Sun, April 05, 2015 Turnagain Pass Avalanche Forecast

Sun, April 5th, 2015

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

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

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

Although a storm is slowly rolling in today for the early part of the week, we are still concerned about weak snow sitting under a 2-3′ slab on Northerly aspects. For the past 5 days we have been investigating a number of buried weak layers that were highly reactive Tuesday through Friday and over the weekend have shown signs of gaining strength. Despite the decreasing possibility of triggering a slab, good travel habits are important to stick to if venturing into the soft snow on Northerly slopes. This means exposing one person at a time, watching your partners, having escape routes planned if the snow moves and have all your rescue gear in working order and know how to use it.

Avalanche Problem 2

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

Fresh shallow wind slabs and loose snow avalanches may be found today with an expected 2-6″ of new snow. Ridgetop winds are forecast to be just strong enough to move the new snow around and build soft slabs anywhere from 4-8″ thick. These are not likely to pack much of a punch unless more snow and/or wind develops. In some areas they will be forming on a slick crust and if you find a larger 8″ pocket, say, it could run further than expected.

Sluffs in the new snow should be expected on steep slopes (where enough snow accumulates). If steep South slopes warm later in the day, natural wet/damp sluffs will be likely, yet low volume.

Additional Concern

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

Cornices will continue to deserve respect from now until they are melted out or calved off. It’s also important to remember that daytime heating can weaken their roots and increase the likelihood for collapse, natural or human triggered.

Check out the photo from Friday below, yikes. Sadly, Alaska had its third avalanche fatality last week when a cornice broke taking a skier with it. This happened in the Wrangell-St Elias area and while details are currently being gathered, you can see the preliminary write up along with the Nation’s other fatalities HERE.

“Things not appearing as they seem” and “Don’t follow our tracks!” were the quotes referring to the photo. This was sent in to us from two longtime supporters of the CNFAIC that were skiing the North ridge of Eddies Bowl. See their write up HERE.

Weather

Sun, April 5th, 2015

Yesterday’s impending sunny and warm day was cut short with clouds and a cool breeze moving in by the afternoon. High temperatures were around 30F on the ridgetops and 45F at 1,000′. Ridgetop winds were from the East in the 5-15mph range.

Overnight, precipitation has started up in some areas associated with a large low-pressure system in the Bering. This is pushing a warm front in from the Southwest and up Cook inlet (a good set-up for precipitation in Anchorage). Although Turnagain Pass is still dry this morning, the Alyeska Mid station (1,700′) has picked up 3″ of new snow! We should see an additional 2-4″ of snow through the day. Winds will be light to moderate from the South and East, 10-15mph. Temperatures in the mid-20’s F on the ridgelines and low 30’s F at 1,000′. We should see snow to, or very close to, sea level.

Monday and Tuesday the bulk of the precipitation and stormy weather is expected to hit us. Temperatures look to warm enough for rain as high as 1,000′, possibly higher, and precipitation amounts are in the .5-1″ of water range by Tuesday evening. Stay tuned.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	0	0	58
Summit Lake (1400′)	33	0	0	10
Alyeska Mid (1700′)	35	3	0.25	33

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	E	9	26
Seattle Ridge (2400′)	27	n/a	10	35

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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