Saturday-Tuesday

Issued: Sat, Dec 03, 2016 at 8AM

Expires: Tue, Dec 06, 2016

Once again, strong, outflow, post-storm winds have redistributed, compacted or completely blown away our fresh snow. This will leave us again with a variety of surface layers that will make for challenging recreation.

Sensitive wind slabs will continue to form and possibly release naturally.

Choose lower angle, benign terrain to assess the conditions before going steeper.

While in the snow, make sure deeper, weak facets (sugar snow) are not problematic where you are exploring.

It still is early season: Early season dangers explained here (link to summary by Avalanche Canada).

Above 2,500ft Considerable

1,800 to 2,500ft Considerable

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

SATURDAY SUNDAY MONDAY & TUESDAY
2-moderate 2-moderate

DANGER SCALE

WIND & PERSISTENT SLAB:

Elevation: 2500′ and above
Aspect: Mostly south and lee to outflow flow wind, but all suspect
Terrain: Ridgelines, rollovers, cross-loaded features
Sensitivity: Responsive
Distribution: Specific features
Likelihood (Human Triggered): Likely
Size: Small to Medium
Danger Trend: Increasing with offshore blowing snow
Forecaster Confidence: Good
Details: North wind is creating new slabs and adding weight and stress on persistent facets (sugar snow) lower in the snowpack.

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 foot or more of new snow was available for transport after being deposited with strong, SE, onshore winds with the last storm. Properly investigate new wind slabs (soft & firm) from NE winds and see how well they are bonding to the snow below. These slabs have released naturally and stepped down to deeper, persistent, weak layers. Both mid-pack and ground level facet layers have previously failed in testing.

20161202 Strong Outflow Winds

20161202 Strong Outflow Winds

20161202 Outflow winds at the gap

20161202 Outflow winds at the gap

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

  • Clear skies revealed a scattering of naturally releasing avalanches due to wind loading on mostly southerly aspects with one northerly exception:
    • 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): -7/10
Ridgetop Wind Forecast (mph):  NE/15-60
Snowfall (in): Trace
WIND & TEMPERATURE Past 24 Hours: Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 20 / N 38 / NE
Max Wind Gust (mph) / Direction 36 / NE 53 / NE
Temperature Min / Max (*F) 26 / 41 10 / 24

Cold, clear and cranking winds will be the order for the weekend as temperatures will continue to drop into next week. This will be the coldest weather of the season yet, so plan ahead when venturing outside: highs of -15F* on the pass by Monday. Combining that with brisk winds nearing 70mph on Thompson Pass, keeping warm will be a challenge. There is a slight chance that a few snowflakes could fall tonight, and even slightly more Monday night, but don’t expect much.

Additional Info & Media

SNOW HISTORY: Valdez 12/3 AM Thompson Pass 12/3 AM
24 Hour Snow / Water Equiv.  0” /0″ 0″ /0″
Storm Snow /Water Equiv. (11/30-12/1) 19” /1.4″ 12?″ /?″
Current Snow Depth 20″ ?″
December Snow / Water Equiv. 19″ / 1.4″ 12?″ / ?″
Total Winter Snowfall / Water Equiv. 41″ / 5.5” 80?″ / 8.8?″
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 (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 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.

Forecaster: Kevin Salys