Sat, March 05, 2016 Turnagain Pass Avalanche Forecast

Sat, March 5th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

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

A weak storm system has entered the Eastern Turnagain Arm region this morning. Snowfall has just begun and Easterly winds have just picked up. We are expecting 3-5″ of snow today above 1,000′ with rain below (this rain/snow line could creep up through the day and we could see more than 5″ of snow in places). With this new snow and ridgetop winds in the 15-30mph range, we can expect shallow wind slabs to be forming. These slabs will be sitting on this past week’s variable surfaces (sun crust, wind crust, soft settled powder). How well the fresh slabs will bond with the old surfaces will be the question today.

If you are headed out pay close attention to:
1) How much snow has fallen.
2) What are the winds doing. Are they transporting snow along the ridgelines? Are they loading slopes?
3) How well is the new snow/wind loaded snow bonding with the underlying surface? Quick hand pits can be good to suss this out.

Cornice falls: As is the general rule, these are worth avoiding/limiting time under as they continue to break off. Today they will get stressed a bit more with new snow and wind.

Photo below: Pete’s North ridgeline from yesterday. Recent cornice falls can be seen along the ridge.

Avalanche Problem 2

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

Although we have a short burst of snowfall and wind on tap today, glide avalanches remain just as much of a concern. This is due to the countless number of glide cracks in places folks recreate and the destructive nature of a glide avalanche in the event one does release. There were several glide cracks that slide yesterday in the Summit Lake area and one possible new glide avalanche in the Lynx creek drainage. All that said, it’s worth keeping a lookout for cracks and minimizing time under them – no question!

Photo from yesterday: Very large glide crack on the SW face of Cornbiscuit. You can see tracks on the looker’s left of the 8-12+’ deep crack.

Weather

Sat, March 5th, 2016

Partly sunny skies, with some blue holes, covered the region yesterday. A morning snow squall added a trace of snow at sea level in Girdwood (and a few inches in Anchorage – causing some driving mayhem) but this all missed Turnagain Pass. However, snowfall has started to fall this morning and as of 6am we have seen 2″ accumulate. Winds during the past 24-hours have been steady averaging ~10mph with gusts to 20mph. Temperatures have been in the mid 20’s F on the ridgelines and ~30F at 1,000′.

Today we have a weak system moving over us from the East. This will give us a chance for 3-5″ of snow with a rain/snow line between 1,000 and 1,500′. Temperatures should climb through the day and peak around 35F at 1,000′ and the upper 20’sF on the ridgelines. Winds are slated to bump up to the moderate-to-strong category from the East along the ridgetops (15-30mph with stronger gusts).

This system looks to exit this evening and tomorrow, Sunday, we should see party sunny skies with a possible snow shower here and there. Stay tuned.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	25	2	0.2	139
Summit Lake (1400′)	25	0	0	42
Alyeska Mid (1700′)	25	2	0.15	104

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	NE	8	23
Seattle Ridge (2400′)	26	–	–	–

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/27/23	Turnagain	Avalanche: Tincan Ridge	Schauer/ Stiassny Forecaster
11/26/23	Turnagain	Observation: Road report: Slide with dirt on Repeat offender	Anonymous
11/26/23	Turnagain	Observation: Pete’s North	Ben Sullender
11/25/23	Turnagain	Observation: Tincan trees	John Sykes Forecaster
11/21/23		Observation: Spokane Creek	John Sykes Forecaster
11/20/23	Turnagain	Observation: Sunburst	Anonymous
11/19/23	Turnagain	Observation: Magnum – PMS Bowl	Schauer/ Cullen/ Jonas Forecaster
11/19/23	Other Regions	Observation: Sunnyside/Penguin	Jose Ramos-Leon
11/19/23	Turnagain	Observation: Eddies	Andy Moderow
11/19/23	Turnagain	Observation: Cornbiscuit	Anonymous

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