Thursday-Sunday 2/23-26

Issued: Thu, Feb 23, 2017 at 9AM

Expires: Sun, Feb 26, 2017

Expect new windslabs drifted onto a variety of slopes by variable winds. These are likely forming on top of widespread weak crystals from our long clear, cold spell.

Take the time to investigate for weak sugar snow (facets) under new, firmer slabs. Where this combination is found, the whole snowpack has the potential to release dramatically to ground.

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

THURSDAY FRIDAY SATURDAY & SUNDAY

DANGER SCALE

 

WIND SLAB:
Elevation:
  Above 3000′
Aspect:
   Variable with shifting winds
Terrain:
  Near ridgelines, rollovers, and gully walls
Sensitivity:
  Responsive
Distribution:
Specific
Likelihood (Human Triggered):
  Possible
Size:
Small – Large
Danger Trend:
  Steady
Forecaster Confidence:
  Fair

PERSISTENT SLAB:
Elevation:
  All
Aspect:
  All
Terrain:
Most
Sensitivity:
  Non-reactive
Distribution:
  Widespread
Likelihood (Human Triggered):
  Unlikely
Size:
  Small – Large
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, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Continental (Interior) Specific: 

While four feet of new snow can be found at 56 mile last week, consider that rain impacted most of that to approximately ~2800′ during last week’s warm and wet storm. Since the rain, only a few inches of soft snow have fallen.

The upper elevations have limited observations but sugar snow is likely to dominate a large part of this zone.  If you find this sugar snow buried under firmer layers, be aware that everything above that could potentially release, even if the sugar snow is at the ground. This persistent slab avalanche problem is incredibly challenging to predict -> The likely hood is low for them to occur, but if they do the consequences are high.

Over the long calm, clear and cold spell last weekend, widespread surface hoar and near surface facets formed throughout our region. As few more inches fell and and winds picked up, investigate how these weak crystals are reacting once they get buried. Evaluate and test new slabs readily, for these buried crystals can persist and lead to problems for extended periods of time….leading to unpredictable and large avalanches.

Crudbusters Surface Hoar to 6mm

Find more photos and observations at the bottom of the page. Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

Continental (Interior) Specific: 

  • No slab avalanches have been observed as of 2/18 above timberline, but VERY limited observations have been made.
  • 4′ of new snow reported at 56 mile last week below timberline, rain has fallen on this new snow.
  • Rain fell above timberline all the way through Pump Station 12 and into Kenny Lake (last week)

Recent Weather

See Maritime Zone for updated weather.

Additional Info & Media

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 Continental Forecasts.

Forecaster: Kevin Salys