Tue, April 09, 2013 Turnagain Pass Avalanche Forecast

Tue, April 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

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

I suppose if it’s not going to be full on spring, it might as well be full on winter. Yesterday’s snow (and possibly another inch or two today) should help refresh and fill in many of the old tracks. Some of us were hoping for a bit more in this neck of the woods but we’ll take it nonetheless.

Today, loose snow avalanches should be easy to initiate. These sluffs will likely run far and fast as they will be sliding on hard surfaces underneath – predominantly on south, west and east aspects. On steeper more sustained slopes they could entrain significant amounts of snow so plan accordingly.

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

Though winds have been light, so is the snow. It will not take much to move the new snow and deposit it into soft slabs. These should be fairly touchy if you find one and around a foot deep. They are likely confined to the upper elevations and on most aspects due to the changing wind directions. Watching for cracking in the snow around you and feeling for stiffer snow over softer snow will be good clues to suss out any wind slabs.

Additional concerns:

Sun: Keep a close eye out for when the sun makes its first appearance. Solar heating will quickly destabilize the new snow and sun induced point releases and shallow slab avalanches could be fairly widespread. This may not occur for a couple days but it looks like there is a small chance skies could break this afternoon.

Weather

Tue, April 9th, 2013

The big snow event that is hitting Anchorage and Hatcher Pass is leaving the Eastern Turnagain Arm a bit high and dry. Snowfall has tapered off this morning but, we have squeaked out several inches of very low density snow – and may pick up another inch or two today. Storm totals at the precip stations around the Arm since 6AM yesterday are:
Turnagain Pass SNOTEL (1900′): 4″ snow – .3″ water eq.
Alyeska Mid Mt (1700′): 7″ snow – .45 water eq.
Summit Lake SNOTEL (1400′): 2″ snow – .1 water eq.

The two SNOTEL sites typically under-represent snowfall when it’s this light. So, we are likely looking closer to 6-8″ on Turnagain Pass and 3-4″ in the Summit area.

Winds associated with the snowfall began light out the east and have shifted around to the NW overnight where they are averaging 5mph with gusts to 10mph. The NW flow is bringing is very cold air and temperatures are currently in the single digits on the ridgelines and the low teens at 1,000′.

Today we can expect lingering snow showers to add another inch or two. Temperatures will be in the 10-15F range above treeline and 15-20F below treeline. Winds look to be light out of the NW (5mph gusting 10mph).

The cold air and scattered snow showers look to remain in place through Thursday.

Kevin will issue the next advisory tomorrow morning, April 10th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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