Avalanche Forecast | Hatcher Pass Avalanche CenterAvalanche Forecast | Hatcher Pass Avalanche Center 02/03/2022

Thu, February 3rd, 2022

Upper Elevation

Above 3,500'

2 - Moderate

Mid Elevation

2,500'-3,500'

2 - Moderate

Low Elevation

Below 2,500'

2 - Moderate

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


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

Several avalanches were remotely triggered by snow machines since the last forecast click here and here for more info. On 1/29 a natural avalanche cycle occurred.

1/30 Remote trigger, Lane Valley. 10 people had skied the slope before a snow machine triggered this avalanche.

1/29 Natural , Microdot S 4400

Avalanche Problem 1

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

Human triggered persistent slab avalanches 1-3’ are possible on all all aspects, at all elevations, on slopes 30º degrees or steeper. Natural avalanches are unlikely.

The structure of the snowpack is poor throughout all of the forecast area. Chances of a human triggered persistent slab avalanche are increased where the snowpack is thinner. The snowpack is thinner on SE, S and SW aspects, near ridge tops, and on the willow side of Hatcher Pass. All of the recent remote triggered avalanches occurred in rocky areas where the snowpack is thinner. These avalanches were also all triggered by snow machines. The depth of the snowpack is highly variable throughout the forecast area. On a south aspect yesterday, forecasters found a thin snowpack that was less than 1.5 feet deep. On north aspect nearby it was over 6 feet deep. It is easier to affect a weak layer where the snowpack is thinner, increasing the chances of a human or snow machine triggering an avalanche.

1/30 Southwest 4500′ This was a near miss and the snowmachiner was able to escape by riding off the slab.

To identify this avalanche problem use pole/probes and formal stability tests. Whumping and shooting cracks are red flags for this avalanche problem but may not occur prior to an avalanche being triggered

This persistent slab problem isn’t going anywhere and will likely be a concern for the rest of the season. Be disciplined when traveling in and around avalanche terrain. Practice safe travel techniques every time you head out into the mountains. Make sure you carry transceivers, probes and shovels and know how to use them. Remotely triggering an avalanche is a real concern in the forecast area.

Weather

Thu, February 3rd, 2022

The weather has been rather benign since the last avalanche forecast. With 1-2” of new snow falling since 1/29.

NWS AVG Forecast here.

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations

Recent Observations for Hatcher Pass