ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Wednesday March 20th, 2019
Posted by Aleph Johnston-Bloom on 03/20/19 at 7:00 am.
The Bottom Line
High Avalanche Danger
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

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.  

 

4. High
Alpine
/ Above 2,500'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4. High
Treeline
/ 1,000'-2,500'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4. High
Below Treeline
/ Below 1,000'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

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!
Avalanche Problem 1
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.
  • TYPE
    Storm Slabs
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

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. 

Mountain Weather

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*