Monday-Thursday 4/17-4/20

Issued: Mon, Apr 17, 2017 at 8AM

Expires: Thu, Apr 20, 2017

Plan your mountain adventures with knowledge that daytime warming weakens and loosens the snow. Avoid steep solar affected slopes in late afternoon. Give cornices wide berth.

Sagging snowbridges and low ground near crevassed areas on glaciers should be avoided.

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

MONDAY TUESDAY WEDNESDAY & THURSDAY

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: 

It has been over a week since the last significant precipitation. Our snow has typical springtime variability. Preserved, settled powder is still being found on upper elevation northerly aspects. Everywhere else is a mixed bag of texture and depth due to wind and sun affect. While the valley snow is melting quickly, average snowpack depth is still more than three feet near Thompson Pass. The north outflow wind has been keeping surfaces cool. The exception is solar aspects that are steeper than about 35 degrees where a meltfreeze cycle is thawing during the day and re-freezing at night, causing the wet loose activity we’ve been seeing peel the layers down like an onion. Reports of some cornice failure – give cornices wide berth.

Snow transport Wed, Apr 14 from strong NE outflow.

Expect small pockets of windslab built by northeast wind near ridgetops. Inspect how the windslab is attached to the varied surfaces below.

Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

Maritime (Coastal) Specific:

  • 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
  • April 7: new natural west aspect in the Books.

      Photo: Bobby Lieberman
  • April 6-8: many wet loose avalanches on south aspects 4500′ and below stepped down and pulled out the last storm slab to old firm surfaces. These large size D3 avalanches ran full path. A few reports of similar activity above 4500′.

More fresh releases off Girls Mountain south face.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  19 / 31
Ridgetop Wind Forecast (direction/mph):  NE / 5-40
Snowfall (in/water equivalent):  0″ / 0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  2 / NE  20 / NE
Max Wind Gust (mph) / Direction  5 / NE  26 / NE
Temperature Min / Max (*F)  31 / 44  27 / 37

Weather Forecast:     Warm sunny days with freezing overnight.  Valley highs in the mid 40s F. No precipitation until Friday. Northeast wind to 40mph at ridgetops and passes.

Additional Info & Media

SNOW HISTORY: Valdez 4/17 AM Thompson Pass 4/17 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 22″ 40″
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.
Sarah Carter

Forecaster: Sarah Carter