Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, March 20th, 2019 - 7:00AM
Expires
Thu, March 21st, 2019 - 7:00AM
Forecaster
Aleph Johnston-Bloom
High Avalanche Danger
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line

The avalanche danger will rise to HIGH today and large to very large natural avalanches will become likely. Very warm temperatures, heavy precipitation with a rising rain/snow line and strong winds will impact the region. Travel in avalanche terrain is not recommended. Avalanches have the potential to be very deep and dangerous.  

PORTAGE VALLEY:    Travel in runout zones from avalanches including venturing along and past the Byron Glacier Trail continues to be not recommended. Very large avalanches have been observed in Portage over the past few days and are expected to continue with this next round of active weather.

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):    Extra caution is advised. Large human triggered avalanches remain likely. Avalanches have the potential to release in old buried weak layers.

SEWARD/LOST LAKE:    New snow, rain and wind will increase avalanche danger again in this region as well. Large and dangerous natural avalanches  have been observed in this area during the recent avalanche cycle.

 

Special Announcements
  • Turnagain Pass 20 years later:  On  Saturday, March 23rd from 12-2pm  swing by the Turnagain Pass moto lot and meet the CNFAIC avalanche forecasters, bring and test your avalanche rescue gear and learn about the history of Turnagain Pass and the CNFAIC. We’ll even have a few beacons buried so you can test your skills before heading into the hills!
  • Feeling sporty? Want to support avalanche education in Alaska? Head to the Alaska Avalanche School Ski-Mo (uphill/downhill) fundraiser race at Arctic Valley on  Sunday, March 24th at 1pm. For more information click  HERE. Great fun! Great cause!
Wed, March 20th, 2019
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

Wow! Getting to see the extent of the St. Patty’s Day avalanche cycle was impressive and scary. With a window of good visibility yesterday large, deep avalanches that occurred 3.17 and 3.18 were observed across the advisory area. Additionally and notably two large avalanches were observed running naturally yesterday. The Five Sisters avalanche path in Portage ran in the morning with a 10+ foot crown and a slide in Main Bowl on the back side of Seattle Ridge was observed running in the afternoon. Today the next storm system is forecast to impact the area. Temperatures are already above freezing in the Alpine, rain is expected to fall to 2500′ and winds are already gusting into the 70s on Sunburst. There is a buffet of avalanche issues today and the potential for large to very avalanches makes travel in avalanche terrain including runouts not recommended. The crust that formed with cool temperatures Monday night could eventually break down and there is either colder snow that could be over loaded as it becomes saturated or at lower elevations already very saturated snow that could move. Above the rain/snow line new snow and wind will add stress to the snowpack and cornices are large and dangerous. Investigating the very large avalanche on Tincan yesterday showed that avalanches are breaking back to the March 8th new/old snow interface made up of small facets and buried surface hoar. Multiple feet of snow now rest on top of this layer and avalanches today and tomorrow may still break down at this weakness. The snowpack will need time to adjust to all the loading from the March barrage of storms. Give it some time and enjoy other activities away from the mountains!

 

Natural avalanche in Main Bowl on the backside of Seattle Ridge observed running yesterday afternoon, 3-19-19. Photo: Travis Smith

Five Sisters avalanche path in Portage Valley was observed running yesterday morning, 3-19-19.  

 

The 3.18.19 Tincan avalanche. Photo from Seattle Ridge: Travis Smith. 

Weather
Wed, March 20th, 2019

Yesterday: Partly sunny with temperatures in the 20Fs to 40Fs depending on elevation. Winds were light and easterly. Clouds moved in overnight and temperatures were in the 30Fs and 40Fs. Easterly winds increased blowing 30-40 mph with gusts into the 70s.

Today:  Rain and snow throughout the day with close to an inch of water in the forecast. Rain/snowline is expected to be around 2500′. Temperatures will be in the high 30Fs to high 40Fs, with Alpine temperatures already in the mid 30Fs. Winds will be easterly 30-40 mph with gusts into the 60s and 70s. Rain and snow continue overnight with unseasonably warm temperatures and strong winds.

Tomorrow: The warm wet weather continues into Thursday. Expect more of the same. This active pattern extends into the weekend with a brief break on Saturday and another storm Sunday.

*Seattle wind sensor was cleared and started reporting 4 pm yesterday, data is incomplete.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36 0 0.1 86
Summit Lake (1400′)  35 0 0 29
Alyeska Mid (1700′)  35 0 0.08 76

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24  NE  18  78
Seattle Ridge (2400′) 30   SE*    4*     24*
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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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