Monday – Thursday

Issued: Mon, Dec 19, 2016 at 8AM

Expires: Thu, Dec 22, 2016

Choose conservative routes. Windloading near ridgelines is adding stress to persistent weak layers in upper start zones.

Above 2,500ft Considerable

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

MONDAY TUESDAY WEDNESDAY&THURSDAY
3-considerable 3-considerable

DANGER SCALE

STORM SNOW:

Elevation: Above 2000′ elevation
Aspect: All
Terrain: Primarily steeper than 35 degrees
Sensitivity: Responsive
Distribution: Widespread
Likelihood (Human Triggered): Likely
Size: Small to Medium
Danger Trend: Steady
Forecaster Confidence: Fair

PERSISTENT SLAB:

Elevation: Mostly above 2500′
Aspect: All
Terrain: Steep rocky slopes where facets exist under old windslab
Sensitivity: Stubborn
Distribution: Specific
Likelihood (Human Triggered): Possible
Size: Small to Medium
Danger Trend: Steady
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 new snow is settling and wind drifted to knee deep where wind affected.

On 12/17 a deep hard slab natural avalanche was observed on the northwest aspect above the main gully of North Odyssey above Milepost 27.5, reinforcing the concern the sugar snow (facets) on the ground have the potential to release the entire season’s snowpack.

  • December 17th: Snowmachines caused cracking down to the persistent weak layer.

kyle-stormslab-crack-20161217

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

Recent Avalanche Activity

  • Signs of instability were seen and felt by riders December 18: cracking, whumphing, and collapsing throughout Thompson Pass area. Scroll down below the forecast to view observation submissions.
  • December 17th a natural avalanche was spotted in the main gully of North Odyssey that released to the ground.

 

 

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  15 / 30
Ridgetop Wind Forecast (mph): SE / 10-20
Snowfall (in):  6-10
WIND & TEMPERATURE
past 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  NE / 5 NE / 18
Max Wind Gust (mph) / Direction NE / 0 NE / 26
Temperature Min / Max (*F) 27 /36 12 / 26

Weather Forecast: 6-10 inches of snowfall possible Monday, followed with a few more inches Tuesday, tapering to a few snowflakes Wednesday and cloudy skies Thursday. Light to moderate onshore south-easterlies throughout. Temperatures in the mid-teens until dropping into single digits Thursday.

Additional Info & Media

SNOW HISTORY: Valdez 12/19 AM Thompson Pass 12/19 AM
24 Hour Snow / Water Equiv. 0” /0″ trace″ /0″
Storm Snow /Water Equiv. (12/16-18) 13.6” /1.05″ 13″ /1″
Current Snow Depth 27″ 21″
December Snow / Water Equiv. 47″ / 3.55″ 33″ / 2.5″
Total Winter Snowfall / Water Equiv. 72″ / 7.65” 105″ / 10.8″
Snowload in Valdez 16 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): 0.1
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.
Pete Carter

Forecaster: Pete Carter