Sunday – Wednesday 3/26-29

Issued: Sun, Mar 26, 2017 at 8AM

Expires: Wed, Mar 29, 2017

Avalanche Center Tsaina Lodge Spring Full Moon Bon Fire FUNraiser

Friday April 14 presenting Acoustic Avalanche

 

Above 2,500ft Moderate

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 3000′
Aspect:  Lee to northerly and easterly winds
Terrain:   Near ridges, gullies, rollovers
Sensitivity:   Stubborn
Distribution:   Specific
Likelihood (Human Triggered):   Possible
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: 

Poor structure of the snowpack, strong snow sitting over weak snow, remain the concern, both newer windslabs acros the maritime snow climate zone, and whole basins whumphing in areas on the northerly and easterly outreaches of our inter-mountain zone, and into the continental zone. Deep persistent slab problems are challenging to predict with a lower probability of triggering, but with serious consequences.

Last week’s series of convective storms across the region deposited significant variation of new snow throughout the region. Cordova reported 8 inches at sea level and 2 feet above 1000′. Valdez received 2 inches with 1 foot at Thompson Pass and in the upper elevations of the maritime snow climate zone. Kenny Lake has recieved an inch or two almost daily through the past week.

There’ve been numerous natural and human triggered soft slab avalanches over the past week, mostly D1-2. However, with increasing solar radiation, >D2 natural releases are observed off E-S-W aspects.

With the change in the weather and significant snowfall increasingly possible, the recrystalized near surface faceting above 4000′ elevation will, once buried, become the weak layer of concern.

The snowpack at sea level and on south aspects up to 3000′ elevation have been ablating dramatically.

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: 

  • March 25 repports of upper elevation (>4500′ elevation) human triggered windslabs to a foot thick releasing off steep slopes.
  • *Reported March 24: Many siginifcant collapses (as large as whole basins whumphing) in areas on the northerly and easterly outreaches of our Inter-mountain zone, and into the Continental zone. Deep persistent problem RED FLAG!!!
  • Reported March 23: sizable natural release on SE aspect: possibly due to rising temps and solar warming
  • March 22: Natural D1 wind loaded soft slab releases on lee aspect to steep rollover below 27 Mile Peak near highway
  • March 20-21: widespread, both natural and skier triggered, soft slab activity reported 8-16cm thick propagating up to 150′; minor wind affect; many on NE aspects, smaller and stubborn to trigger

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  10 / 20
Ridgetop Wind Forecast (direction/mph):  NE / 20-40
Snowfall (in/water equivalent):  1″ / 0.01″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  16 / E  26 / NE
Max Wind Gust (mph) / Direction  32 / SE  35 / NE
Temperature Min / Max (*F)  28 / 35  5 / 16

Weather Forecast:   Clouds with a chance of producing a snowflake Sunday and Monday, with the snowflakes Tuesday steadily piling up to a total accumulation of a foot or more by the end of the week. Outflow winds continuing until mid-week onshore winds. Seasonal temperatures.

Additional Info & Media

SNOW HISTORY: Valdez 3/25 AM Thompson Pass 3/27 AM
24 Hour Snow / Water Equiv.  0.0”/.00″ 2″ /0.2″
Storm Snow /Water Equiv. (3/27)  0.0″ /.00″ 2″ /0.2″
Current Snow Depth 37″ 36″
March Snow / Water Equiv. 0.8″ /.03″ 13″ / 0.6″
Total Winter Snowfall / Water Equiv. 223.7″ /20.8” 296″ / 28.3″
Snowload in Valdez 62.4 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (3/26 AM)/STORM TOTAL (3/26)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 0″ / 0.0″
Upper Tsaina at 1750 ft (in): 0″ / 0″ / 0.0″
Sugarloaf at 550 ft (in): 0″/ 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.
Pete Carter

Forecaster: Pete Carter