Friday – Monday 3/31-4/3

Issued: Fri, Mar 31, 2017 at 8AM

Expires: Mon, Apr 03, 2017

Rising temperatures and more precipitation transitioning to rain will further test the new and old snow structure.

Expect conditions to change quickly as wet avalanche concerns will show themselves.

The beginning and end of a tour could have very different snow conditions.

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

Above 2,500ft Considerable

1,800 to 2,500ft Considerable

Below 1,800ft Considerable

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

FRIDAY SATURDAY SUNDAY & MONDAY

DANGER SCALE

 

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

WET LOOSE:
Elevation: <3000′
Aspect: All
Terrain: All
Sensitivity: Responsive
Distribution: Widespread
Likelihood (Human Triggered): Possible
Size: Small
Danger Trend: Increasing
Forecaster Confidence: Fair

WIND SLAB:
Elevation:
  Above 2500′
Aspect:
 various aspects
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:
   Increading
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: 

A few more inches of snow is accumulating on top of an upside down snowpack that has developed during a warm spell Wednesday, peaking in the high 30s down near the port and mid to high 20s near 3000′. 2+ feet of snow has been measured in the port and on Thompson Pass, with more likely in the upper elevations which is colder and dryer.

Expect loose wet snow activity to show itself today as temperatures warm and snow turns to rain.

On Thompson Pass (and likely elsewhere), 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 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.

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 on Wednesday.

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 have limited observations: please share if you have seen anything!!!

  • 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):  28 / 31
Ridgetop Wind Forecast (direction/mph):  SE / 15-30
Snowfall (in/water equivalent):  0-11″ / 0.96″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  2 / Var  17 / Var
Max Wind Gust (mph) / Direction  12 / SW  32 / ESE
Temperature Min / Max (*F)  31 / 35  29 / 28

Weather Forecast:  Snow intensity has picked up as the moisture moves in today which will transition to rain as the warm air mass associated mixes and settles into the area. Temperatures will near 40*F in the port today and freezing on Thompson Pass. Freezing line could climb as high as 2800′, but most moisture will remain confined to maritime side of the range due as the system will get hung up on the coastal topography. Temperatures will continue to rise through Saturday as the low moves NE into the Gulf of Alaska. Precipitation and clouds could break up Sunday to Monday morning before more moist flows get pushed onshore throughout next week.

Additional Info & Media

SNOW HISTORY: Valdez 3/31 AM Thompson Pass 3/31 AM
24 Hour Snow / Water Equiv.  2.3”/0.1″ 3″ /0.3″
Storm Snow /Water Equiv. (3/27-31)  15.9″ /?” 26″ /2.6″
Current Snow Depth 46.8″ 44″
March Snow / Water Equiv. 16.9″ /1.7″ 37″ / 3.0″
Total Winter Snowfall / Water Equiv. 239.8″ /22.6” 320″ / 30.7″
Snowload in Valdez 65.0 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (3/31 AM)/STORM TOTAL (3/27-31)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 4?” / 10?” / ?”
Upper Tsaina at 1750 ft (in): 1″ / 7″ / 1.0″
Sugarloaf at 550 ft (in): 1″/ 16″ / 1.8″
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.

Forecaster: Kevin Salys