Friday-Sunday April 7-9

Issued: Fri, Apr 07, 2017 at 9AM

Expires: Sun, Apr 09, 2017

Arctic Man 2017
Always wear a beacon, shovel and probe while traveling in the mountains. With low coverage, sled and trauma from crashes are more likely than avalanches.

Friday April 7 11am-1pm to practice your Avalanche Rescue Skills. Stop by the Avalanche information kiosk; we’re across from the showers on the corner of Racer’s Row, not too far from the beer tent.

Above 4,000ft Low

3,000 to 4,000ft Low

Below 3,000ft Low

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

FRIDAY SATURDAY SUNDAY

DANGER SCALE

 

WIND SLAB OVER PERSISTENT WEAK LAYER:
Elevation:   Above 3000″
Aspect:  Lee to north wind
Terrain:   Near ridges, gully walls, rollovers
Sensitivity:   Stubborn
Distribution:   Specific
Likelihood (Human Triggered):   Unlikely
Size:   Small – Large
Danger Trend:   Steady
Forecaster Confidence:   Fair

WET LOOSE AND WET SLAB AVALANCHES:
Elevation: Above 3000″
Aspect: slopes absorbing the sun’s heat, south and west in the afternoon
Terrain: Steeps >40 degrees
Sensitivity: Responsive
Distribution: Specific
Likelihood (Human Triggered): Possible
Size: Small – Large
Danger Trend: Increasing in afternoon
Forecaster Confidence: Good

A few wet loose ran in the steeps Thursday afternoon April 6. Photo: Sarah Carter

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

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION: Very thin snow coverage surrounding the Summit Lake area; 20 inches average snowpack depth.  Below 4000′ the snow became close to isothermal yesterday – facets quickly turned to wet grains.

Above 4000′ ridgelines and gullies are windloaded from north wind events back in March and earlier. 2-8 inches snow fell April 1st  leaving a bit of fresh on top.  Under the new snow, the snow structure is pencil-1 finger (hard/strong) windslab layers over 4finger-fist (weak) facets and depth hoar. Not much potential for propagation has been observed though.

evidence of old avalanche activity in upper elevations Photo: Sarah Carter

Video showing layers of hard cohesive snow over weak punchy facets

 

 

Recent Avalanche Activity

Yesterday in the late afternoon a few wet loose avalanches were triggered both naturally and by humans on steeps that baked in the sun all day. The coverage is so thin, the wet snow peeled to ground.

Tuesday a snowmachiner triggered a small pocket of windslab on a steep sun-warmed slope. The crown was 6″- 2′ thick and released just under the ridge. The avalanche was a size 1, not large enough to bury & kill a person.

Recent Weather

Sunny today for the Arctic Man race. A few clouds possible. Temps in the 40s Fahrenheit near Summit Lake. Light north wind.

Additional Info & Media

SNOW HISTORY: Valdez 2/24 AM Thompson Pass 2/24 AM
24 Hour Snow / Water Equiv. <0″/0″ 0″ /0″
Storm Snow /Water Equiv. (2/22-2/23) 0.6” /0.05″ 1″ /0.1″
Current Snow Depth 48″ 49″
February Snow / Water Equiv. 44.9″ /5″ 43″ / 5.1″
Total Winter Snowfall / Water Equiv. 222.8″ /20.9” 282″ / 27.7″
Snowload in Valdez ~ lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (2/24 AM)/STORM TOTAL (2/22-23)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 0″ / 0″
Upper Tsaina at 1750 ft (in): 0″ / 0″ / 0″
Sugarloaf at 550 ft (in): 0″/ 1″ / 0.1″
SNOW DEPTH & WATER SURVEY (2/1/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.5″  9.8″
Milepost 18 43.9″ 9.5″
Milepost 29 Worthington Flats 61.5″ 16″
Milepost 37 Tsaina River bridge 42.1″ 9.3″
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:

  • coastal-zone-iconMaritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  • intermountain-zone-iconInter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  • interior-zone-iconContinental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).

Photo of Thompson Pass

thompson-pass-ski-runs

Interactive Map of Valdez Forecast Areas w/ Many Resource Layers (Trevor Grams)

climate-zones-topoclimate-zones-satellitegoogle-earth1

Run Map of Thompson Pass Area (Sean Wisner) (2MB download)
VAC Run Map Thompson Pass

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 EARAC Forecasts.
Sarah Carter

Forecaster: Sarah Carter