Sun, March 31, 2013 Turnagain Pass Avalanche Forecast

Sun, March 31st, 2013

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

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

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

Wind slabs formed during Friday, 3/29’s 8-10” of snow were still releasing yesterday. These were in the foot deep category and on all aspects above treeline. A few observed were: one natural that occurred on the east face of Seattle Ridge and one on the southerly tip of Tincan Proper. Check the obs page for a few more details from other observers. The sun and warm temperatures likely played a role in increasing the instability of the slabs.

Today I’m expecting these to be harder to trigger but still the primary concern due to their slab nature. The snowpack is quite variable currently with wind slabs sitting on crusts on south, east and westerly aspects (some of which have facets surrounding them) and on old wind crust/slabs on northerly aspects. Quick hand pits looking for easy shears between snow layers in the top 12-18” of the pack is one good tool to suss out any slab that has yet to heal.

Avalanche Problem 2

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

Wet point release and damp point release avalanches should be expected today on south, east and westerly facing slopes approaching 40 degrees and steeper. Watch for rollerballing in the surface snow and be suspect of areas and aspects where the snow surface is warm and gloppy.

Additional Concerns:
Cornices. Warm temperature are known for contributing to the failure of cornices. A good thing to keep in mind when planning your route.

Surface Conditions:
Yesterday’s warmup affected the south, west and easterly aspects as well as below treeline locations. These areas that became damp or wet yesterday are likely undergoing a superficial refreeze now but should moisten through the day. Upper northerly aspects sport variable wind affected, but dry, snow.

Weather

Sun, March 31st, 2013

It was a WARM day yesterday with temperatures reaching the 40deg mark at sea level and 30F at 3,000′. Skies were partly cloudy with a few flurries (drizzle below 1500′) late in the day. Winds were light from the east (5mph gusting 15mph). The last measurable snowfall was 8-10 € on Friday 3/29.

This morning we are looking at mostly cloudy skies, fog and temperatures around freezing (32F) at 1,000′ and ~20F on the ridgelines. Temperatures should rise to the upper 30’s at 1000′ and upper 20’s at 3,500′. A chance for an inch of snow is on the radar (drizzle below 1000′) as instability showers are over the region. Winds are from the east currently, 10mph gusting ~15mph, and should remain today. I’m hoping the cloud cover will burn off a bit for the CORN HARVEST so cross your fingers.

Monday, and through the early part of this week, it looks as though a high pressure ridge will build over western Alaska. This should bring us light northerly wind and mostly clear skies.

Fitz will issue the next advisory tomorrow morning, April 1st.

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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