Wednesday-Saturday 1/18-1/21

Issued: Wed, Jan 18, 2017 at 8AM

Expires: Sat, Jan 21, 2017

Choose lower angle slopes to play on today. Pay attention to windlips and rollovers to know where the windslab is building. Gullies will most likely be crossloaded, gathering deep slab that could get moving fast in steep terrain.

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

WEDNESDAY THURSDAY FRIDAY & SATURDAY

DANGER SCALE

WIND SLAB:
Elevation:
 Above 1800′
Aspect: South and west, but all exposed to wind have been loaded in the last week
Terrain:
Slopes steeper than 30 degrees, loaded by NE wind
Sensitivity:
 Responsive
Distribution:
 
Specific
Likelihood (Human Triggered): 
Likely
Size:
 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: Coverage doesn’t look much better than before the Jan.13-17 storm that laid down 54 inches of snow. Both south and north wind has stripped and redistributed what fell. Now, strong northeast wind is again wrecking havoc: expect windslab depths to 3 feet or more on lee features. The cold temperatures, near or below zero F, at Thompson Pass and inland will decrease the bonding strength of fresh windslab and storm snow to old surfaces.

In wind protected areas, the storm snow is settling and has formed a soft slab. Skiers reported large whumphs near the Worthington Glacier, reminding us we cannot fully trust this snowpack yet, especially inland of Thompson Pass. Structurally the weak sugar snow lower in the pack is precariously holding up top heavy mid and upper slab layers.

The spooky large avalanche west of Milepost 33, south aspect about 4000′, is evidence that increased load can trigger and cause a step down to deep old presistent weak layers.

Find more photos and observations at the bottom of the page. Sharing your observations helps others make informed decisions.

Recent Avalanche Activity

With a few short windows of visibility Tuesday, surprisingly not much avalanche activity was observed. The increase in temperature during the storm seemed to glue on what wasn’t blown away. Please share what you see.

coastal-zone-iconMaritime (Coastal):

intermountain-zone-iconInter-Mountain (Transitional):  

interior-zone-iconContinental (Interior):

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -12 / 3
Ridgetop Wind Forecast (direction/mph): NE / 12-42
Snowfall (in):  0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   10/ var  30 / var
Max Wind Gust (mph) / Direction  18 / NE  55 / NE
Temperature Min / Max (*F)  18 / 24  -2 / 12

Weather Forecast: Windy and cold Wednesday and Thursday. With a mass of cold arctic air, north outflow wind is ramping up, only to die down by Friday when another low pressure will move in with clouds. Expect flurries by Saturday.

Additional Info & Media

SNOW HISTORY: Valdez 1/18 AM Thompson Pass 1/18 AM
24 Hour Snow / Water Equiv. trace” /0.03” 1″ /0.01″
Storm Snow /Water Equiv. (1/13-1/17) 46.41” /3.22″ 54″ /4.2″
Current Snow Depth 44.07″ 36″ (wind scoured)
January Snow / Water Equiv. 46.41″ /3.22″ 54″ / 4.2″
Total Winter Snowfall / Water Equiv. 44.85″ / 13.04” 197″ / 18.6″
Snowload in Valdez 27.56 lbs/sq. ft.

img_20161228_130954img_20161228_130730

Photos of our new Nicks Valley Weather Station Python to the east, Berlin Wall to the west.

SNOWFALL for LAST 24 HRS at OTHER STATIONS:
Nicks Valley at 4200 ft (in): ~5″
Upper Tsaina at 1750 ft (in): ~3″
Sugarloaf at 550 ft (in): ~3″
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.
Pete Carter

Forecaster: Pete Carter