Sunday-Wednesday 3/18-3/21

Issued: Sun, Mar 18, 2018 at 8AM

Expires: Wed, Mar 21, 2018

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

Sunday Monday Tuesday
& Wednesday
2-moderate 2-moderate

DANGER SCALE

 

WIND SLAB:
Elevation:   Above 2000′
Aspect:   Lee of ridges, gullies, ridgetops
Terrain:   Upper elevation terrain exposed to wind
Sensitivity:   Stubborn
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small – Large
Danger Trend:   Steady
Forecaster Confidence:    Fair

WET AVALANCHES:
Elevation:
   Below 2000′
Aspect:
   All  
Terrain: 
  30+ degrees steepness
Sensitivity:
   Stubborn to Responsive
Distribution:   
Widespread
Likelihood (Human Triggered): 
Possible-Likely
Size:   
Small – Large
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

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION:     As much as 2.5′ (80cm) of snow fell March 9 – 14 with new windslabs responsive to human triggers on slopes steeper than 30 degrees. Direct solar radiation at all elevations exposed to the sun as well as rainfall in the lower elevations has triggered new snow instabilities and point release wet avalanches on all aspects.

The Feb. 27 – March 1 wind event created pencil hard surface conditions in many areas, especially in the alpine. Due to this significant hardness difference (with the newer snow), and because it’s still within the top 3′ (1 meter) of the snowpack, we’re keeping a close eye on this interface.

Several human triggered whumpfs occurred above 2500′ elevation NW aspect above Milepost 34 where tests of the weakness produced an ECTP 13 Q1 result.

Below 2000′ the temperatures have been hovering around freezing and often slightly above freezing during the day.  Warm temperatures increase the chances of wet avalanches. Loose wet snow avalanches may develop from point releases to slab avalanches below tree line.

 

Recent Avalanche Activity

March 17: D2 Wind slab, upper elevation, north aspect inter-mountain snow climate zone, accidental human triggered one foot deep, 30 feet wide, ran 450 feet.
March 16: D1 Storm slab, intentional human triggered.
March 14: D2 Storm slab, intentional human triggered.
March 12: D3 to valley floor off Mt Tiekel at Milepost 50.
March 12: D2 storm slab Avalanche ~4000′ near milepost 35.
March 10: Human triggered D1 avalanche on the Road Run with lucky outcome; see Observations <here> thank you Jen Milton.

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F): 22 / 28
Ridgetop Wind Forecast (direction/mph): S /5-25
Snowfall (in):  1-3″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  1 / NE   15 / SW
Max Wind Gust (mph) / Direction  11 / NE  35 / NE
Temperature Min / Max (*F)  29 / 42  22 / 32

Weather Forecast:    Flurries developing Sunday, overnight producing a few inches by mid-day Monday.  Mild temperatures with specks of rain below 1000′ elevation. The skies will clear Tuesday bringing hurricane force northerly outflow winds for the remainder of the forecast period.

Additional Info & Media

SNOW HISTORY: Valdez 3/18 AM Thompson Pass 3/18 AM
24 Hour Snow / Water Equiv. 0”/ 0.03″ trace″ / 0″
Storm Snow /Water Equiv. (3/9-14) 19” / 0.41″ 40″ / 1.5″
Current Snow Depth 33″ 82″
March Snow / Water Equiv. 20″ / 2.56″ 44″ / 3″
Total Winter Snowfall / Water Equiv. 132.54″ / 26.93” 367″ / 36″
Snowload in Valdez 55 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.
Pete Carter

Forecaster: Pete Carter