Choose routes that avoid windslab on steep slopes – if it sounds hollow, shoots crack, or collapses underfoot, you are on windslab. Talk about the consequences of the slope your group is committing to; is there a better option?
Above 2,500ft Considerable
1,800 to 2,500ft Moderate
Below 1,800ft Low
Degrees of Avalanche Danger ?
Elevation: Above 2000′
Aspect: Lee of ridges, gullies, ridgetops
Terrain: Upper elevation terrain exposed to wind
Likelihood (Human Triggered): Possible
Size: Small – Large
Danger Trend: Decreasing
Forecaster Confidence: Fair
Elevation: Above 2500′
Terrain: 35+ degrees steepness
Likelihood (Human Triggered): Unlikely
Size: Small – Large
Danger Trend: Decreasing
Forecaster Confidence: Poor
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: A skiff of snow fell Saturday evening. Sunday, north outflow wind is picking back up, so expect redistribution of loose snow, building fresh windslab near ridgetops and channeled areas. High to extreme winds Feb. 27 – Mar. 1 scoured exposed terrain and eroded into older snow layers. The snowpack depth varies widely due to these wind events scourly down to rock and heather, while just lee of ridges there are pockets of windslab meters deep.
The Feb. 23-27 storms totaled 10″ (30cm) on the pass. The Feb. 22 storm brought 4″ to Valdez and 6″ to the Pass and interior. North wind transported that new snow, and built windslab lee of ridges and gullies.
The combined effect of steady winds and sparse snow events has produced notable density and depth differences in the upper snowpack. The cold, clear weather between the 1/15 and 2/13 storms grew a weak layer that the next storm snow did not adhere to very well.
Due to that layer of facets (sugar snow), 2-6′ (60-180cm) beneath the surface, a persistent slab concern still exists. We’re still tracking the distribution above 2500′ and our recent snowpit tests are indicating this layer may no longer be widespread. The bottom line is that these persistent weak layers are stubborn to trigger, but due to depth, will have higher consequences if a rider, or riders, find the trigger point; be cautious near thinner areas near rocks and the edges of slabs.
Recent Avalanche Activity
There was a possible human triggered windslab avalanche Saturday in the Wortman’s area. No further details known at this time.
Feb.28 the rock bluffs near the Richardson Hwy hairpin at Milepost 23 popped off windslabs that covered the road.
Feb. 28 – Mar.1 Many naturally triggered windslab avalanches to size 2 released from ridgetops and crossloaded gullies in the mid and upper elevations. See observations page for details.
|WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:|
|Temperature Forecast (Min/Max *F):||0 / 20|
|Ridgetop Wind Forecast (direction/mph):||N /5-25|
|WIND & TEMPERATURE
PAST 24 hours
|Ferry Terminal||Thompson Pass|
|Average Wind Speed (mph) / Direction||9 / NE||30 / NE|
|Max Wind Gust (mph) / Direction||32 / NE||52 / NE|
|Temperature Min / Max (*F)||23 / 39||0 / 20|
Weather Forecast: Clear skies becoming cloudy Monday with the developing chance of a snowflake accumulating to a trace Tuesday. Increasing likelihood of real snow Thursday through the weekend. Temperatures warming from below zero Monday north of Thompson Pass into the teens during the forecast period as the northerly outflow winds are overrun with a more southerly flow.
Additional Info & Media
|SNOW HISTORY:||Valdez 3/4 AM||Thompson Pass 3/5 AM|
|24 Hour Snow / Water Equiv.||trace”/ 0″||0″ / 0″|
|Storm Snow /Water Equiv. (2/23-27)||~” / ~″||10″ / 0.9″|
|Current Snow Depth||30″||69″ wind scoured|
|March Snow / Water Equiv.||trace″ / 0″||trace″ / 0″|
|Total Winter Snowfall / Water Equiv.||112.95″ / 24.38”||323″ / 33″|
|Snowload in Valdez||47 lbs/sq. ft.|
|SNOW DEPTH & WATER SURVEY (3/4/2018)||Depth||Snow Water Equivalent|
|Milepost 2.5 Valdez||32.2″||9″|
|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.|
- Northeast Prince William Sound NWS Weather Forecast
- Middleton Island Radar for Valdez area
- GOES Alaska water vapor satellite loop
- NOAA NWS Recreational spot forecast for Thompson Pass
- Thompson Pass MP 25.7 RWIS weather station 2740′ (Mesowest)
- Valdez Marine Ferry Terminal weather station sea level
- Nicks Happy Valley above MP 30 weather station 4200′ (scroll to Nicks Valley)
- Upper Tsaina River Snotel near MP 32 1750′
- Sugarloaf Snotel 551′
- Above Valdez Glacier Cryosphere program weather station 6600′ <map here>
- Valdez Blueberry Weather Plot observations (scroll to bottom: Valdez City)
- More Mountain Weather resources for Alaska
- GFS 16 Day Model for Valdez
- Model Average Meteogram for Valdez
SNOW CLIMATE ZONES:
- Maritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
- Inter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
- Continental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).
Photo of Thompson Pass
Interactive Map of Valdez Forecast Areas w/ Many Resource Layers (Trevor Grams)
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.