|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.|
One avalanche was reported yesterday. It was in the Girdwood Valley (Notch Mtn) and was a skier triggered shallow 6″ thick soft slab that propagated on a rollover (photo below).
Shallow soft slab, skier triggered, in the Notch Mtn area of Girdwood Valley. Although too small to catch and bury a person, additional snowfall today may create a larger slab, big enough to cause grief. 1.15.21. Photo: Peter Symmes.
|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|
And the weather keeps coming. After 4-6″ of new snow fell yesterday morning, clouds parted and let the sun in for a several hours midday. This was a brief reprieve before clouds moved in last night ahead of today’s weather system. As of 6am this morning, another 3-6″ of new snow has fallen and ridgetop winds are blowing consistently in the 30-45mph range with stronger gusts. Today’s event should bring 6-10″ of snowfall by this evening and another few inches overnight tonight. Avalanches today should be associated with the new snow and winds. They’ll be in the form of wind slabs, storm slabs (where there is over 6″ of new snow), sluffs and cornice falls. At elevations below 1,000′ where it’s raining, wet sluffs are a concern.
The strong winds will not only be blowing the new snow into sensitive slabs, but the existing loose surface snow as well. Wind slabs are likely to be in the 1-3′ thick range and even thicker just off ridgelines where it’s been blowing since midnight. Being that it’s storming today, areas with active wind loading should be easy to see and avoid. Be sure to stay out from under steep slopes that are getting loaded above you; for example under the steep face of Seattle Ridge pictured above. Watching for cracking in the snow around you and stiffer snow over softer snow is also a clue you’ve found a wind slab.
In areas out of the wind that see over 6″ of new snow, watch for storm slabs. These will be soft slabs as seen in the photo from Notch Mtn yesterday. They can propagate across the whole slope and even if they are only 6-10″ thick, can generate a good amount of debris in bigger terrain.
Cornices: With poor visibility, it’s unlikely a person will find themselves along a ridgeline, but one good way for a natural avalanche to occur is when a chunk of cornice breaks off. Cornices are growing with each storm and we’ve seen many of them start falling. Another good reason to avoid being under or on slopes with cornices above.
New 2020/21 CNFAIC forecaster Andrew Schauer takes a look at the snowpack on Sunburst yesterday. 1.15.21. Photo: Paul Wunnicke.
Yesterday: Light snow showers in the morning were followed by clearing afternoon skies before clouds and snowfall pushed back early Saturday morning. Up to 5″ of low density snow was seen in Girdwood with a few inches on Turnagain Pass fell with the morning pulse and so far only a few inches has falling early this Saturday morning. Ridgetop winds were light and variable yesterday before ramping up overnight with the next system. Temperatures were near 30F at the mid elevations and the low 20’sF along the higher ridgetops.
Today: Moderate snowfall and strong winds are expected today as a quick hitting storm has moved in from PWS early this morning. Between 5-10″ of snow is forecast (~.7″ SWE) with a rain/snow line right around 1,000′. Ridgetop winds are averaging 35-45mph with gusts near 60mph from the east, where they are expected to remain through the day. Temperatures are rising and should peak midday in the mid-30’sF at 1,000′ and mid 20’sF along the high peaks.
Tomorrow: A brief break in storms is expected for Sunday before a more potent system arrives Sunday night through Monday. This event could bring an additional 2 feet of snow from 1000′ and above with strong easterly winds (expected rain/snow line between 500-1000′). A High Wind Watch has been issued by the National Weather Service for this storm.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||29||3||0.3||124|
|Summit Lake (1400′)||25||1||0.1||41|
|Alyeska Mid (1700′)||29||6||0.6||115|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||SE||15*||33|
*Estimated hourly wind average. Sunburst and Seattle Ridge anemometers have rime on them and were not reporting yesterday.
|11/27/23||Turnagain||Avalanche: Tincan Ridge||Schauer/ Stiassny Forecaster|
|11/26/23||Turnagain||Observation: Road report: Slide with dirt on Repeat offender||Anonymous|
|11/26/23||Turnagain||Observation: Pete’s North||Ben Sullender|
|11/25/23||Turnagain||Observation: Tincan trees||John Sykes Forecaster|
|11/21/23||Observation: Spokane Creek||John Sykes Forecaster|
|11/19/23||Turnagain||Observation: Magnum – PMS Bowl||Schauer/ Cullen/ Jonas Forecaster|
|11/19/23||Other Regions||Observation: Sunnyside/Penguin||Jose Ramos-Leon|
|11/19/23||Turnagain||Observation: Eddies||Andy Moderow|