Monday-Thursday 3/19-3/22

Issued: Mon, Mar 19, 2018 at 8AM

Expires: Thu, Mar 22, 2018

Above 2,500ft Moderate

1,800 to 2,500ft Moderate

Below 1,800ft Moderate

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Monday Tuesday Wednesday
& Thursday

DANGER SCALE

 

WIND SLAB:
Elevation:   Above 1000′
Aspect:   Lee of ridges, gullies, ridgetops
Terrain:   All terrain exposed to wind, particularly north winds starting Tuesday
Sensitivity:   Responsive
Distribution:   Specific
Likelihood (Human Triggered):   Likely as soon as the north wind howls
Size:   Small – Large
Danger Trend:   Increasing until winds peak Wednesday night
Forecaster Confidence:    Good

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:     There’s 1-2 feet of soft snow available for wind transport with strong northerly outflow winds expected to pick up Monday afternoon. Winds are forecast to exceed 70 mph Tuesday and Wednesday (hurricane force).

Excellent Observations <here> thanks to Gareth, Trevor, and Alex.

Several human triggered whumpfs occurred above 2500′ elevation NW aspect above Milepost 34 where tests of the weakness produced an ECTP 13 Q1 result.

Recent Avalanche Activity

March 17: D2 Wind slab, upper elevation, north aspect inter-mountain snow climate zone, accidental human triggered one foot deep, 30 feet wide, ran 450 feet.
March 16: D1 Storm slab, intentional human triggered.
March 14: D2 Storm slab, intentional human triggered.

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F): 12 / 28
Ridgetop Wind Forecast (direction/mph): S-N /5-25
Snowfall (in):  1-3″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  0 / ~   15 / variable
Max Wind Gust (mph) / Direction  4 / N  35 / NE
Temperature Min / Max (*F)  32 / 38  22 / 31

Weather Forecast:    Flurries producing a couple more inches of snow Monday.  The skies will clear Tuesday bringing hurricane force northerly outflow winds and stunningly beautiful vistas for the remainder of the forecast period.

Additional Info & Media

SNOW HISTORY: Valdez 3/18 AM Thompson Pass 3/19 AM
24 Hour Snow / Water Equiv. 0”/ 0.03″ 3″ / 0.3″
Storm Snow /Water Equiv. (3/9-14) 19” / 0.41″ 40″ / 1.5″
Current Snow Depth 33″ 84″
March Snow / Water Equiv. 20″ / 2.56″ 47″ / 3.3″
Total Winter Snowfall / Water Equiv. 132.54″ / 26.93” 370″ / 36.3″
Snowload in Valdez 55 lbs/sq. ft.

 

SNOW DEPTH & WATER SURVEY (3/4/2018) Depth Snow Water Equivalent
Milepost 2.5 Valdez  32.2″  9″
Milepost 18 42″ 11″
Milepost 29 Worthington Flats 62.4″ 21.2″
Milepost 37 Tsaina River bridge 58.4″ 14.2″
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 Continental Forecasts, Intermountain Forecasts, Maritime Forecasts.
Pete Carter

Forecaster: Pete Carter