Saturday-Tuesday 3/17-3/20

Issued: Sat, Mar 17, 2018 at 8AM

Expires: Tue, Mar 20, 2018

Above 2,500ft Considerable

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
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:   Responsive
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small – Large
Danger Trend:   Steady
Forecaster Confidence:    Good

STORM SNOW:
Elevation:
   All
Aspect:
   All  
Terrain: 
  30+ degrees steepness
Sensitivity:
   Responsive
Distribution:   
Widespread
Likelihood (Human Triggered): 
 Possible-Likely
Size:   
Small – Large
Danger Trend:
   Steady
Forecaster Confidence:
    Good

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

As much as 2.5′ (80cm) of snowfall has condensed from March 9 – 14. These recent storm snow events are proving responsive to human trigger on slopes above 30 degrees.  Additionally we have light rain effect up to 4000′ from the evening of March 14 creating dense surface conditions and producing pinwheels 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.

Below 2000′ the temperatures have been hovering around freezing and often slightly above freezing during the day.  Add rain and/or heavy snow to the relatively warm temperatures and the chances of wet avalanches increase.  We’ve been seeing signs of Loose-wet activity and suspect with more rain and/or above freezing temperatures we’ll likely see wet slab avalanches below tree line.

 

Recent Avalanche Activity

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): 25 / 30
Ridgetop Wind Forecast (direction/mph): NE /0-7
Snowfall (in):  0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  1 / NE   12 / SE-NE
Max Wind Gust (mph) / Direction  5 / NNE  32 / SE
Temperature Min / Max (*F)  31 / 36  24 / 30

Weather Forecast:    Saturday – Clear to partly cloudy with calm to light winds expected through the weekend.  Clear to partly cloudy Sunday.  Precipitation possible Monday.  Temperatures above freezing around the port during the day, and in the 20’s and 30’s  above 2500′.

Additional Info & Media

SNOW HISTORY: Valdez 3/17 AM Thompson Pass 3/17 AM
24 Hour Snow / Water Equiv. 0”/ 0.15″ 0.5″ / 0.01″
Storm Snow /Water Equiv. (3/9-14) 19” / 0.41″ 40″ / 1.5″
Current Snow Depth 35″ 79″
March Snow / Water Equiv. 20″ / 2.53″ 33″ / 1.61″
Total Winter Snowfall / Water Equiv. 132.54″ / 26.75” 356″ / 34.6″
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.

Forecaster: Ryan Van Luit