Tuesday-Friday 4/4-4/7

Issued: Tue, Apr 04, 2017 at 8AM

Expires: Fri, Apr 07, 2017

Friday April 14 bon fire: VAC Full Moon FUNraiser with Acoustic Avalanche at the Tsaina Lodge

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

TUESDAY WEDNESDAY THURSDAY & FRIDAY

DANGER SCALE

 

WIND SLAB:
Elevation:
  Above 2500′
Aspect:
  aspects lee of south-southwest storm wind
Terrain:
shallow snowpack near ridges, rollovers, gullies with facets underneath
Sensitivity:
   Responsive
Distribution:
   Fresh windslab where sits over facets or hasn’t yet bonded.
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

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Maritime (Coastal) Specific: 

With the last two days of good lighting Thompson Pass has had many great slope tests from snowmachiners, boarders & skiers. Small (D1) wind slabs were triggered in the inter-mountain zone. This warrants concern for unsupported wind loaded slopes in upper elevation ridgetops, gullies and convexities in the maritime side. The danger trend is increasing with the new snow from last night.

On Thompson Pass a couple  new melt-freeze crusts have formed up to ~2600′. A thinner (1″, 4F) crust near the surface sandwiched several inches of soft snow between a thicker (~3″; 1F+) melt freeze crust almost a foot down. Hand shear testing Friday demonstrated poor crust bonding with very easy results when isolating columns. Propagation was supported at ~2400′ on Thompson Pass on Thursday, when a large collapse occurred of the new storm snow (thick crust and everything above) resting on buried facets below. In areas where the facets did not reside, bonding of new snow was good.

Evaluation of the snowpack down near Cracked Ice Friday showed much better bonding and no propagation. See recent observation.

Higher elevations exposed to wind have fresh wind slab formation that has been bonding well to underlying snow thus far (Q3 w/ steps), unless it is sitting on a persistently weak grain (old facets). A small collapse of newly blown in shallow slab on rocks occurred at ~3000′ on Thompson Pass on a southerly aspect.

Human triggered avalanches were reported on the road run earlier this week and slab and wet loose snow was moving on very steep slopes around the port during the storm.

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 31: Many small (D1) loose wet avalanches around the port and in Keystone Canyon.
  • March 29: 0-1000′ elev. below Comstock: up to 18″ of heavy storm snow was shifting and sliding under foot in steeps with friction: propagation limited.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  30 / 36
Ridgetop Wind Forecast (direction/mph):  NE / 2-15
Snowfall (in/water equivalent):  1″ / 0.25″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  5 / NE  7 / NE
Max Wind Gust (mph) / Direction  15 / ENE  17 / SE
Temperature Min / Max (*F)  31 / 42  18 / 30

Weather Forecast:   More snow possible through the week.  Clouds will drift through with 1/2 inch water equivalent through Friday. The freezing level dropping to surface, with daytime max near 2500′. Moderate south to east wind.

Additional Info & Media

SNOW HISTORY: Valdez 4/4 AM Thompson Pass 4/4 AM
24 Hour Snow / Water Equiv.  0”/0.04″ 2″ /0.2″
Storm Snow /Water Equiv. (3/27-4/3)  16.9″ /4.1″ 23″ /2.3″
Current Snow Depth 43″ 45″
April Snow / Water Equiv. ~″ /0.47″ 8″ / 0.8″
Total Winter Snowfall / Water Equiv. 240.8″ /23.7” 327″ / 31.4″
Snowload in Valdez 65.0 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (4/4 AM)/STORM TOTAL (3/27-4/2)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 1″ / ~16″ / ?”
Upper Tsaina at 1750 ft (in): 1″ / ?” / 1.2+”
Sugarloaf at 550 ft (in): .5″/ 20+rain” / 2.8″
SNOW DEPTH & WATER SURVEY (4/2/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.9″  11.9″
Milepost 18 40″ 11.9″
Milepost 29 Worthington Flats 62.2″ 19.6″
Milepost 37 Tsaina River bridge 46.3″ 12.5″
This survey is done the first week of each month.

Weather Quicklinks:

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: Bobby Lieberman