Tuesday-Friday 1/30-2/2

Issued: Tue, Jan 30, 2018 at 8AM

Expires: Fri, Feb 02, 2018

70 MPH wind gusts with an average of 62 MPH on Thompson Pass the last 24 hours. The most likely place you will trigger an avalanche is areas like gullies, chutes, ramps, ridges, rollovers, and cornices that have been snow loaded by the strong recent winds.

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

Tuesday Wednesday Thursday
& Friday
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.

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -6/ 5
Ridgetop Wind Forecast (direction/mph): N / 18-60
Snowfall (in): 0
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   20/ NE  62 / NE
Max Wind Gust (mph) / Direction  40 / NE  70/ NE
Temperature Min / Max (*F)  23 / 28  7 / 10

Weather Forecast:  All of Alaska is experiencing an extreme wind event from the North. Be prepared for cold temperatures and a dangerous windchill, plus a bit of cloud cover here or there. Things are looking grim for the Valdez/Thompson Pass region the rest of this week.

Additional Info & Media

SNOW HISTORY: Valdez 1/30 AM Thompson Pass 1/30 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.
Kyle Sobek

Forecaster: Kyle Sobek