Tuesday-Friday 2/21-24

Issued: Tue, Feb 21, 2017 at 8AM

Expires: Fri, Feb 24, 2017

The danger rating of Low danger doesn’t mean no danger. Expect new windslabs to form both with clear skies northerly outflow winds and with Wednesday’s few inches of new snow drifted by southerly onshore winds.

Remember to ALWAYS use travel techniques to your advantage. Don’t expose yourself to danger when you don’t have to. Ski/Highmark one at a time.

Above 2,500ft Low

1,800 to 2,500ft Low

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

TUESDAY WEDNESDAY THURSDAY & FRIDAY

DANGER SCALE

 

WIND SLAB:
Elevation:   Above 3000″
Aspect:   Lee to NE wind ( and S winds after Wednesday)
Terrain:   Near ridges, gullies, rollovers
Sensitivity:   Responsive
Distribution:   Specific
Likelihood (Human Triggered):   Possible
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

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Maritime (Coastal) Specific: 

Dust on crust below 2000 feet elevation from the February 14th rain. The snowpack is solid below the ~3000′ elevation rain line. There’s 4+ feet of new snow above that rain line, with wind drifting above treeline.

With springtime’s return of the sun and its trajectory rising ever higher above the horizon, there’s now enough solar radiation energy to release avalanches off sun baked slopes.

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

Maritime (Coastal) Specific: 

  • Numerous wet avalanches below the rain line (+-3000′) February  13-14 around the Port.
  • 2/18 Natural sluff avalanches (loose snow) observed on sunny south facing aspects from solar radiation.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  0 / 15
Ridgetop Wind Forecast (direction/mph):  NE / 20-40
Snowfall (in/water equivalent):  0″ / 0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  7 / NE  15 / NE
Max Wind Gust (mph) / Direction  16 / NE  35 / NE
Temperature Min / Max (*F)  17 / 29  -3 / 15

Weather Forecast:    Clear skies and increasing northerly outflow winds changing to clouds and a snowflake Wednesday with as much as four inches accumulation. Clearing skies Thursday with another cloud and snowflake possible Friday producing maybe an inch or two Saturday.

Additional Info & Media

SNOW HISTORY: Valdez 2/20 AM Thompson Pass 2/21 AM
24 Hour Snow / Water Equiv. 0”/0″ 0″ /0.0″
Storm Snow /Water Equiv. (2/17-2/18) 3.1” /0.2″ 3″ /0.3″
Current Snow Depth 51″ 48″
February Snow / Water Equiv. 44.2″ /4.5″ 42″ / 5.0″
Total Winter Snowfall / Water Equiv. 222.2″ /20.4” 281″ / 27.6″
Snowload in Valdez 78 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (2/21 AM)/STORM TOTAL (2/21)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 0″ / 0″
Upper Tsaina at 1750 ft (in): 0″ / 0″ / 0″
Sugarloaf at 550 ft (in): 0″/ 0″ / 0″
SNOW DEPTH & WATER SURVEY (2/1/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.5″  9.8″
Milepost 18 43.9″ 9.5″
Milepost 29 Worthington Flats 61.5″ 16″
Milepost 37 Tsaina River bridge 42.1″ 9.3″
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 Maritime Forecasts.
Pete Carter

Forecaster: Pete Carter