Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, December 31st, 2022 - 7:00AM
Expires
Sun, January 1st, 2023 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

The avalanche danger is LOW today at all elevations and on all aspects.

Natural and human triggered avalanches will be unlikely.

A remote possibility exists for triggering a large persistent slab in isolated areas or extreme terrain.

Although the avalanche danger is low, the likelihood of injuring yourself while navigating sastrugi, wind slabs, firm surfaces, and breakable crust is high, especially on the descent. This will be the biggest hazard of the day!

Sledding, skate skiing, or snowmachining will most likely bring more joy to your life today.

We are looking forward to more desirable conditions and new snow with the New Year!

Special Announcements

Join HPAC on Saturday, Jan 21st at Bearpaw Brewing to celebrate the return of the HPAC Square Pow IPA. Stop by between 11AM-8PM, at the “Big Bear” location at 240 E Railroad Ave. Portions of the proceeds will be donated to HPAC and food will be available.

Sat, December 31st, 2022
Upper Elevation
Above 3,500'
1 - Low
Avalanche risk
Mid Elevation
2,500'-3,500'
1 - Low
Avalanche risk
Low Elevation
Below 2,500'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches

No recent avalanches have been observed or reported since 12/23.

Recent obs here.

Dec 24 forecast with pics of avalanches here.

 

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Even though the overall hazard for persistent slab avalanche is rated at LOW, it is still worth some discussion.

Low hazard does not mean no hazard, and we expect there to be isolated locations and extreme terrain where human triggering a persistent slab may still be possible. Given the poor structure of the snowpack, it’s impossible to completely rule out any possibility of triggering an avalanche.

These locations will continue to be hard to identify. Locations with a shallower snowpack, on southeast to west aspects, less than a meter deep, combined with a large load such as a snowmachine will have a higher likelihood of triggering an avalanche.

In general, the structure at the bottom of the snowpack near the ground is improving.  We are getting little to no propagation in our pits. We have not seen an avalanche since December 23rd. We have not observed any red flags in over a week.

12.24 Sastrugi and anti-tracks from several days of wind on lower Marmot looking across at Skyscraper

Snow surfaces are highly variable with numerous types of wind effect including thick supportable wind slab, thin breakable wind slab, soft deposited snow, sastrugi and anti tracks. These conditions will make any descent quite challenging. The snowpack depth varies from 10″ in scoured locations up to 6 feet deep on leeward aspects.

12.30 Conditions are highly variable in many locations. This picture is taken on Presidents Ridge.

 

12.30 Looking across at Arkose ridge and the Punk spines. This photo shows old crowns and a significant amount of terrain scoured to the ground from last week’s wind.

 

Sidewall pit profile on Presidents ridge. Despite how awful this looks, consider this. Facets under the wind slab are rounding, the rain crust is brittle and deteriorating, and basal facets are rounding and moist. The snowpack is graining strength slowly.

 

Very few people have been out recreating either because they know the conditions are harrowing or they were trapped with a snow berm blocking their driveway for several days. Either way, if you get out, we’d love to hear from you. Send us an observation!

Weather
Sat, December 31st, 2022

WINTER WEATHER ADVISORY

WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 3 AM SUNDAY TO MIDNIGHT AKST SUNDAY NIGHT

Hatcher Pass is expected to receive little to no precipitation through this evening due to the southeasterly flow aloft, but will pick up late tonight into Sunday morning. Precipitation will fall as freezing rain or a wintery mix due to warmer air. Additionally, easterly winds in the 20 to 30 mph range are possible.

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NWS AVG Forecast here.


NWS point forecast here.


Marmot Weather Station here.


Independence Mine Snotel here.


State Parks Snow Report and Motorized Access information here.



			

		

		
	

		
	

		

			

				
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