Monday-Thursday 4/10-4/13

Issued: Mon, Apr 10, 2017 at 8AM

Expires: Thu, Apr 13, 2017

It’s spring! Daytime warming loosens and lubricates the snow increasing avalanche danger. Avoid steep slopes late in the afternoon, especially those being baked in direct sunshine or warmed by cloud cover creating the greenhouse effect.

Friday April 14: VAC Full Moon Spring Fling FUNraiser with Acoustic Avalanche at the Tsaina Lodge   Grab a date and come boogie!

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& THURS

DANGER SCALE

 

WET AVALANCHES:
Elevation:
   Below 5000′
Aspect:
   East in AM, bearing South, 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 at night
Forecaster Confidence:
   Good

PERSISTENT SLAB:
Elevation:
  Above 2500′
Aspect:
 All
Terrain:
Slopes > 35*
Sensitivity:
   Stubborn on northerlies, Touchy when warmed by sun
Distribution:
   Widespread
Likelihood (Human Triggered):
   Possible
Size:
  Small – Large
Danger Trend:
   Decreasing
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: 

Monitor where surface hoar and near surface facets are being buried by fresh flurries.

The storm that ended April 6 laid down 2-4 inches of water equivalent; 3-4 feet of snow up high on the coastal side with rain below ~3600′. That storm snow is settling and bonding relatively well to old layers. The exception is a few upper elevation areas where buried near surface facets are still reactive.  South wind during that storm formed new cornices and some pockets of windslab near and below ridgelines.

The tail end of the storm April 4-6 pushed temperatures above freezing to 4500′ on the north side of the pass and up to 5500′ in the maritime. Daytime green house effect (short wave radiation bouncing between the snow surface and cloud cover) and periods of direct sunshine caused wet loose activity to entrain and step down, releasing slab avalanches to size D3. In really shallow areas, wet loose has scoured directly to the ground.

Persistent slab problems are still a concern in colder, thinner and more continental areas. The structure is very poor and the potential for a storm slab or hard slab to step down to weak basal facets is scary. Continue to monitor this structure as temperatures rise and weaken the firmer, overlaying structure. In addition keep an eye on surface hoar and near surface facets as these could be of concern should they be buried by additional snowfall.

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

Recent Avalanche Activity

Maritime (Coastal) Specific:

  • 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′.

Large wet debris running far into flats on south side of Tone’s Temple

Slabs pulling out from wet loose off of southerlies along Worthington Glacier

More fresh releases off Girls Mountain south face.

  • April 2: a scattered few human triggered soft slab avalanches up to D2: failed both within new snow (E-NE) and at new-old snow interface (SW)
  • March 31: Many small (D1) loose wet avalanches around the port and in Keystone Canyon.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  25 / 35
Ridgetop Wind Forecast (direction/mph):  NE / 5-20
Snowfall (in/water equivalent):  1-2″ / Trace”
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  3 / Var  10 / Var
Max Wind Gust (mph) / Direction  6 / NE  20 / NE
Temperature Min / Max (*F)  33 / 39  20 / 29

Weather Forecast:     Chance of a snowflake. Clearing Tuesday evening. Freezing level remaining around 1500′ elevation.

Additional Info & Media

SNOW HISTORY: Valdez 4/9 AM Thompson Pass 4/10 AM
24 Hour Snow / Water Equiv.  0”/0.0″ trace” /trace″
Storm Snow /Water Equiv. (3/27-4/6)  16.9″ /4.1″ 24″ /2.4″
Current Snow Depth 37″ 42″
April Snow / Water Equiv. ~″ /1.82″ 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 (4/8 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.

Forecaster: Contrad Chapman