Monday-Thursday 1/28-2/1

Issued: Mon, Jan 29, 2018 at 8AM

Expires: Thu, Feb 01, 2018

Gap wind at Thompson Pass hit 84 mph Sunday causing considerable snow transport. Avoid crossloaded gully walls and actively loading lee features. If the snow begins to get stiff, sound hollow, or you see shooting cracks, choose another slope without wind affect. In wind protected zones, dig and test for the persistent weak layer between 2 and 4′ below the surface.

Above 2,500ft Moderate

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
2-moderate 2-moderate

DANGER SCALE

 

 

WIND SLAB:
Elevation:
   Above 2000′
Aspect:  
 Lee of ridges, gullies, ridgetops
Terrain: 
  All terrain exposed to wind
Sensitivity:
   Responsive
Distribution:   
Specific
Likelihood (Human Triggered): 
Possible
Size:   
Small – Large
Danger Trend:
 Steady
Forecaster Confidence:
   Good

PERSISTENT SLAB:
Elevation:
   Above 2500′
Aspect:
   All
Terrain: 
  35+ degrees steepness
Sensitivity:
   Stubborn
Distribution:   
Specific
Likelihood (Human Triggered):   
Possible
Size:   
Small – Large
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, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION: 

Strong northerly outflow wind continues to redistribute surface snow and build fresh wind slab.  Sunday, Jan.28 several natural windslab avalanches were observed in steep terrain above 3000′, lee to channeled outflow wind. Expect slopes with fresh windslab to be sensitive to human trigger, especially with the weight of multiple people and/or sleds.

Our last notable storm was Jan.13-16 with totals ranging from 18’’ (46cm) near Kenny Lake/Chitina to 41’’ (104cm) at Thompson Pass. Expect scoured ridgelines, while lee slopes could have very deep pockets of fresh windslab.

Previous to the Jan.13-16 storm there were concerns of a persistent weak layer about 1-2’ under the snow surface. This persistent weak layer (surface hoar and/or near-surface facets) is now buried 2-4’ down.  We suspect this layer may persist in upper elevations primarily where wind had less effect.  We encourage you to dig for and test this layer, especially above 3000′.  Jan.26 on a NW aspect across from Rice Mountain at 3200′, we found this layer 28″ (70cm) below the snow surface and it was stubborn to trigger. This layer was confirmed by another party Sunday January 28 closer to Thompson Pass. It was found 32″ (80cm) down and failed when tested.

Below 2000′ (the rainline from the Jan.13-16 storm) the snow is frozen in place with a beefy crust.

Recent Avalanche Activity

January 28: several size 1-2 windslab avalanches observed lee to north outflow wind, mostly off ridgelines and gully walls above 3000′ through the Thompson Pass corridor.

Jan.28, 2018 Natural windslab avalanche on west facing gully wall above MP 33. Ryan Van Luit photo.

Wind transport Jan.28, 2018. Ryan Van Luit photos.

 

January 19, a snowmachiner triggered an avalanche size D2 between Heiden Glacier (near “The Books”) and Deserted Glacier. The weak layer may have been near-surface facets.

  • NW aspect
  • ~35< slope
  • ~5000′ in elevation
  • 1-3′ (30-91cm) crown
  • No injuries reported

See photo and map below.  Photo credit: Clyde Hewitt.

Several small windslab avalanches size D1 were observed Thursday Jan.18 at 3200′, visible from the Loveland parking lot to the lee of gullies.  These seem to have been naturally triggered and were likely a day or two old.  All of them were facing southeast, which indicate they were created by a northerly outflow wind.

 

 

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -5/ 5
Ridgetop Wind Forecast (direction/mph): N / 18-54
Snowfall (in): 0
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   10/ NE  56 / NE
Max Wind Gust (mph) / Direction  21 / NE  84/ NE
Temperature Min / Max (*F)  13 / 19  -9 / 11

Weather Forecast: Clear and cold. Strong-extreme northerly outflow wind continues. No significant pattern change for a week or so.

Additional Info & Media

SNOW HISTORY: Valdez 1/29 AM Thompson Pass 1/29 AM
24 Hour Snow / Water Equiv. 0”/ 0″ 0″ / 0″
Storm Snow /Water Equiv. (1/13-16) 2” / 2.82″ rain 41″ / ~3″
Current Snow Depth 23.5″ 75″
January Snow / Water Equiv. 12.78″ / 6.02 ″ 83″ / ~6.5″
Total Winter Snowfall / Water Equiv. 77.64″ / 22.05” 290″ / ~30″
Snowload in Valdez 37 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS / STORM TOTAL (Jan.13-16) / STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 22″ / ?”
Upper Tsaina at 1750 ft (in): 0″ / 19″ / 2″
Sugarloaf at 550 ft (in): 0″ /rain” / ?”
SNOW DEPTH & WATER SURVEY (2/1/2017) 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.

Weather Quicklinks:

 

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, Intermountain Forecasts, Maritime Forecasts.
Sarah Carter

Forecaster: Sarah Carter