natural Avalanches

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F): -11/-4
Ridgetop Wind Forecast (mph):  NE/15-35
Snowfall (in): 0-1
WIND & TEMPERATURE Past 24 Hours: Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 20 / NE 35 / NE
Max Wind Gust (mph) / Direction 37 / NE 50 / NE
Temperature Min / Max (*F) 8 / 21 -10.5 / 0

Clear sky with cloud moving in tonight. Chance of flurries beginning tonight through Tuesday, no significant accumulation; dusting to 2 inches. Outflow wind continuing.

Additional Info & Media

SNOW HISTORY: Valdez 12/5 AM Thompson Pass 12/5AM
24 Hour Snow / Water Equiv.  0” /0″ 0″ /0″
Storm Snow /Water Equiv. (11/30-12/1) 19” /1.4″ 16″ /1.2″
Current Snow Depth 15″ 18″
December Snow / Water Equiv. 19″ / 1.4″ 16″ / 1.2″
Total Winter Snowfall / Water Equiv. 41″ / 5.5” 88″ / 9.5″
Snowload in Valdez 10 lbs/sq. ft.

 

SNOWFALL for LAST 24 HRS at OTHER STATIONS:
Nicks Valley at 4200 ft (in): 0
Upper Tsaina at 1750 ft (in): 0
Sugarloaf at 550 ft (in): 0
SNOW DEPTH & WATER SURVEY (12/6/2016) Depth Snow Water Equivalent
Milepost 2.5 Valdez  13.2″  2.3″
Milepost 18 15.4″ 2.1″
Milepost 29 Worthington Flats ?″ ?″
Milepost 37 Tsaina River bridge ?″ ?″
This survey is done the first week of each month beginning in December.

Weather Quicklinks:

  • NWS forecast for Northeast Prince William Sound <here>
  • NOAA NWS spot forecast for Thompson Pass <here>
  • Thompson Pass RWIS weather station <here>
  • MP 30 Nicks (Happy) Valley weather station at 4200 feet <here> (scroll to Nicks Valley)
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map 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.
Sarah Carter

Forecaster: Sarah Carter