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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Wendy Wagner  
Saturday, February 21st 2015
Created: Feb 21st 5:17 am
Summary and Current Conditions

The Summit Lake area continues to have a very thin snowpack and be snow starved as the rest of Alaska, and the Western half of the U.S. for that matter. Despite this, there is enough snow above treeline to avalanche and last week we saw several natural avalanches associated with a warm and windy storm. Another storm has just moved in last night and will impact the region through the weekend with rain up to 1,500'-2,000'. See Primary Concern below for more details on this weekend's storm and expected avalanche concerns.

On Monday, February 16th, a powerful storm blew through the Southcentral region with widespread avalanche activity. The Summit Lake area only received 0.4" of water at the SNOTEL station but winds were strong out of the Northeast, averaging near 40mph with gusts in the 60's. Total snowfall during the storm at the upper elevations was around 5-10". Alex McLain put together some photos and a write up of much of the aftermath when skies cleared. Below is a photo from Alex showing one of the larger natural avalanches on Moose Mountain (Mile 52).

 
Since Monday's storm there were three clear sky days where we were able to assess the snowpack. Read Heather Thamm's observation here and watch the video! What was found was a very unstable snowpack. The set up is essentially: one foot of dense slab (old and new snow) over a 2-6" of weak faceted snow over a stout melt-freeze crust. This is a combo similar to Turnagain Pass but the slab is much thinner - only a foot compared to 2-3'.

Photo below from Thursday Feb 19th on Manitoba - Slab avalanche ingredients: Slab / Weak Layer / Bed Surface


Snow surface conditions at Summit Lake on Thursday before the Storm moved in late Friday.
 


Primary Concern

With a very poor snowpack structure to start with (explained above, and if you didn't watch the video check it out HERE) and another round of snow and strong wind on tap, avalanche conditions over the weekend will be increasing. How much snow and wind the Summit Lake area receives will determine how much natural activity will be seen. Although there is uncertainty for natural activity, human triggered avalanches will remain likely whether or not this storm produces. That said, very careful route finding to avoid slopes over 35 degrees is recommended.

With a known layer of faceted snow buried around 1' deep it will take very accurate snowpack evaluation if you are considering getting on slopes over 35 degrees - this is a very hard thing to be confident in when there are facets involved. As the saying goes, "facets can't be trusted". The other thing about facets is they can persist in the snowpack and for days and even weeks. Along with that, this weak layer is relatively shallow and finding trigger points in this thinner slab will be easier than in other areas such as Turnagain.

*Safe days this week can be had in the Summit Lake zone by sticking to the lower angle terrain and not messing with buried facets!


Mountain Weather

Last week was marked by one significant weather event - the February 16th warm, wet and windy North Pacific storm. This storm only put down 0.4" of water and roughly 5-10" of snow at the upper elevations. Winds were out of the Northeast in the 30-40mph range with gusts in the 60's. The rain/snow line was around 1,500'.

Tuesday, Wednesday, Thursday and most of Friday saw mild temperatures and light Northerly winds with no precipitation.

Beginning last night (Friday night) another warm North Pacific storm is rolling through. This system looks to be a bit warmer but still windy and will persist through the weekend. We are expecting up to 0.5" of water with a rain/snow line up to 2,000'. Winds look to be in the 30mph range from the Northeast and diminish after today, Saturday.

Stay tuned to the main weather page for current weather info and as always check the Fresno Ridge weather station, Summit Lake SNOTEL and DOT RWIS stations for the most current weather information at Summit Lake.

This is a general backcountry avalanche advisory issued for Summit Lake Area as the core advisory area(this advisory does not apply to highways, railroads, or operating ski areas).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Feb 22, 2015 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThe CNF is in a sad state of affairs this winter in terms of motorized use. A drive over Turnagain pass in late-February looks like the monsoon season of September/ October. Though unprecedented, Rangers have not given up hope yet on a snowmachine season.... Remember March 2014??? 5 feet of snow in 5 days! This is Alaska afterall!
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: Closed
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.

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USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
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