April 29-30, 2018

Issued: Sat, Apr 28, 2018 at 8AM

Expires: Mon, Apr 30, 2018

The last forecast for the Valdez Avalanche Center advisory area will be issued on Monday, April 30. Please join us May 2 for the annual Valdez Avalanche Center membership meeting. Backroom of Mike’s Palace 5pm. Bring your feedback and ideas for improving the avalanche forecast and educational outreach programs for our community.

Above 2,500ft Considerable

1,800 to 2,500ft Moderate

Below 1,800ft Low

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

DANGER SCALE

Wind Slab:
Elevation:   Above 2500′
Aspect:   W-N
Terrain:   Lee of ridges, gullies, ridge tops exposed to wind
Sensitivity:   Stubborn
Distribution:   Specific
Likelihood (Human Triggered):   Likely
Size:   Small – Large
Danger Trend:   Steady
Forecaster Confidence:    Fair

Storm Snow:
Elevation:   Above 2500′
Aspect:   All
Sensitivity:   Stubborn
Distribution:   Widespread
Likelihood (Human Triggered):  Possible – Likely
Size:   Small – Large 
Danger Trend:   Steady
Forecaster Confidence:    Good

Wet Avalanches:
Elevation:   Below 3000′
Aspect:   SE – S – SW
Sensitivity:   Non-reactive when frozen – Responsive when warmed by above freezing temps, direct solar input, or rain
Distribution:   Specific – Widespread
Likelihood (Human Triggered): Possible
Size:   Small – Large
Danger Trend:   Increasing with rain, direct solar input, and above freezing 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 4/20-29 spring storm has laid down more than three feet/1 meter of new snow above 4000′. This new snow was transported yesterday by moderate southeast wind at Thompson Pass and upper elevations. 4.07″ of rain has fallen at sealevel since April 20.

Previous to this latest snow event, windslabs were created lee of ridges, gullies and ridge tops. The windslabs and storm snow are slow to bond to older surfaces, especially on NE – N – W aspects.

Below the most recent storm snow, the snowpack varies from isothermic, to relatively dense throughout (1-4F).  Some N facing aspects above 3000′ held onto a pencil hard layer at the interface. There have been two human triggered avalanches in the last week that failed at the old snow/new snow interface.

The freezing level has been fluctuating between 1500′-3000’+ throughout the past week.

Snow depths generally range from 30-250cm, including on glaciated terrain.

Check out our public observations.

Recent Avalanche Activity

Low visibility Saturday did not allow for observation of new activity.

4/26-27:  Numerous natural D1 windslab and wet avalanches between 2000′ and 5000′ on all aspects.

Two D2 windslab avalanches observed on NW facing slopes between 2500′-4000′.

4/25: Unintentional skier triggered avalanche reported in our public observations.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F): 27 / 31
Ridgetop Wind Forecast (direction/mph): S / 3-27
Snowfall (in):  0-2”
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  3 / VAR   15/ SE
Max Wind Gust (mph) / Direction  7 / WSW  28 / SE
Temperature Min / Max (*F)  34 / 36  25 / 28

Weather Forecast:       Broken visibility.   Light to moderate winds from the southeast.  Temperatures hovering around freezing near Thompson pass and into the upper 30’sF (1-3*C) near the port of Valdez.  Intermittent rain and snow will continue through the week with freezing levels ranging from 1500′-3000′.

Additional Info & Media

SNOW HISTORY: Valdez 4/29 AM Thompson Pass 4/29 AM
24 Hour Snow / Water Equiv. 0”/ 0.37″ 2″ / ?″
Storm Snow /Water Equiv. (4/21-29) 0” / 3.98″ ?″ / ?″
Current Snow Depth 0″ 58″
April Snow / Water Equiv. 0″ / 4.07″ 19″ / 0.7″
Total Winter Snowfall / Water Equiv. 132.59″ / 31.18” 393″ / 37.4″
Snowload in Valdez ~ 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.
Sarah Carter

Forecaster: Sarah Carter