Saturday-Tuesday 1/28-1/31

Issued: Sat, Jan 28, 2017 at 8AM

Expires: Tue, Jan 31, 2017

The recent shifting back and forth of winds (onshore to outflow) has moved new snow onto a variety slopes in upper elevation, exposed terrain.

Evaluate how the storm snow and new wind slabs near ridgelines and roll-overs is bonding before committing to steep terrain.

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

SATURDAY SUNDAY MONDAY & TUESDAY

DANGER SCALE

STORM SNOW:
Elevation:
 All
Aspect: 
All
Terrain: 
Steeper than 35 degress
Sensitivity: 
Reactive
Distribution: 
Widespread
Likelihood (Human Triggered): 
Likely
Size: 
Small – Large
Danger Trend:
 Increasing 
Forecaster Confidence: 
Good

PERSISTENT SLAB:
Elevation: 
Mostly above 2500′
Aspect: 
All
Terrain: 
Steep rocky slopes where facets exist under old and between windslab, especially interior of Thompson Pass
Sensitivity: 
Stubborn
Distribution: 
Specific
Likelihood (Human Triggered): 
Unlikely
Size: 
Small – Large
Danger Trend: 
Increasing with load
Forecaster Confidence: 
Poor

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: While more rain soaked the lower elevations in town up to Keystone Canyon Friday (rain line was possibly up to 2500′ and pushed inland all the way to Milepost 19 Thursday), a total of ~2 feet of snow continued to stack up at the pass since Jan. 23rd. Highest numbers of new snow were near Thompson Pass proper, while those numbers were nearly halfed (~1 f00t) down near the Tsaina River and even less out at Milepost 46. The new snow seems to be sticking well to old snow surfaces (faceted sugar old snow, surface hoar, and windslab) buried Jan 23rd with no alarming failures in assessment (see new observation from Friday). With a variety of fronts pushing through this week, varying winds from the SE and then NE have been moderately drifting snow to lee slopes in the upper elevations. Soft wind slab formation on nearly all aspects in exposed terrain is likely compounding storm snow instabilities.

 Find more photos and observations at the bottom of the page. Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

coastal-zone-iconMaritime (Coastal):

  • Jan 26: Widespread wet snow releases (loose and slab) below the rain line: Above town and airport; Keystone Canyon; poor visibility limited observations
Highschool Hill Loose Wet Avalanches Thursday

Highschool Hill Loose Wet Avalanches Thursday

  • Jan 25: Storm snow instabilities: Keystone Canyon Steeps.

intermountain-zone-iconInter-Mountain (Transitional):  

  • No new observations.

interior-zone-iconContinental (Interior):  

  • No new observations.

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  15 / 25
Ridgetop Wind Forecast (direction/mph): Var / 5-20
Snowfall (in):  2-3
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   4 / Variable  ? / Variable
Max Wind Gust (mph) / Direction  13 / ENE  43 / NE
Temperature Min / Max (*F)  32 / 40  22 / 28

Weather Forecast:    Temperatures peaked to 40*F in town yesterday, bringing more rain to town that only pushed inland to Keystone Canyon. Variable winds will continue as cloudy skies and scattered flakes could accumulate to a few inches up on Thompson Pass. Clouds should begin to break up by early Sunday until a front hits us Monday night with a handful of inches of snow to add up by Wednesday morning. It seems that high pressure gradients are forecasted for the end of the week which could bring in some strong outflow winds over the passes.

Additional Info & Media

SNOW HISTORY: Valdez 1/28 AM Thompson Pass 1/27 AM
24 Hour Snow / Water Equiv. 0.1” /0.4″ 3″ /0.3″
Storm Snow /Water Equiv. (1/23-28) 24.7” /2.5″ 20″ /1.7″
Current Snow Depth 43.3″ 41″
January Snow / Water Equiv. 72.5″ /5.7″ 74″ / 5.9″
Total Winter Snowfall / Water Equiv. 168.6″ / 15.6” 217″ / 20.3″
Snowload in Valdez ? lbs/sq. ft.

 

SNOWFALL for LAST 24 HRS at OTHER STATIONS:
Nicks Valley at 4200 ft (in): 5″
Upper Tsaina at 1750 ft (in): 4″
Sugarloaf at 550 ft (in): 1″+Rain
SNOW DEPTH & WATER SURVEY (1/3/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  22.7″  4.7″
Milepost 18 27.9″ 5.9″
Milepost 29 Worthington Flats 44″ 9.9″
Milepost 37 Tsaina River bridge 33.8″ 5.6″
This survey is done the first week of each month.

Weather Quicklinks:

  • NWS forecast for Northeast Prince William Sound <here>
  • NOAA NWS spot forecast for Thompson Pass <here>
  • Thompson Pass RWIS weather station <here>
  • MP 30 Nicks (Happy) Valley weather station at 4200 feet <here> (scroll to Nicks Valley)
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map here>
  • Further weather resources <here>

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 VAC Forecasts.

Forecaster: Kevin Salys