Sat, March 09, 2013 Turnagain Pass Avalanche Forecast

Sat, March 9th, 2013

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

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

Storm Slabs

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.

More info at Avalanche.org

The 2 day storm total has brought more than 2 feet of snow to upper elevations in the Girdwood valley (Alyeska). Turnagain Pass seems to have gotten about 75% of that amount. The storm was warmer than we’ve had recently with rain up to about 500 feet elevation. Areas below treeline will have denser snow, which dries out the higher you climb.

We have no reports of unusual avalanche activity from this storm. All reported avalanches yesterday were of predictable size and character corresponding to the storm event. Given warmer temperatures and a relatively strong and stable snowpack before the storm hit, our primary concern is the 1-2 feet of storm snow sliding at the new/old snow interface. This means we aren’t very concerned about deeper avalanches. It also means that we expect bonding to happen relatively quickly.

We are still within 24 hours of the storm event. Avalanche 101 protocol tells us that we are still in a higher probability time to trigger avalanches. Today there is plenty of moderate angle terrain to enjoy the new snow, but big gaming should be delayed another day or two to allow the new snow to settle out and stabilize.

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

Wind driven storm snow will be deepest on west and northwest aspects today with crossloading on north and south. Peak wind was 2 nights ago, corresponding with some of the highest intensity snowfall. Wind diminished yesterday but stayed strong enough to continue blowing snow around. Any avalanche found today will likely have a wind loaded component to it. Deeper and stiffer snow should be treated with more suspicion than soft and loose powder.

Cornices have been a big issue for us over the last several weeks, and given more snow and high wind we can expect larger and less stable cornices again this weekend.

Weather

Sat, March 9th, 2013

2 day storm totals

Alyeska top – 28+ inches snow – 2.54 inches of water equivalent

Alyeska mid – 24 inches snow – 1.7 inches water equivalent

Turnagain Pass – 10-12 inches snow est – 0.8 inches water equivalent

Grandview – 0.6 inches water equivalent

Weather today will bring snow showers with 1-3 inches expected. As this storm system moves through the wind will continue to drop, and temperatures should decrease by a few degrees.

There is no sun in the forecast this weekend, but clear and colder weather is expected starting Monday.

Wendy will issue the next advisory on Sunday, March 10th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
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

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