Tuesday-Friday 4/25-4/28

Issued: Tue, Apr 25, 2017 at 8AM

Expires: Fri, Apr 28, 2017

Springtime conditions exist: avalanche danger increases with daytime warming and solar radiation.

Storm slab potential is increasing as the new snow gains depth and is distributed with the wind.

Above 2,500ft Considerable

1,800 to 2,500ft Considerable

Below 1,800ft Considerable

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

DANGER SCALE

 

 

WET AVALANCHES:
Elevation:
   Below 6000′
Aspect:
   All steep terrain, especially aspects that have direct sun
Terrain:
Slopes >35 degrees near rocks and vegetation.
Sensitivity:
   Touchy when warmed.
Distribution:
   Specific.
Likelihood (Human Triggered):
  Likely when warmed.
Size:
  Small-Large
Danger Trend:
   Increasing quickly each day with warming temperatures, falling with freezing at night
Forecaster Confidence:
   Good

CORNICE FALL:
Elevation: 
ALL
Aspect:   
ALL
Terrain:
corniced ridgelines
Sensitivity:   
Responsive 
Distribution:   
Specific
Likelihood (Human Triggered): 
Possible
Size:  
Small to Large
Danger Trend: 
Increasing
Forecaster Confidence: 
 Fair

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:

Maritime (Coastal) Specific: 

The spring shed is in progress. Over the past week, daytime temperatures have reached into the 50s in the valley bottoms. Most of our remaining Chugach snow has been freezing at night and thawing during the day. This means crusts and lots of isothermal snow below 3000′.

Having just finished a 19-day dry spell, the bit of rain and snow this week will freshen our snow world. If the 1/4″ of precipitation comes our way, we can expect rain to about 4000′ with snow above. With warm temps the new snow should bond quickly. An exception will be upper elevations with a sun crust come bed surface. When the sun pops out again toward the weekend, expect fresh loose avalanches and the possibility of new wet slab.

A tour of the Woodworth and Deserted Glaciers Sunday April 23 showed increased flow in the creeks, lots of cornice failure, and some new wet slabs in the upper elevations on sunny aspects.

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Recent Avalanche Activity

Maritime (Coastal) Specific:

  • April 23 Natural wet slab D2.5 above Deserted Glacier, west aspect, 5800′. Lots of south and west cornice failure and wet loose activity into the Woodworth and Deserted Glaciers.

    April 23: fresh wet slab at 5800′ on west aspect above Deserted Glacier        Photo: Sarah Carter

  • April 17 The Wall/Tomahawk rockfall resulting in D3+ avalanche.
  • April 13-16 More wet loose activity in the afternoon on steep solar affected slopes

  • April 18th  “Things are coming unglued out there” Photo: Jeremy Martin

  • Large avalanche on, “The Wall/Tomahawk” caused by rockfall Photo: Jed Workman

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  32 / 39
Ridgetop Wind Forecast (direction/mph):  SE / 10-20
Snowfall (in/water equivalent):  0.24″ / 0-3″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  5 / E  10 / SE
Max Wind Gust (mph) / Direction  10 / E  22 / SE
Temperature Min / Max (*F)  40 / 50  31 / 43

Weather Forecast: Rain in the morning in town, with the snow line around 4000+  feet. The precipitation is supposed to taper off through out the day.

Additional Info & Media

SNOW HISTORY: Valdez 4/24 AM Thompson Pass 4/24 AM
24 Hour Snow / Water Equiv.  0”/0.0″ 0″ /0″
Storm Snow /Water Equiv. (3/26-4/9)  16.9″ /4.1″ 24″ /2.4″
Current Snow Depth 6″ 39″
April Snow / Water Equiv. trace″ /1.82″ rain 8″ / 0.8″
Total Winter Snowfall / Water Equiv. 239.8″ /24.47” 327″ / 31.4″
Snowload in Valdez 65.0 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (4/24 AM)/STORM TOTAL (3/27-4/6)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / ~16″ / ?”
Upper Tsaina at 1750 ft (in): 0″ / ?” / 1.2+”
Sugarloaf at 550 ft (in): 0″/ 20+rain” / 2.8″
SNOW DEPTH & WATER SURVEY (4/2/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.9″  11.9″
Milepost 18 40″ 11.9″
Milepost 29 Worthington Flats 62.2″ 19.6″
Milepost 37 Tsaina River bridge 46.3″ 12.5″
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 Maritime Forecasts.
Kyle Sobek

Forecaster: Kyle Sobek