Saturday-Tuesday 4/14-4/17

Issued: Sat, Apr 14, 2018 at 8AM

Expires: Tue, Apr 17, 2018

Thanks to everyone who participated in the VAC fundraiser last night at the Tsaina Lodge!

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

Saturday Sunday Monday & Tuesday

DANGER SCALE

Wet Avalanches:
Elevation:   Below 4500′
Aspect:   SE – S – SW
Terrain:   Southerly facing terrain on slopes above 30 degree slope angle
Sensitivity:   Non-reactive – Responsive as sun and warmer temperatures dominate
Distribution:   Specific
Likelihood (Human Triggered): Possible
Size:   Small – Large
Danger Trend:   Increasing with solar input and warmer temperatures
Forecaster Confidence:    Good

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: The forecast region is experiencing a spring shed cycle, particularly below 4500′.  Temperatures around Thompson Pass have been above freezing during the day, and barely freezing over night.  This cycle can produce corn snow but is also the precursor to surface instability and an isothermic snowpack.

Snow surface conditions above ~3000′ are widely variable.  Conditions on northerly facing slopes range from wind scoured pencil hard sastrugi, melt/freeze, to decomposing unconsolidated particles.  Southerly faces are experiencing a range from heavy wet snow, to melt freeze crusts, to corn, to isothermal.

Snow depths generally range from 30-300cm, including on glaciated terrain.

Check out our public observations!

Recent Avalanche Activity

Numerous southerly facing slopes above 30* slope angle are experiencing natural wet avalanches from the port of Valdez up to 4500′ throughout the advisory area.  Most of this wet avalanche activity has been surface snow but could step down deeper into the snowpack.

Friday 4/13 PM: Three Pigs at Milepost 39 ran to the edge of the highway.

The conditions we’re experiencing lately don’t fit well with our North American Danger Scale.  We’re at a low danger in the mornings, with natural and human triggered avalanches unlikely. As the day progressively becomes warmer and solar input increases, the danger will spike.  When this happens, human and natural triggered avalanches become likely.

Video of Winds from 3/22/18

 

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F): 26 / 35
Ridgetop Wind Forecast (direction/mph): W / 0-8
Snowfall (in):  0”
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  3 / VAR   10 / VAR
Max Wind Gust (mph) / Direction  11 / WSW  18 / NE
Temperature Min / Max (*F)  35 / 49  30 / 38

Weather Forecast:      Clear to partly cloudy skies Saturday through Tuesday.  Temperatures in the Port of Valdez and at Thompson Pass into the 40’s F (4-9*C).  Light to moderate winds.

Additional Info & Media

SNOW HISTORY: Valdez 4/15 AM Thompson Pass 4/15 AM
24 Hour Snow / Water Equiv. 0”/ 0.0″ 0″ / 0.0″
Storm Snow /Water Equiv. (3/15-19) 19” / 0.41″ 40″ / 1.5″
Current Snow Depth 21″ 64″
April Snow / Water Equiv. 0″ / 0″ 0″ / 0″
Total Winter Snowfall / Water Equiv. 132.59″ / 27.2” 372″ / 36.6″
Snowload in Valdez 53 lbs/sq. ft.

 

SNOW DEPTH & WATER SURVEY (3/4/2018) Depth Snow Water Equivalent
Milepost 2.5 Valdez  32.2″  9″
Milepost 18 42″ 11″
Milepost 29 Worthington Flats 62.4″ 21.2″
Milepost 37 Tsaina River bridge 58.4″ 14.2″
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.

Forecaster: Ryan Van Luit