Wednesday – Saturday

Issued: Wed, Dec 14, 2016 at 8AM

Expires: Sat, Dec 17, 2016

The POLAR EXPRESS has returned. Cold north outflow wind.

Be wary of windslab; the harder it is, the further it can propagate.

Above 2,500ft Moderate

1,800 to 2,500ft Low

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

WEDNESDAY THURSDAY FRIDAY & SATURDAY
2-moderate 2-moderate 2-moderate

DANGER SCALE

WIND & PERSISTENT SLAB:

Elevation: Mostly above 2500′
Aspect: All where exposed to wind, particularly south and west
Terrain: Ridgelines, rollovers, cross-loaded features
Sensitivity: Stubborn
Distribution: Specific steep features
Likelihood (Human Triggered): Possible
Size: Small to Medium
Danger Trend: Steady
Forecaster Confidence: Fair
Details: This problem remains for the foreseeable future.

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: In areas exposed to strong northerly outflow wind and channeled terrain, pockets of hard windslab are laid in over faceted snow. Depth is thin and variable due to wind distribution; bare rocks to 3 foot drifts. Surface texture is everything from smooth windboard, sastrugi and the old Nov.12 crust in wind affected areas. Faceted softer snow is found in areas protected from the wind.

Cold temperatures continue to make weak sugar snow (facets) between layers of windslab, around bushes and rocks, and at the ground.

Surface hoar was observed Tuesday. In wind protected areas, this could be buried in tact by the next storm.

Find more photos and observations at the bottom of the page. Sharing your observations helps others make informed decisions.

Recent Avalanche Activity

  • No new activity observed.
  • Dec.11  Fresh fracture line on the north aspect of Berlin Wall into Gully 2 at about 4000′, crossloaded start zone above rocky unsupported terrain. See photo on the obs page.

20161210-natural-wind-slab-to-ground-in-gully-1-vertigo

December 10 windslabs to ground at Milepost 29

20161204 North Odyssey Wind Slab Triggered by Snow Machine

20161204 MP 26 North Odyssey Wind Slab Triggered by Snow Machine & Rider

20161203 Triggered from below

20161203 MP 26 Triggered from below: Odyssey Lake

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  0/20
Ridgetop Wind Forecast (mph):  10-45/ NE
Snowfall (in):  0
WIND & TEMPERATURE
past 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 10 / NNE 26 / NE
Max Wind Gust (mph) / Direction 13 / NE 43 / NE
Temperature Min / Max (*F) 15 / 21 -7 / 3

The ridge of high pressure continues with cold temperatures and clear skies. North wind to 45mph at passes and ridgetops. We might see a few flurries Thursday evening as a new storm approaches. By weekend temps will warm, possibly above freezing.

Additional Info & Media

SNOW HISTORY: Valdez 12/14 AM Thompson Pass 12/14 AM
24 Hour Snow / Water Equiv.  0” /0″ 0″ /0″
Storm Snow /Water Equiv. (12/8-12/9) 10” /0.6″ 3″ /0.2″
Current Snow Depth 18″ 18″
December Snow / Water Equiv. 32″ / 2.2″ 20″ / 1.5″
Total Winter Snowfall / Water Equiv. 54″ / 6.3” 92″ / 9.8″
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 32.2″ 6.4″
Milepost 37 Tsaina River bridge 24.1″ 4.1″
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 (2MB download)<here> (Thank you Sean Wisner)

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