Wednesday-New Year’s Eve 2017

Issued: Wed, Dec 28, 2016 at 8AM

Expires: Sat, Dec 31, 2016

Plan for visibility to be in and out today. Avoid steep rocky areas that have previously windloaded.

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

DANGER SCALE

WIND SLAB:
Elevation: 1800′ and above
Aspect: All aspects due to variable wind direction
Terrain: Near ridges, rollovers and loaded features
Sensitivity: Stubborn
Distribution: Specific
Likelihood (Human Triggered): Possible
Size: Small to Medium
Danger Trend: Decreasing
Forecaster Confidence: Fair

PERSISTENT SLAB:
Elevation: Mostly above 2500′
Aspect: All
Terrain: Steep rocky slopes where facets exist under old windslab, especially interior of Thompson Pass
Sensitivity: Stubborn
Distribution: Specific
Likelihood (Human Triggered): Possible
Size: Medium
Danger Trend: Decreasing
Forecaster Confidence: Poor

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: The most likely places for humans to trigger avalanches are windloaded gully walls and unsupported, steep rocky slopes. With a little more than two feet average snow depth at 2500′, our snowpack is still relatively thin in places with the depth and structure quite variable due to outflow wind events. In Nick’s Happy Valley, the new weather station relatively protected from wind, is reporting a snow depth of 52″.

Warmer temperatures on the coastal side of Thompson Pass has built a more uniform snowpack capped by a surface crust below ~3000′.

Above 3000′ and interior of the Pass has stayed cooler; preserving early season facets at the ground and between layers of windslab. It is not out of the picture for heavy loads such as a snowmachine or mulitple machines to trigger a steep, windloaded north facing slope and have it step down to persistent weak layers, increasing the avalanche size and destructive potential.

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

Recent Avalanche Activity

  • No new avalanches reported in the last two days.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  5 / 25
Ridgetop Wind Forecast (mph): SE / 1-15
Snowfall (in):  1-3
WIND & TEMPERATURE
past 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 5 / NNE 13 / NE
Max Wind Gust (mph) / Direction 10/ NNW 26 / NE
Temperature Min / Max (*F) 25 / 32 10 / 16

Weather Forecast: No significant precip for the last two days. Expect partly cloudy skies. Scattered flurries possible with little accumulation. Cooling trend. Light variable wind with northerly outflows picking up Wednesday.

Additional Info & Media

SNOW HISTORY: Valdez 12/28 AM Thompson Pass 12/28 AM
24 Hour Snow / Water Equiv. 1.2” /0.09” 1″ /0.05″
Storm Snow /Water Equiv. (12/28) 1.2” /0.09″ 8″ /0.7″
Current Snow Depth 27″ 27″
December Snow / Water Equiv. 68.5″ /3.8″ 53″ / 4.5″
Total Winter Snowfall / Water Equiv. 90.9″ / 7.84” 125″ / 12.8″
Snowload in Valdez 21 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.

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