Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, December 17th, 2022 - 7:00AM
Expires
Sun, December 18th, 2022 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

Large persistent slabs 3 to 4 feet thick will be possible to human trigger and remotely trigger on all aspects, at all elevations on slopes steeper than 30º.

Dry loose sluffs will be easy to human trigger on any slope steeper than 40º.

Natural avalanches are unlikely.

Avalanche behavior will be difficult to predict. Use safe travel protocols to increase your margin of safety.

Numerous natural avalanches occurred 12/13 and 12/15 that failed at the ground.

After a long week with significant precipitation, we are looking at a strong ridge of high pressure that will dominate the weather for the next several days.

Special Announcements

Update from DOT: Road will remain closed at least through the weekend at MP 14 HATCHER PASS RD (PALMER-FISHHOOK). Gold Mint Parking Lot is open.

Come join HPAC on January 21st at Bearpaw brewing for our annual beer release party. Support HPAC, enjoy a cold beverage, and meet the forecasters.

Sign up for our newsletter here for the latest on this event and future HPAC happenings.

Sat, December 17th, 2022
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2,500'-3,500'
2 - Moderate
Avalanche risk
Low Elevation
Below 2,500'
2 - Moderate
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

Numerous large to very large natural avalanches were observed on 12/13 and 12/15.

Numerous large naturals, Stairstep and Punkspines 12.13 and 12.15 W/NW 3300′

 

Natural, mid-slope Arkose ridge 12.15 SW 3500′

 

Naturals, Government 12.15 NE 3500′

 

Natural, Wimp Bowl 12.15 NE 3800′

 

Natural, Marmot 12.15 S 3500′

 

Naturals , Arkose ridge 12/13-15

 

Numerous naturals on Government NE 4000 12.13 and 12.15

 

 

Natural, Hatch 12.13 SE 4500′

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

Stability is slowly improving, however, this avalanche problem will continue to linger. Each time the snowpack is freshly loaded natural avalanche activity is likely.  We are dealing with a tricky and untrustworthy snowpack. We saw evidence of this in the last storm from 12/11 to 12/15.

Today avalanche behavior will be difficult to predict. Human triggering large avalanches 3 to 4 feet deep will be possible on all aspects, at all elevations, on slopes steeper than 30º.

Natural avalanches are unlikely.

Remotely triggering a large avalanche will be the biggest concern of the day.

12.13 Punk Spines NW 4000′

 

Natural, end of Frostbite ridge 12.15 NE 3400′

Our biggest concern continues to be the weak, basal facets at the bottom of the snowpack.

The good news is that triggering an avalanche is becoming more difficult. The bad news is that it is still possible to trigger a large, high consequence slab avalanche.

We are entering a low probability, high consequence senario where safe travel protocol will be integral to avoiding getting caught in an avalanche.

If you head into avalanche terrain today, utilize strict safety travel protocols, travel one at a time from safe zone to safe zone, only have one person on slope at a time, ensure all members of your party are carrying and know how to use beacons, shovels and probes, and avoid slopes with terrain traps.

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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

Several loose dry avalanches occurred during and after the 12/11-15 storm.

The most recent 9″ of new snow that accumulated on 12/15 is losing density thanks to cold temps which increases the likelihood of triggering this avalanche type.

Small to large loose dry sluffs will be likely to human trigger on any slope steeper than 40º.

Getting caught up in a loose dry avalanche in steep terrain may sweep you into terrain traps compounding the overall hazard.

Naturals , Skyscraper 12.15 SE/E 4000′ photo: Dan Amyot

We will be adjusting our travel protocol to mitigate for this hazard. Loose snow will not bond well to the new drizzle crust, and will be easy to trigger on slopes 40º and steeper.

 

Weather
Sat, December 17th, 2022

From 12/11-12/15 Hatcher Pass received approximately 38 inches of snow and 3.6 inches of SWE.

 

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.

Observations
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