Thu, January 29, 2015 Turnagain Pass Avalanche Forecast

Thu, January 29th, 2015

Alpine

Above 2,500'

1 - Low

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

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

We’ve received great info from a Level 3 avalanche class that has been conducting fieldwork in both Turnagain pass and Summit Lake area over the last several days. Students yesterday found a generally strong snowpack with shallow, stubborn wind slabs on Seattle ridge (Sunny side) that would not propagate under a skier’s weight. Across the road where moderate westerly winds have not been so destructive the surface consisted of 2-4” of near surface facets capped by growing surface hoar yesterday. Below the surface data and a lack of avalanche activity continues to validate the high strength, low propagation potential in the Turnagain pass area.

In terms of moving through the mountains today, any pockets of instabilities observed should be relegated to the upper 3-6” of the snowpack and will likely be in the form of older, shallow wind slabs on leeward slopes. Look for these pockets of denser snow and be mindful of your terrain choices, weighing the consequences of popping off a shallow wind slab. This will be particularly important in steep, (greater than 40 degrees) upper elevations where you may be exposed to terrain traps below. If we receive more than 4” of snow today and winds kick up enough to actively transport snow, expect shallow wind slabs (5-10”) to be more reactive to human triggers.

With a few inches of snow in the forecast, any new wind slabs could also prove problematic to ice climbers exposed to funneled terrain in areas such as Portage Valley.

Avalanche Problem 2

Normal Caution

Normal Caution

Normal Caution means triggering an avalanche is unlikely but not impossible.

More info at Avalanche.org

Glide avalanches are still littered throughout the forecast area and with a bit of a warm-up today we’ll be keeping an eye on any glide crack movement or release. Your best bet remains to limit your time spent underneath glide cracks, as they remain an unpredictable beast.

Glide cracks and glide avalanches (already released) litter the South and West aspects of Eddies.

photo: Jaime Andersen

Low snow coverage:

Below 2000’ low snow coverage is deceiving with only a few inches of new snow covering rocks, ice and vegetation. Take your time getting in and out of the alpine today.

Weather

Thu, January 29th, 2015

Valley fog persisted throughout the day yesterday with mostly sunny skies above about 500′. Temperatures warmed slightly throughout the day to the low-20’s at ridgetop locations. Winds were light and variable, generally in the single digits through the daylight hours.

Today temperatures are expected to continue to climb to the mid-20’s at ridgetops with easterly winds in the 4-14mph range. A weak band of increased clouds and precipitation is trying to push into our region today and it’s likely we’ll see 1-3 € of snow in the eastern Turnagain arm region by nightfall.

By Friday afternoon skies are expected to clear with high pressure, sunshine and dry offshore flow dominating our weather through the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	23	0	0	31
Summit Lake (1400′)	15	0	0	6
Alyeska Mid (1700′)	18	0	0	22

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	NE	7	17
Seattle Ridge (2400′)	20	variable	4	13

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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