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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, March 25th, 2022 - 7:00AM
Expires
Sat, March 26th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche Warning
Issued: March 24, 2022 6:00 am
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line

The avalanche danger is HIGH for a second day in a row and an AVALANCHE WARNING remains in effect. This is due to heavy snowfall and strong winds in the mountains surrounding Turnagain Pass, Girdwood Valley, Portage Valley, and other areas on the Kenai. Dangerous avalanche conditions exist on all slopes 30 degrees and steeper – including runout zones. Large avalanches are likely to release naturally and human triggered avalanches are very likely.  Travel in avalanche terrain is NOT recommended. Areas with steep slopes above should be avoided, such as the Byron Glacier Trail and the Seattle Ridge up-track. Even small terrain features could act as deadly traps.

SUMMIT LAKE:  A very weak snowpack exists in the Summit Lake area. New snow with strong wind could produce very large avalanches that break on buried weak layers.

SEWARD/LOST LAKE/SNUG HARBOR:  This storm is creating HIGH avalanche danger across the region including near Seward and Snug Harbor.

Special Announcements
  • AKDOT&PF:  There will be intermittent traffic delays Friday March 25, 2022 on the Seward Highway, from mileposts 88 to 85 (south of Girdwood), and near mile post 5 and Bear Valley on the Portage Glacier Highway, for Avalanche Hazard Reduction work. Motorists should expect delays of up to 45 minutes between 09:00 AM and 2:00 PM. Updates will be posted at 511.alaska.gov.
  • EAGLE RIVER:  A large natural avalanche occurred last night that has put debris on the Hiland Road. There are few details currently, but they can be found HERE.
Fri, March 25th, 2022
Alpine
Above 2,500'
4 - High
Avalanche risk
Treeline
1,000'-2,500'
4 - High
Avalanche risk
Below Treeline
Below 1,000'
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
  • 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

Travel in avalanche terrain is NOT recommended – it’s that simple right now.

March is going out like a Lion and bringing with it very dangerous avalanche conditions. The powerful storm over the region is peaking as we speak and looks to continue into Saturday. As of 6am this morning (Friday), the mountains have seen between 2-4 feet (yes, feet!) of new snow with strong easterly winds. Another 6-12″ is expected through the day today above 1,000′ with rain below 1,000′.

The new snow has fallen on various weak layers (buried surface hoar, near surface facets, and sun crusts). These were the old surfaces from last weekend. All of these layers will keep the new snow from sticking and despite the poor visibility, we can expect that large natural avalanches are occurring now. These can be any of the various storm snow avalanches such as storm slabs and wind slabs up to several feet deep and cornice falls. Avalanches could be even larger than just the storm snow if the older buried weak layers become overloaded, which will add significantly to the volume. All in all, we have a dangerous setup and do not be surprised if debris from natural avalanches reaches further into valley bottoms than we have seen this season so far.

Tincan trees and other areas with short steep rolls – for those looking to stay away from the bigger terrain, smaller terrain could be a big problem too. Be aware that storm slabs are now up to 3′ deep and even a small roll that avalanches could push and bury someone in a depression or against a tree.

Valley bottoms and runout zones:  Being extra cautious and truly avoiding all avalanche terrain and staying well away from run-out zones is critical. This includes the popular motorized Turnagain Flats under Seattle Ridge where there are many areas that can seem safe, but are not. If you are unclear about what areas are safe and what are not, it is best to avoid the mountains all together.

Storm total snowfall estimates at 2,500′ beginning Wednesday to 6am Friday:
Girdwood Valley:   24-36″ snow, 2.9″ water equivalent
Turnagain Pass:   24-40″ snow,  3.3″ water equivalent
Summit lake:    5″ snow, 0.4″ water equivalent

 

We saw 16″ of new storm snow at 1,200′ on Turnagain Pass in the trees just above the road yesterday around noon. Up to 2 additional feet has fallen since then, with another possible foot today. 3.24.22. 

 

Graphic courtesy of the NWS Anchorage Office that show the forecast storm total from yesterday afternoon through Saturday. We are already partially into this forecast period. 

Avalanche Problem 2
  • 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

After seeing how touchy the snowpack was for John and Allen on their field day at Pete’s North on Wednesday, it is likely that the new storm snow is overloading at least one buried weak layer. Before this storm there were two layers of buried surface hoar, one from March 2nd that wasn’t very reactive, and one from March 16th, which was quite reactive and caused over 10 human triggered avalanches last weekend. It was this March 16th layer that John was easily able to trigger on Pete’s North. It was around 1-2′ deep in the snowpack before the storm, so right now it’s close to 3-5′ deep. It also was creating avalanches that propagated very wide. With that said, we could have avalanches that are up to 5 feet deep and propagate across terrain features. Again, a very dangerous setup.

Weather
Fri, March 25th, 2022

Yesterday:  Moderate to heavy snowfall was seen across the region with a rain/snow line around 800′. Snowfall totals for the past 24-hours were in the 1-2′ range with highest amounts reported at Alyeska, Portage Valley and Turnagain Pass. Ridgetop winds have remains strong from the east, 30-40mph averages with gusts in the 70’s. Temperatures are on a slow rise and hovering near 32F at the mid elevations and the low 20’s along ridgelines.

Today:  The storm will continue through today with heavy snowfall this morning that should slowly taper by this evening. Between 6 – 12″ of additional snow is expected by sunset with a rain/snow line near 1,000′. Ridgetop winds will also continue to be strong from the east, 25-35mph with gusts near 60. Temperatures should remain fairly warm (upper 30’sF sea level, 32 around 2,000′, 20’sF along ridgelines).

Tomorrow:  Models are showing cloudy skies with some light snowfall persisting into Saturday into Sunday as the storm slowly moves out. Ridgetop winds also look to back off into the 10-15mph range from the east. Temperatures will be on a slow decline back to the 20’sF at most locations.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 22 2.3 128
Summit Lake (1400′) 31 5 0.4 45
Alyeska Mid (1700′) 32 10 1.5 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 NE 38 76
Seattle Ridge (2400′) 26 N/A* N/A* N/A*

*The Seattle Ridge anemometer is rimed over due to the storm and not reporting wind data.

Observations
Recent Observations for Turnagain Pass
Date Region Location Observer
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05/12/24 Turnagain Observation: Warm up Bowl Tony Naciuk
05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs A S
04/29/24 Turnagain Avalanche: Turnagain aerial obs Tully Hamer
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.
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