Saturday-Tuesday 2/11-14

Issued: Sat, Feb 11, 2017 at 8AM

Expires: Tue, Feb 14, 2017

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 2000 feet elevation
Aspect:
 South and west 
Terrain: 
  All terrain exposed to wind
Sensitivity:
   Responsive
Distribution: 
Specific
Likelihood (Human Triggered): 
Possible
Size: 
Small – Large
Danger Trend:
   Increasing 
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:

intermountain-zone-iconInter-Mountain (Transitional) Specific: 

Near ridgetops and wind channeled terrain, the north wind has transported the unconsolidated surface snow and formed windslab on leeward slopes.  Much of the high ground is wind affected and scoured. Many pockets of hard windslab naturally popped off rollovers and steep gully ways last weekend with little to no new activity since. Poke around to see how the windslab is bonded to layers below.  Soft snow is still found in wind protected valleys. Some surface hoar observed.

Generally:

It is a variety pack out there….snow”pack” that is….of the not so desirable type….where you yearn for only one of the options in the mix (soft snow), but the less desirable options dominate the package. If one wanders out right now you will find it all: rocks, tundra, exposed lake ice (Odyssey), sastrugi, wind board, decomposing snow, near surface facets, surface hoar, and even melt-freeze crusts. It all depends on where you go, but most of the upper elevations have been wind hammered and require reserved travel speeds.  Things are pretty thin overall, a lot of rock showing and very old, early season layers continue to resurface.

Prior to the 3 inches last night, the last snowfall ended more than a week ago, Jan.31. Since then, the storm snow has settled and bonded to snow beneath fairly well. The north wind has moved and textured much of the snow.  Feb.1-5 was the return of sun affect: solar radiation and warm daytime temperatures triggered roller balls and loose avalanches on southerly aspects, sometimes trenching to the ground near town. It was a dramatic shift from early season to more spring-like snow conditions that brought above freezing temperatures all the way up to Thompson Pass.

Things cooled off significantly and now slightly warmed with this front. Very light, dry flakes have dusted the mountains.

While out in the colder side of the inter-mountain zone Wed, Feb 8th, I was able to get my first propagation in an ECT in awhile….2 results actually. This is at nearly 5000′ on a SE aspect below Max Low…~MP 33. ECTP13 RP in the decomposing fragments below wind board (down 20cm) and ECTP30 SC in the weak basal 2-4mm depth hoar at the ground. This demonstrates the continued weak structure at the bottom of our pack and stirs up the question: What forces and circumstance could fail this weak and stubborn layer, taking the whole snowpack with it? Keep an eye on it, especially as temperatures warm this spring.

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

intermountain-zone-iconInter-Mountain (Transitional) Specific:  

  • No new observations reported.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -5 / 10
Ridgetop Wind Forecast (direction/mph): NE / 30-45
Snowfall (in):  0-2
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   8 / NE  28 / NE
Max Wind Gust (mph) / Direction  20 / NE  45 / NE
Temperature Min / Max (*F)  18 / 23  -5 / 10

Weather Forecast:    Starting out Saturday with overcast and flat light with the sun poking out Saturday afternoon. Cold and windy with significant wind chill where exposed. Snowflakes Sunday accumuating above the freezing level to a foot Monday, another foot and a half Tuesday, for a storm total of three and a half feet by the end of Thursday. Good chance of rain in town Monday and Tuesday.

Additional Info & Media

SNOW HISTORY: Valdez 2/9 AM Thompson Pass 2/9 AM
24 Hour Snow / Water Equiv. 0.4”/Trace” 3″ /0.2″
Storm Snow /Water Equiv. (2/8-9) 0.4” /Trace″ 3″ /0.2″
Current Snow Depth 37.4″ 39″
February Snow / Water Equiv. 3.1″ /0.2″ 6″ / 0.4″
Total Winter Snowfall / Water Equiv. 181″ / 16.1” 245″ / 23.1″
Snowload in Valdez 50 lbs/sq. ft.

 

SNOWFALL for LAST 24 HRS at OTHER STATIONS:
Nicks Valley at 4200 ft (in): Trace?”
Upper Tsaina at 1750 ft (in): Trace?”
Sugarloaf at 550 ft (in): Trace?”
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 Intermountain Forecasts.
Pete Carter

Forecaster: Pete Carter