Saturday-Tuesday 3/4-3/7

Issued: Sat, Mar 04, 2017 at 8AM

Expires: Tue, Mar 07, 2017

 

Give wind-loaded terrain features time to bond and test small features before going big.

New wind slabs can release much larger and deeper than expected….leading to consequential avalanches with firm and powerful blocks of snow.

 

Above 2,500ft Moderate

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

SATURDAY SUNDAY MONDAY & TUESDAY

DANGER SCALE

 

WIND SLAB:
Elevation:   All
Aspect:  Lee to northerly winds
Terrain:   Near ridges, gullies, rollovers
Sensitivity:   Responsive
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small – Large
Danger Trend:   Decreasing slowly
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: 

Today and early tomorrow will provide a brief respite from strong outflow winds forcing their way over passes and ridgelines from the north. They will likely pick up again Sunday afternoon and into Monday. Extreme winds that peaked near 90 mph scoured deep into older snow and drift 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. Expect firm and variable conditions with exposed old crusts, wind board and sastrugi dominating the environment. Extra effort will be necessary to seek out the wind protected nooks that harbor soft snow. Be wary along corniced and loaded ridgelines, convex rollovers and steep gully walls. Wind slab needs time to bond to underlying snow and can trigger very large and unpredictable avalanches.

There also has been recently reported findings of widespread buried surface hoard and near surface facets within the maritime zone….something that could easily be extending into all zones into the interior. No details on how sensitive they were, but worthy of noting and to keep tabs on.

Outflow gap winds hitting 68mph

 

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: 

  • 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

Windslab crown below Moonlight Basin

  • Feb. 28: Commonly seen during strong outflow winds, natural avalanches to D2 have pulled off the rollovers on the south side of Odyssey just above the hairpin.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -2 / 7
Ridgetop Wind Forecast (direction/mph):  NE / 20-40
Snowfall (in/water equivalent):  0.0″ / 0.0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  14 / NE  35 / NE
Max Wind Gust (mph) / Direction  68 / NE  93 / NE
Temperature Min / Max (*F)  19 / 27  2 / 8

Weather Forecast:     A drop in wind will be enjoyed until Sunday afternoon, when the first of two low pressure disturbances will ramp up the northerly outflow gusts. They shouldn’t be as intense as Thur-Fri, but worthy nonetheless. This is also usher in a slight drop in temperatures as arctic air gets pulled south. No clouds or moisture in sight….more high pressure blocking likely through the week.

Additional Info & Media

SNOW HISTORY: Valdez 3/5 AM Thompson Pass 3/4 AM
24 Hour Snow / Water Equiv.  0”/0″ 0″ /0″
Storm Snow /Water Equiv. (2/23)  1” /0.05″ 2″ /0.1″
Current Snow Depth 41″ 42″
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 (3/4 AM)/STORM TOTAL (3/4)/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