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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Wendy Wagner  
Saturday, March 11th 2017
Created: Mar 10th 20:54 pm
Summary and Current Conditions

The Summit Lake area on the Kenai has sat under blue skies and cold temperatures since the last days of February. A significant wind event rolled through between Feb 27th and March 3rd. Widespread large natural avalanches, that released near the ground, were triggered by the winds loading leeward slopes. Since March 3rd there have been no known avalanches in the Summit Lake zone or surrounding areas. The last snowfall in the Summit area was 4-8" of low density snow from Feb 21st.

The entire winter at Summit Lake has been characterized by a shallow snowpack with various weak layers including basal facets and depth hoar near the ground. The snow depth is anywhere from 2-6' deep in general, has been highly wind affected and the snow redistributed. 

Looking to the weekend: Direct sunshine has a bit of heat to it these days. If air temperatures increase and winds remain light this weekend, expect the loose surface snow to being getting damp. In this case, roller balls or shallow wet loose avalanches (sluffs) could occur. Additionally, warming of the snowpack can loosen old wind slabs, cornices and even slabs that are sitting on old weak faceted snow near the ground - making them possibly easier to trigger. (More on this below)

*During the week, stay tuned on the most current up to date avalanche and weather conditions on the Turnagain Pass daily advisory and the Summit Lake Observations Page! Also, Please help us keep tabs on the Summit area - if you see any avalanche activity send us an observation HERE

 

Photo below from Alex McLain: Not a cloud in the sky at Summit Lake on Friday, March 10th. 

      

The South face of Tenderfoot Ridge on March 2nd. You can see an old avalanche crown lower on the slope and up the drainage. Thin coverage has been the theme this season with roughly just over half the snowpack we are used to.

 

Another great Heather Thamm photo of Manitoba's South face on March 2nd. Again some old crowns visible from the wind event in early March.



Photos below are of an avalanche control training mission by the AK DOT on Wednesday March 8th. The AK DOT Avalanche Program used their "Daisy Bell", a unit that hangs off the bottom of a helicopter and creates an air blast over targeted areas of an avalanche starting zone. The Summit Lake side paths were used in the training and no avalanches were triggered. 

                                     


Primary Concern

There are a variety of avalanche concerns to keep in mind if venturing to the Summit Lake area. These are:

Persistent Slab Avalanches:
Underneath the old wind affected snow on the top portion of the snowpack, the bottom consists of weak faceted snow and depth hoar. This weak basal snow is why the wind event was able to overload and create avalanches that broke near the ground (the last known slide being March 3rd). Facets have been found in the mid-pack as well. These layers have adjusted and are not showing to be reactive, however outliers can always occur when facets are involved. That said, although unlikely, triggering a slab that breaks in the old faceted snow could be large and dangerous. 

Wind Slabs:
Old hard wind slabs, prevolent on many slopes, are likely to be very stubborn and hard to trigger. Most likely places to trigger a wind slab is in steep rocky terrain where they are not supported from below.

Cornices:
Cornices are large and if significant warming occurs this week, they could begin to loosen and be easier to break off.

Sluffs:
Dry loose sluffs on steep slopes that harbor loose surface snow should be expected. If the sun comes out this week, wet loose avalanches could being to occur naturally or be triggered by a person.

NEW SNOW?
There is a chance for new snow later in the coming work week. Keep tabs on the Turnagain Pass daily advisory. However, expect any new snow to have a hard time bonding with the existing old surface.


Mountain Weather

Cold and clear weather has dominated during the past week. Ridgetop winds that racked the region have backed off significantly since March 3rd and have been blowing from the Noth in a light to moderate range. Temperatures have been hovering anywhere between the minus single digits and the teens Fahrenheit. On Friday, March 10th, a warming trend began and temperatures climbed into the 20sF at all elevations during the day before dropping off to near 5F overnight in the valley bottoms.

For the weekend, we can expect similar clear sky conditions. However, daytime warming should increase temperatures into the 20's-30 F at most locations. In the mornings, expect cold air to pool in valley bottoms from overnight. Ridgetop winds are expected to be light to moderate from the North and East. There is a hit for snow later this week so stay tuned on Turnagain Pass Advisory!

For the most current weather information visit the CNFAIC weather page HERE.

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: Mar 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
Skookum Drainage: OpenSKOOKUM DRAINAGE CLOSES TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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