Tue, March 17, 2015 Turnagain Pass Avalanche Forecast

Tue, March 17th, 2015

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

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

After waiting for months and months we finally got a true shot of winter yesterday on Turnagain Pass! A fast moving storm moved in late Sunday and by the time it moved out yesterday evening (24-hours later) we had over 2′ of new snow. The new snow came in with very strong Easterly winds and those have died down as well. As far as new snow amounts? Below is a rundown on storm totals.

Weather Station Storm Totals: 2,500′ Estimated Storm Totals:

Turnagain Pass (1880′) 22″ snow / 2.0″ water Turnagain Pass 26-30+”
Alyeska Mid (1700′) 16″ snow / 1.3 water Girdwood Valley 18-22+”
Summit Lake (1400′) 13″ snow / 0.9 water Summit Lake 14-16+”

Although visibility was hampered yesterday, we were able to see a few debris piles at the bottom of gullies pointing to natural avalanche activity occurring above. Several human triggered slides occurred as well in the Tincan Trees, photos below.

Today, the storm is past and natural avalanches are not likely, but human triggered avalanches are and this is the most dangerous time for skiers and riders. If the skies clear enough for travel above treeline, managing terrain will be essential. This means sticking to slopes 35 degrees or less and staying out from under slopes or steep gullies and terrain traps in the trees.

Photos below are of two skier triggered slab avalanches in the Tincan Trees yesterday. Report from yesterday is HERE.

Certain slopes harbor faceted snow under the 2′ of new snow and this set-up (photo below) will allow for remotely triggered slides and the potential for triggering an avalanche from below. Although not all slopes have this layering, we are still too close to the tail end of the storm to jump into steeper terrain in general.

Weather

Tue, March 17th, 2015

Yesterday was the first bona fide storm snow day of the season, believe it or not!! The storm began Sunday night and peaked mid-day yesterday with snowfall rates exceeding 2″/hour and a storm total of 22″ at the Turnagain Pass SNOTEL. 24-hour totals are below in the charts. Easterly ridgetop winds peaked mid-day as well with averages as high as 65mph and gusts in the 80’s. Temperatures hovered in the mid to upper 20’s on the ridgetops and near 32F at 1.000′ (just enough for damp/wet snow in the parking lots).

The storm moved out yesterday evening and overnight skies have cleared and winds have died down. Today, this short break will be replaced by another system headed our way late tonight. Skies should remain mostly cloudy with a few flurries through the day while winds will continue from the East in the 15mph range. Temperatures will be on a slow rise, up to 30F at treeline and the upper 20’s on the ridgetops.

The pattern responsible for our return to winter is a large complex low South of the Aleutians, which has a series of embedded disturbances tracking Northward through the Sound and into Southcentral. This pattern will continue through the week and bring additional snowfall. The rain/snow line should be around 1,000′ and possibly higher tomorrow.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	30	17	1.6	61
Summit Lake (1400′)	31	13	0.9	22
Alyeska Mid (1700′)	31	10	0.9	40

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	ENE	27	89
Seattle Ridge (2400′)	25	Wind	Sensor is	Rimed…

Storm Day at the Pass!!

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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