Sat, December 02, 2017 Turnagain Pass Avalanche Forecast

Sat, December 2nd, 2017

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

2 - Moderate

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


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

Persistent Slabs

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

More info at Avalanche.org

The Kenai Mountains continue to have a very touchy early season snowpack. Over the last three days numerous human triggered avalanches have occurred in popular terrain at Tincan and Sunburst. Yesterday three avalanches were triggered remotely at the same time by one skier as they descended the ridge above Common Bowl on Tincan. See photo below. There was also a remote triggered avalanche on Sunburst near the skin track. Luckily we haven’t received word of anyone getting caught or buried. Lets keep it that way! A slab averaging 15” thick is sitting precariously on a weak layer of facets that has proven to be very reactive. Today an additional 2-6″ of snow and moderate Easterly winds 20-30mph could increase slab thickness to 2+ feet on leeward aspects. There is a lot of uncertainty as to how much wind and precip will tip the balance for natural avalanches. Either way human triggered avalanches will be likely. Lots of small terrain features in popular areas that don’t normally avalanche have been releasing. This is extremely important to understand because even a small avalanche could have high consequences especially if someone were caught in a terrain trap. Whumpfing, shooting cracks, and recent avalanches are all present and are obvious signs the snowpack is unstable. If you are headed into the mountains, careful snowpack evaluation and conservative terrain choices are required. This early season snowpack is not a good place to push your luck.

A photo taken above Tincan yesterday of Common Bowl. The three avalanches in this photo were triggered remotely by a skier descending the ridge where you can see two peope in this photo. A big THANK YOU to all who submitted observations yesterday. Check them out HERE.

This photo was taken of the furthest right avalanche from the skin track. Photo by Victoria Lytle

Avalanche Problem 2

Wind Slabs

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

More info at Avalanche.org

Today Easterly winds 20-30mph will be forming fresh wind slabs on leeward features. In the alpine where the new snow/old snow interface is more variable, wind slabs are expected to be forming in places with the poor structure described above.These wind slabs could be touchy and may break into a deeper layer of the snowpack. Either way, today is not the day to be venturing into steep terrain. Bottom line is to avoid all slopes steeper than 35 degrees.

Additional Concern

Wind Slabs

More info at Avalanche.org

Today Easterly winds 20-30mph will be forming fresh wind slabs on leeward features in the alpine. In the alpine where the new snow/old snow interface is more variable, wind slabs may be forming in places with the poor structure described above.These wind slabs could be touchy and may break into a deeper layer of the snowpack. Either way today is not the day to be venturing into steep terrain. Bottomline avoid being on or under slopes steeper than 35 degrees.

Weather

Sat, December 2nd, 2017

Skies were clear on Friday and temperatures averaged in the 20F’s. Winds were light from the West and no precipitation was recorded. Yesterday evening West winds switched to an Easterly direction as the leading edge of a front entered our region and bumped winds to Moderate (15-25mph). Light snow flurries started falling around 2am and an inch of snow was recorded.

As a front moves from the Southwest up Cook Inlet today stormy conditions will favor the Susitna Valley, but Turnagain Pass and Girdwood may see 2-6 € of snow today. Easterly winds are expected to be 20-30mph with gusts in the 40’s mph and temperature will also rise throughout the day. Snow is expected to transition to rain near sea level late tonight into Sunday morning. Rain/snow line may reach 2500′ by tonight.

Tomorrow expect heavy precipitation in the upper elevations with rain at sea level as a front moves into the Gulf of Alaska. Strong Easterly winds are expected along along Turnagain Arm and rain/snow line is expected to be around 1500′ tomorrow. Precipitation and elevated winds are expected through Monday and above freezing temperatures will likely linger into mid week.

*Center Ridge SNOTEL has a disfunctional temperature sensor and temperatures are not reliable. See Turnagain Pass DOT weather station for current temperates at 1000′.

**Seattle Ridge weather station anenometer is covered with rime is not operating at this time.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	*26	1	.1	15
Summit Lake (1400′)	16	3	.2	10
Alyeska Mid (1700′)	25	1	.11	16

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	20	W	7	33
Seattle Ridge (2400′)	26	**n/a	**n/a	**n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster

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