Sunday-Wednesday 4/2-5/17

Issued: Sun, Apr 02, 2017 at 8AM

Expires: Wed, Apr 05, 2017

The storm is clearing. Cautious routefinding and conservative decision-making will allow you to test how the new snow is reacting.

Dr. Cullen is giving a presentation on Backcountry Injuries this afternoon Sunday April 2 at the Fat Mermaid 4-6pm.

Friday April 14: VAC Full Moon FUNraiser with Acoustic Avalanche @  Tsaina Lodge

Above 2,500ft Considerable

1,800 to 2,500ft Moderate

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

SUNDAY MONDAY TUESDAY & WEDNESDAY

DANGER SCALE

 

STORM SLAB:
Elevation: All
Aspect: All
Terrain: All
Sensitivity: Responsive
Distribution: Widespread
Likelihood (Human Triggered): Likely
Size: Small – Large
Danger Trend: Decreasing
Forecaster Confidence: Good

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:
   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: 

Snow up high and rain down low added stress and weight to our snowpack. Better visibility will allow for investigation of how the storm snow is settling into it’s new home.

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 will likely 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: 

Poor visibility during the storm has limited observations. Today’s clearing will give us a look around.

  • 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.
  • March 28: human triggered avalanches on the road run.
  • March 25: reports of upper elevation (>4500′ elevation) human triggered windslabs to a foot thick releasing off steep slopes.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  24 / 29
Ridgetop Wind Forecast (direction/mph):  SSE / 12-28
Snowfall (in/water equivalent):  0-5″ / 0.35″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  5 / Variable  15 / SE
Max Wind Gust (mph) / Direction  20 / WSW  30 / SE
Temperature Min / Max (*F)  34 / 40  24 / 32

Weather Forecast:  With the low pressure system moving past, clearing skies will give us a chance to look around today. A bit more snow possible through the week. Dribs and drabs of cloud will drift through with 1/2 inch water equivalent through Friday. The freezing level id dropping to surface, with daytime max near 2500′. Moderate south to east wind.

Additional Info & Media

SNOW HISTORY: Valdez 4/3 AM Thompson Pass 4/3 AM
24 Hour Snow / Water Equiv.  0”/0.05″ 1″ /0.1″
Storm Snow /Water Equiv. (3/27-3/3)  16.9″ /4.1″ 23″ /2.3″
Current Snow Depth 43″ 45″
April Snow / Water Equiv. ~″ /0.47″ 6″ / 0.6″
Total Winter Snowfall / Water Equiv. 240.8″ /23.7” 325″ / 31.2″
Snowload in Valdez 65.0 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (4/2 AM)/STORM TOTAL (3/27-4/2)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0.1″ / ~16″ / ?”
Upper Tsaina at 1750 ft (in): rain” / ?” / 1.2+”
Sugarloaf at 550 ft (in): rain”/ 20+rain” / 2.8″
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:

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.
Sarah Carter

Forecaster: Sarah Carter