Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 9th, 2021 - 7:00AM
Expires
Sun, January 10th, 2021 - 7:00AM
Forecaster
Jed Workman
The Bottom Line

Wind slabs will be generally small in size and possible to human trigger at the upper elevations on West, Northwest and North aspects today. Natural avalanches are unlikely. By this evening and into tomorrow, expect this hazard to increase along with sustained strong winds.

It will be unlikely to trigger a Persistent Slab today at all elevations and all aspects. Triggering an avalanche in isolated or extreme terrain is still possible. Low danger does not mean no danger.

Rocks and other hazards are still lurking just below the surface, with generally shallow snow coverage getting caught in even a small avalanche could have high consequences.

Riding conditions are decent in isolated areas that are protected from the winds.

 

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Sat, January 9th, 2021
Upper Elevation
Above 3,500'
Moderate (2)
Avalanche risk
Mid Elevation
2,500'-3,500'
Low (1)
Avalanche risk
Low Elevation
Below 2,500'
Low (1)
Avalanche risk
Upper Elevation
Above 3,500'
Avalanche risk
Moderate (2)
Mid Elevation
2,500'-3,500'
Avalanche risk
Low (1)
Low Elevation
Below 2,500'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Two small, natural wind slab  avalanches observed on Marmot, likely occurring Wednesday or Thursday. Strong winds lasted through 5am Friday.

1/6-7, Shoulder of South Ridge of Marmot, SW, 3100′, HS-N-D1-I x2, est. 6-8″ thick.

No other avalanches have been observed or reported this week. We hypothesize this is partially due to the reduced number of backcountry users at HP because of poor riding conditions.


Conditions photos:

East ridge of Hatch Peak, South aspect, 3700′, showing severe wind scouring to the ground and poor riding conditions.

 

Eldorado East, showing upper elevation wind scouring and shallow coverage, and cross-loading of features at mid elevation.

 

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

Winds are forecasted to increase this evening, but we are already seeing spike gusts this morning, SE 45 mph  at 4500′, and SE 25mph at 3500′ The wind forecast for this evening is E 17-38mph at 3000’+. The winds may have arrived a bit early in the forecast, so expect some new wind slab development from overnight, and continuing through today and tonight.

Wind slabs will be small in size, generally thin, 3-6″ thick, and in some isolated locations up to 8″, on leeward aspects, generally West, Northwest, North at upper elevations. Without much snow available to transport, wind slabs will remain relatively small today. These slabs will be possible to human trigger at upper elevations and natural avalanches are unlikely.  At mid and lower elevations, wind slabs are unlikely to human trigger and natural avalanches are unlikely.

Remember that any avalanche triggered, even a small one, carries the added consequence of rock hazards due to a generally thin snowpack.

Any triggered wind slabs will not be large enough to step down into buried persistent weak layers, yet. If wind speeds continue or increase today and into this evening, expect the wind slab avalanche hazard to increase overnight and into tomorrow, with thicker and larger wind slab avalanches and for the sensitivity of triggering to increase. As this problem grows, it may have the ability to overload persistent weak layers deeper in the snowpack.

 

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

This is just one of those years. Not a whole lot of snow to play with, barely cohesive enough to make a snowman, shallow, with rock hazards poking out in defiance in areas with even the thickest coverage, and a weak snowpack which will activate avalanches with any heavy load. The best we can hope for right now if for a good old 1970’s deep freeze, to vaporize what snow we have and turn it all into, you guessed it, Square Powder India Pale Ale from the Bear Paw Brewery! Keep your eyes peeled for this special edition, drink the snow blues away Ale while supporting your local avalanche center, coming soon.

Persistent slabs will be unlikely to trigger today at all elevations and aspects. Small avalanches are possible in isolated or extreme terrain. Large avalanches are very unlikely, but not impossible. Stability is improving very slowly.  See pit here from 1/5 for a visual reference of the layering of the current snowpack. Yesterday’s observation HERE.

Riding conditions remain variable at best with coverage varying from zero to 6 feet deep, often varying this much in as little distance as 50 feet.

Southerly and Easterly aspects have seen the brunt of winds this season, and are therefore scoured with thin coverage, zero to approximately 2.5 feet in places. The leeward aspects, northerly and westerly, have received wind blown snow through the season and therefore have a thicker snowpack, approximate 3-6 feet deep. Both aspects have poor structure, however the Southerly and Easterly have weaker structure in general with thinner slabs on top that are more easily triggered.

As we have been pointing out all season, because the coverage is so thin, taking a ride in any size avalanche will likely result in collision with rocks, compounding the hazard and increasing the overall danger. With so little reward due to poor riding conditions, the risk is even less enticing.

Even though the avalanche hazard is low, continue to use safe travel protocol, travel with partners, ride slopes one at a time, identify and use safe zones, and choose slopes with gentle runnouts lacking terrain traps.  Always ensure all members of your party carry beacons, shovels and probes and be practiced in companion rescue.

Weather
Sat, January 9th, 2021

New snow 1/7-1/9:

Independence Mine: 1″ of new snow


Weather this week started out cold and calm, but began to shift towards warmer temperatures with an increase in winds at ridgetops.  Temps hovered in the lower 20°’sF at 4500′, and dipped to 16°F early this morning.  The spike in winds on 1/6-8 settled down on Friday, but then picked back up, appearing earlier than expected in the forecast Friday evening and overnight. Very little new snow this week, leaving little new snow for transport. Today’s forecast is calling for a 30% chance of precipitation and if it does, a trace of new snow. Winds are forecasted to increase this evening, but we are already seeing spike gusts, SE 45 mph,  at 4500′.  The wind forecast for overnight is E 17-38mph at 3000’+.


Marmot Weather Station 1/7-9

Last 24 hour gusts

Independence Mine Snotel 1/7-9

Temperatures from 1/7-9 at 3500′ averaged 26°F, with a max of 32°F on 1/7 and a min of 20°F on 1/8.

Winds have increased this morning with a max gust of  SE 25mph at 4am.


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

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