Saturday-Tuesday 3/11-14

Issued: Sat, Mar 11, 2017 at 8AM

Expires: Tue, Mar 14, 2017

Citizen Science Opportunity in Thompson Pass: March 18, 2017: 9:30am at DOT Camp (MP 27).  Join VAC forecasters, staff, and volunteers in measuring the snow cover throughout Thompson Pass. Learn more at www.nasacso.org or at the Fat Mermaid March 15 & 16th 5:30pm.

Dramatic variability, even within one single slope, should lead to conservative travel in avalanche terrain.

Evaluate recently formed wind slab and how it is bonding to underlying layers….steep and unsupported terrain is more suspect.

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

SATURDAY SUNDAY MONDAY & TUESDAY

DANGER SCALE

 

WIND SLAB:
Elevation:   Above 2000′
Aspect:  Lee to northerly winds
Terrain:   Near ridges, gullies, rollovers
Sensitivity: Stubborn
Distribution:   Specific
Likelihood (Human Triggered): Unlikely
Size:   Small – Large
Danger Trend:   Decreasing
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: 

It has been over 2 weeks since a snowflake has fallen from the sky and 11 days since the strong north winds started wreaking havoc on our snowpack. These extreme winds, that peaked near 90 mph, have scoured deep into older snow and drifted snow into low lying gullies, trees, crevasses and rollovers.  Many natural wind slab avalanches released throughout our region while few human triggered were reported, likely due to the inhospitable conditions. Wind affected areas have knife hard windslab, sastrugi, rain/melt-freeze crusts and wind scoured bare ground. The main concern is windslab over ice crust, buried surface hoar and near surface facets. Steep southerlies in the lower elevations are melting out to bare ground.

Steep, low elevation southerlies melting out.

Thompson Pass gap winds still scouring into the snowpack.

Rain Crust from mid Feb.

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: 

  • No recent avalanche activity seen, but some recently seen wind slabs (likely occured during Mar. 2-3 wind event) had scoured/released to ground near the 3000′ elevation on varying aspects.

Wind slab to ground west of Meteorite. NE aspect at ~3000′

Scouring/releases to ground near East Peak. SE aspect at ~3500′

  • Mar. 2: More natural wind slabs to size 2 pulling off steep ridgelines and rollovers in terrain exposed to strong northerly outflow wind.

Wind slab releases above the airport

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  3 / 11
Ridgetop Wind Forecast (direction/mph):  NE / 15-30
Snowfall (in/water equivalent):  0.0″ / 0.0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  11 / NE  25 / NE
Max Wind Gust (mph) / Direction  29 / NE  38 / NE
Temperature Min / Max (*F)  17 / 27  -2 / 10

Weather Forecast:   Sunshine and a less exposure to ridgetop winds should be taken advantage of this weekend. Like yesterday, it seems the bulk of the cold, outflow winds will be channeling over lower passes and down major drainages out to sea. A weak low pressure system deflected up the gulf coast will likely bring increasing winds Sunday night and clouds late Monday. There is hope that a brief dusting of snow will get squeezed out of the atmosphere mid-day Tuesday and again Thursday afternoon….depending on how the low moves through the Gulf of Alaska.

Additional Info & Media

SNOW HISTORY: Valdez 3/10 AM Thompson Pass 3/10 AM
24 Hour Snow / Water Equiv.  0”/0″ 0″ /0″
Storm Snow /Water Equiv. (2/23)  0″ /0″ 2″ /0.1″
Current Snow Depth 37″ 39″
March Snow / Water Equiv. 0″ /0″ 0″ / 0″
Total Winter Snowfall / Water Equiv. 222.8″ /20.9” 283″ / 27.7″
Snowload in Valdez ~ lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (3/10 AM)/STORM TOTAL (3/10)/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 (2/28/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.8″  12″
Milepost 18 42.7″ 11.5″
Milepost 29 Worthington Flats 63.6″ 18.6″
Milepost 37 Tsaina River bridge 49.3″ 12.5″
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.

Forecaster: Kevin Salys