Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, February 18th, 2022 - 7:00AM
Expires
Sat, February 19th, 2022 - 7:00AM
Forecaster
Allie Barker
Avalanche Warning
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line

The Valentines Week Storm has not let us down. In the past 24 hours we have received another 3″ of water and approximately 16-20″ of snow. This brings our storm totals to 6″SWE and 40″ of snow approximately.

Avalanche danger will remain HIGH today. Large to very large human triggered avalanches are very likely on all aspects at all elevations on slopes above 30º. Naturals avalanches are likely. 

The road will remain closed at mile 11 through the weekend due to avalanche danger.

Expect 3-5″ of snow today above 1000′ today.  Snow will start to diminish in intensity over the next few hours. The brunt of this storm will taper by end of day Friday.

Friday 5 am. Goodbye snowstake!

 

Beginning of Valentines Storm 2/14

Fri, February 18th, 2022
Upper Elevation
Above 3,500'
4 - High
Avalanche risk
Mid Elevation
2,500'-3,500'
4 - High
Avalanche risk
Low Elevation
Below 2,500'
4 - High
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.
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

2 to 4 ft thick persistent slabs will be very likely to human trigger on all aspects, at all elevations today on slopes steeper than 30°. Natural avalanches are likely. It will be possible to remotely trigger large avalanches from adjacent or below slopes.

The problem weak layers are the December 26 crust/sugar facet combo and the November basal, sugary facets. In many cases this season, avalanches have failed on top of the crust, and then stepped down deeper into the weak basal facets. We expect to see both these layers fail in this not so sweet Valentines storm. Shallower southerly aspects will see more avalanche activity.

Our anemometers are still frozen from freezing drizzle during the beginning of the storm. It is snowing so hard this morning that the snowstake is nearly buried!

4 of the 5 red flags have been present over the last 24-48 hours. New snow, Recent avalanches, Collapsing/Cracking, and Rise in temperature. Last night we saw nearly 2″/hour of snow for 10 hours!

Very dangerous avalanche conditions. Travel in avalanche terrain is not recommended.

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
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

Storm Slabs up to 24″ thick will be very likely to human trigger on all aspects at all elevations on slopes steeper than 35°. Natural avalanches will be likely.

Approximately 18-20″ of new snow and an additional 3″ of water over the past 24 hrs have rapidly accumulated at 3550′. Frostbite station at 2700′ is reporting 14″ of new snow and 2″ of water.

It will be very likely for storm slabs to step down into the persistent slab, increasing the size and consequence of an avalanche.

 

Weather
Fri, February 18th, 2022

NWS AVG Forecast here.

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

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