Tuesday-Friday 4/18-4/21

Issued: Tue, Apr 18, 2017 at 8AM

Expires: Fri, Apr 21, 2017

Cornices are starting to fall, bringing the entire seasons snowpack down in a massive avalanche. Winds are picking up creating fresh windslab.

Above 2,500ft Moderate

1,800 to 2,500ft Moderate

Below 1,800ft Moderate

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 5500′
Aspect:
   East in AM, South all day, then West in PM
Terrain:
Steep terrain near rocks and vegetation.
Sensitivity:
   Touchy when warmed.
Distribution:
   Specific.
Likelihood (Human Triggered):
  Possible
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

WIND SLAB:
Elevation:   Above 3000′
Aspect:   Southerlies
Terrain: Near ridgelines, rollovers and gully walls.
Sensitivity:   Responsive to Touchy when sitting on sun crust.
Distribution:   Specific.
Likelihood (Human Triggered):  Possible
Size:   Small
Danger Trend:  Steady
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 snow is starting to melt off in the lower and mid elevations especially areas with lots of sun exposure. Above 4000′, the more northerly aspects, and glaciated areas, powder snow can be found. Generally speaking, the maritime zones have seen much more snow than the intermountain/continental zones. This has led to a deeper more stable snowpack. With winds picking up today and yesterday, there is a possibility of some fresh windslab popping off near peaks and ridges. The winds should keep things a little cooler than the last few days, but with the amount of sun at this time of year, wet avalanches are always a concern.

Snow transport Wed, Apr 14 from strong NE outflow.

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Recent Avalanche Activity

Maritime (Coastal) Specific:

  • 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 12: Numerous natural, wet loose avalanches to size D2.5 from Marshall Pass to the port, large running slides down the south faces west of Mineral creek to the flats/sea level. Many running to ground with dirty debris.
  • April 11: With more direct sun, more wet loose releasing out of steep, south aspects entraining snow to D2.5, sometimes to ground

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

    Natural West facing avalanche in, “The Books” Photo: Bobby Lieberman

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  17 / 28
Ridgetop Wind Forecast (direction/mph):  NE / 10-40
Snowfall (in/water equivalent):  0″ / 0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  5 / E  22 / NE
Max Wind Gust (mph) / Direction  11 / E  37 / NE
Temperature Min / Max (*F)  32 / 52  24 / 34

Weather Forecast:  Winds are increasing which are keeping temperatures cool. North winds up to 40MPH winds at 3000′ today which could mean 50+ on ridge tops. No new precipitation forecasted until this upcoming weekend.

Additional Info & Media

SNOW HISTORY: Valdez 4/18 AM Thompson Pass 4/18 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 19″ 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 (4/17 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