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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Heather Thamm  
Saturday, January 21st 2017
Created: Jan 21st 5:44 am
Summary and Current Conditions

Summit Lake on the Kenai continues to have a VERY thin snowpack. Friday, January 20th into Saturday morning, January 21st, roughly 10” of snow has fallen and possibly another 3-10” may fall throughout the day today (Saturday.) Elevated avalanche danger exists today (Saturday) and dangerous avalanche conditions could persist through the week in the Summit Lake Zone.  A big shift in our current weather pattern is expected to bring more snowfall (possibly rain) and warming temperatures to Southcentral, AK early next week. Stay tuned on the most current up to date avalanche and weather conditions on the Turnagain Pass daily advisory. Also, Please help us keep tabs on the Summit area - if you see any avalanche activity send us an observation HERE. Thank you to everyone who has already submitted observations this season - you can see those HERE!

Summary and Current Conditions: The snowpack below this weekend’s storm in the Summit Lake zone is best described as shallow, weak and variable. A generally dry and cold winter has faceted out the snowpack creating a poor foundation on all aspects. In the alpine several strong wind events have loaded many slopes in the upper elevations with hard wind slabs sitting on rotten/faceted snow. The most recent wind event on Wed (1/18) loaded East and South aspects causing several natural wind slabs to release to the ground. In the lower elevations, protected from the winds, the whole snowpack is loose and faceted and today’s snow load has elevated the avalanche hazard on all aspects. In the upper elevations expect hard slabs to release near the ground and in the lower elevations new storm slabs and older deeper slabs could also be unstable. Basically this week’s avalanche concerns will be directly proportional to how much new snow Summit Lake area recieves and how warm temperatures will rise. Any active weather (snow/rain or winds) will keep the avalanche danger elevated. Should the weather mellow out and stabilize this week careful snowpack evaluation, caution route-finding,  and conservative decision making are essential.  

Natural wind slab that relased to the ground on an East aspect of Fresno Ridge sometime between Wed (1/18) and Thurs morning (1/19) as a result of strong Northwest ridgetop winds. This is also a good example of how shallow the snowpack is in Summit Lake. 

 


Primary Concern

Snow depth numbers and details - before Friday night's new snow:

Parking lots - to 2,000':  15“-20” old faceted snow and depth hoar (crusts have degraded into facets and depth hoar). The avalanche danger in the lower elevations will be directly proportaional to how much snow fall on this poor foundation.

Above 2,000' and in the Alpine:  Variable! 0-5 feet of total snow depth due to wind distribution. Several crust/facet layers sit near the ground with mid-pack buried surface hoar lurking in some places. Hard wind slabs sit on these weak layers and it's good to remember poor structure exists despite the stubborn nature of triggering a slab in deeper areas of the snowpack. Likely trigger spots will be near ridge lines where the snowpack is thin.

Photos below from CNFAIC staff this week - check out Heather’s video and snowpack observation from Fresno Ridge on Thursday, HERE, and Alex's recent snowfall observations from Seward and Summit Lake on Saturday morning (1/21) at 4am  HERE. 

There is much uncertainty going into the weekend/comming week about how the snowpack will adjust following today’s storm and a possiblity of more precip in the coming days. It will depend on how much of a load the snowpack recieves. More snow = more danger. There is also much uncertainty about how the extended forecast will directly impact the Summit Lake area. Don't forget persistent weak layers like facets take a long time to heal before they go away, thus this problem is likely to linger for awhile and will be elevated this weekend and with any additional loading. Expect all aspects to harbor this set-up with Northern and Eastern aspects the most suspect due their shallower depths and most recent activity this last week. Since the most recent snow (1/20-1/21) has arrived without much wind visual wind loading clues (scoured ridges/loaded gully’s) may be difficult to see over the weekend. Facets have been found on all aspect and elevations over the last month and all slopes steeper than 30 degrees are suspect. Remotely triggering a dangerous slab avalanche is possible this week, thus maintaining safe distances from run-out zones will be important. Recent avalanche activity, collapsing sounds "wumpfing", and shooting are all obvious signs that the snowpack is unstable and all avalanche terrain should be avoided. 

Weak faceted grains and depth hoar are sitting on the ground in the lower elevations. This photo was taken on Thurs (1/19) on a SE aspect of Fresno at 2000'. Expect to find this unstable snow on all aspects in the lower elevations.

 

 


Secondary Concern

Click HERE to see the most current Summit Lake observations. Below are photos from last week of what Summit Snowpack and snow coverage looked like before today's (1/21) most recent storm. 

A snow pit at 2700' on a SE aspect of Fresno Ridge shows the poor structure in the upper elevations where the snowpack consists of a hard slab sitting on rotton (faceting) snow near the ground. On Western aspects where the snowpack is a little deeper it may be tougher to trigger this problem, but this structure has been found over the last few weeks on all aspects.  

 

Recent avalanche activity on E facing gully's on Colorado Peak. Notice how scoured Nothern ridges are in comparison to the Southern ridges in the photo below.

 

Southeast ridges are more loaded than usual like the SE ridge of Fresno just below the weather station. These kinds of thinly covered ridgelines are more connected to loaded slopes and my be suspect for remotely triggering avalanches on adjacents slopes.  

 

Notice how much more snow coverage is on the Western and Southwestern aspects. These areas are still suspect of basal and mid-pack weakeness (facets and buried surface hoar.)  

 

Southeast aspect of Summit. Photo taken on 1/19 by Alex McLain

 

Southeast of Gilpatrick. Photo taken on 1/19 by Alex McLain. For more photos of this area on January 19th, click HERE.

 

 

 


Mountain Weather

Last weekend a storm left 6-8” of snow throughout Summit Lake area. Throughout the week skies were mostly clear and temperatures were below normal for the region ranging from 15F last weekend to 0F-10F throughout the week. Last Wednesday (1/18) into Thursday morning (1/19) ridgetop winds were strong (20-40mph) from the Northwest.

Overnight 10” of new snow fell in Summit Lake and another 3-4” is expected. However some uncertainty exists within today’s forecast and should this frontal system linger longer than expected an additional 10” is possible in the upper elevations of Summit Lake. Snowfall should taper off by early evening. Temperatures are around 15F and winds are expected to remain light (10-15mph) from the South. 

Tomorrow winds are expected to remain light, but temperatures could drop back into the single digits (F) in Summit Lake.  Light flurries are possible. Early next week a big shift in the jet stream, South to North orientation, is expected to bring rising temperatures (above freezing) along the coast and another shot of precipitation is on tap for Southcentral, Alaska.

The best way to see if it's snowing at Summit Lake is to look at the RWIS webcam snow stake HERE and the NRCS snotel site HERE. The above MP 45 station is the best ridgetop wind and temperature information. Fresno Weather Station will not be opportational for the rest of the season. 

 

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: Jan 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenAccess is thru the gate on the right side of the parking lot as you drive toward the outhouse. Please park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlease cross Railroad tracks at 90 degrees to the rails and clear the corridor. It is Illegal to ride up and down Railroad tracks. Tracks are currently active. Please observe and stay off PRIVATE PROPERTY adjacent to the Portage Valley.
Skookum Drainage: Open
Turnagain Pass: Open
Twentymile: OpenPark at Portage rail depot. Cross tracks and follow marked corridor (Bamboo poles) approx. 3 miles up Valley to open riding areas.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenOpen to motorized use 1/15. Please STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenOpen to motorized use 1/15. Please 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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