Fri, February 03, 2017 Turnagain Pass Avalanche Forecast

Fri, February 3rd, 2017

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

1 - Low

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

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

It’s that time of year! The sun is out and affecting the snow in terrain on the Southern half of the compass. With 4-8″ of loose snow on the surface over a dense base, watch your sluffs and watch how the sun is affecting the snow around you.

Wind Slabs? There is a slight chance winds could bump up enough to form soft shallow slabs on leeward slopes. Although the main flow will be Northwesterly, loading Southeasterly aspects, this pattern also creates a Southerly flow along the East side of Turnagain Pass which loads North aspects (such as Sunburst and Tincan).

Avalanche Problem 2

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

With February already here along with a high pressure stint bringing sunshine, it may be easy to forget many areas in Southcentral have a poor snowpack structure. As mentioned in the bottom line above, weak snow near the base of the pack exists on slopes with a thinner snow cover. The heart of Turnagain Pass has drawn the lucky ticket and the pack is deeper and stronger with avalanche concerns focused on surface instabilities (sluffs and shallow fresh wind slabs).

If deciding to venture to the periphery zones, watch for recent avalanche activity, listen for whumphing (collapsing of the snowpack) and cracks that shoot out from your snowmaching, skis or snowboard. There also can be no warning signs before an avalanche is triggered. This type of avalanche is often triggered in a thin spot, near rocks or on the edge of the slab. These can also be triggered by large groups and/or snowmachines on, near or under slopes. Again it will be critical to maintain safe travel protocol, again as mentioned above.

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

Cornice falls are possible with warm temperatures and sunshine. These could release naturally and be near the tipping point that person breaks them off easily. Keep a wide berth when on ridgelines and limit time underneath.

Photo: Cornice fall yesterday in Warmup Bowl in the Seattle Creek drainage. Triggered from a person on the ridge later in the day.

Weather

Fri, February 3rd, 2017

It was a brilliant sunny day in the mountains yesterday with little to no wind at all elevations! Temperatures were cool (~10-15F) in valley bottoms and warmer (20-30F) on the ridgelines.

Today will be much of the same with two slight changes, but first, bring your dark lenses as the sun will be intense. 1) Ridgetop winds have just bumped up slightly this morning and could be breezy for the day (5-15mph from the North and West, gusting 10-20mph). Temperatures have climbed overnight at the high elevations and sit around 32F – valley bottoms have decreased and sit in the single digits… Another blocking high-pressure and associated stout inversion is settling in…

These conditions are expected to persist all the way through the weekend and into Monday. There’s no hint of a storm cycle in the foreseeable future, but we could get some flurries the middle part of next week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	19	0	0	55
Summit Lake (1400′)	10	0	0	24
Alyeska Mid (1700′)	21	0	0	49

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	W	3	16
Seattle Ridge (2400′)	24	NE	3	10

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.