Saturday – Tuesday 3/25-28

Issued: Sat, Mar 25, 2017 at 8AM

Expires: Tue, Mar 28, 2017

Gap winds continue to strip and load areas in the pass corridor and other main passes on the way to the gulf.  Other high elevations have reported significantly less wind and preserved snow.

Avoid freshly loaded areas and tiptoe around older firm slabs that have recently had scary collapses: see Avalanche Activity.

Join the VAC Basecamp FREE classes this weekend in the One Love Lot (MP 29.5). Check our Facebook page for more details!

 

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′
Aspect:  Lee to northerly and easterly winds
Terrain:   Near ridges, gullies, rollovers
Sensitivity:   Stubborn
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small – Large
Danger Trend:   Decreasing
Forecaster Confidence:   Fair

DRY LOOSE:
Elevation:   Above 2000′
Aspect:  All
Terrain:   Steep: >35*
Sensitivity:   Responsive
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small
Danger Trend:   Decreasing
Forecaster Confidence:   Good

WET LOOSE:
Elevation:   Below 3000′
Aspect:  Solar warmed southerlies
Terrain:   Steep, especially near rocks
Sensitivity:   Responsive after warmed
Distribution:   Specific
Likelihood (Human Triggered):   Possible
Size:   Small
Danger Trend:   Increasing with sun
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

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Maritime (Coastal) Specific: 

Do your best to evaluate and avoid old firm wind slabs that are harboring poor structure: strong over weak. There have been recently reported significant collapses (as large as whole basins whumphing) in areas on the northerly and easterly outreaches of our Inter-mountain zone, and into the Continental zone. Deep persistent slab problems are challenging to predict: have a lower probability of triggering, but consequences can be fatal if they do: large knife hard blocks that can easily crush!! Continue to monitor these layers as temperatures rise.

The last storm that hit us Sunday to Monday was enthusiastically welcomed after a parched spell of no precipitation. There was significant variation of new snow throughout the region. Cordova reported 8 inches at sea level Monday AM, with 2 feet at 1000′, while the town of Valdez received 2 inches with 1 foot at the pass, and trace amounts of snow at 56 Mile.

Since the storm, many available and willing testers reported numerous natural and skier triggered soft slab avalanches on Monday and Tuesday….mostly smaller in the destructive spectrum and deeper slabs the closer you get to Cordova.  North winds picked up Tuesday and have stripped and moved snow into firmer slabs in exposed terrain features. While the unconsolidated snow seems to be bonding quite well to older firm surfaces, the newer soft slabs formed on top of these weak storm snow crystals are more concerning, especially with warmer temperatures and direct solar influence. Evaluate the upper snow surfaces before committing. Older, pre-storm snow, has not seen any avalanche activity as of late.

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: 

  • *Reported March 24: Many siginifcant collapses (as large as whole basins whumphing) in areas on the northerly and easterly outreaches of our Inter-mountain zone, and into the Continental zone. Deep persistent problem RED FLAG!!!
  • Reported March 23: sizable natural release on SE aspect: possibly due to rising temps and solar warming
  • March 22: Natural D1 wind loaded soft slab releases on lee aspect to steep rollover below 27 Mile Peak near highway
  • March 20-21: widespread, both natural and skier triggered, soft slab activity reported 8-16cm thick propagating up to 150′; minor wind affect; many on NE aspects, smaller and stubborn to trigger

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  4 / 15
Ridgetop Wind Forecast (direction/mph):  NE / 20-40
Snowfall (in/water equivalent):  0″ / 0.0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  16 / E  30 / NE
Max Wind Gust (mph) / Direction  32 / SE  40 / NE
Temperature Min / Max (*F)  28 / 35  10 / 16

Weather Forecast: Enjoy the last sunny day for awhile as the shift to clouds and precipitation will begin tonight. Models are not on the same page, but more significant moisture seems that it could move this way Monday afternoon. The rest of the week is looking positive for some precipitation. Winds could pick up again Sunday.

Additional Info & Media

SNOW HISTORY: Valdez 3/25 AM Thompson Pass 3/21 AM
24 Hour Snow / Water Equiv.  0.0”/.00″ 3″ /0.2″?
Storm Snow /Water Equiv. (3/20)  0.0″ /.00″ 1″ /0.4″?
Current Snow Depth 37″ 42″
March Snow / Water Equiv. 0.8″ /.03″ 11″ / 0.4″
Total Winter Snowfall / Water Equiv. 223.7″ /20.8” 294″ / 28.1″
Snowload in Valdez 62.4 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (3/23 AM)/STORM TOTAL (3/20)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 2″ / 0.02″
Upper Tsaina at 1750 ft (in): 0″ / 0.1″ / 0.01″
Sugarloaf at 550 ft (in): 0″/ 0.1″ / 0.01″
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:

  • 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 Maritime Forecasts.

Forecaster: Kevin Salys