Thu, April 16, 2015 Turnagain Pass Avalanche Forecast

Thu, April 16th, 2015

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

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

Tuesday provided a heavy dose of localized (to Turnagain pass) storm snow in the core advisory area with up to 19” accumulating at the Center Ridge SNOTEL site (1880’) in 19 hours. The storm quickly shut off with only a trace of snow falling yesterday allowing Tuesday’s storm slab to settle to about 12”. This load coupled with 3-5” forecasted today is enough of a concern to warrant careful snowpack and terrain evaluation before skinning up or jumping into committing terrain.

Storm slabs/ wind slabs:

These are expected to be as deep as 1-2’ in areas affected by the wind, proving large enough to bury a person. We don’t have a lot of information in terms of how well this recent storm is bonding to, or affecting underlying weaknesses so it’ll be prudent to pay attention to any red flags including recent avalanches, shooting cracks or whumphing prior to committing to steep terrain. If experiencing and red flags today, these are the sure signs that the snowpack below your skis is unstable and slope angles need to be dialed back. Quick hand pits or jumping on small (no consequence) test slopes will be a good way to gather more data while making your own snowpack assessment.

Deep slab/ persistent weak layers:

This is less of a concern today but is still being pondered, particularly on the South end of the advisory area where persistent weak layers may be found closer to the surface.

With the majority of the ski season behind us, now is not the time for complacency. Continue to practice safe travel protocols. Ski slopes one at a time and utilize lookouts, positive communication, escape routes and islands of safety.

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

Natural and human triggered sluffs are expected in the new snow on all aspects and elevations. Though the Sun isn’t forecasted to make an appearance today, warm ambient temperatures and potentially rain at lower elevations may be enough to trigger loose snow sluffing and roller balls above and below treeline.

Weather

Thu, April 16th, 2015

Yesterday’s weather can be described as Grey-bird and warm with light winds from the east. Temperatures reached 40 degrees at 1880′ with ridgetop winds gusting into the low 20’s mph. Temperatures dipped to the low 30’s overnight, winds stayed calm and just a trace of snow has fallen over the darkest hours of the night.

Today a low pressure system is making its way from the Gulf of Alaska toward the Susitna valley bringing us a chance for 3-5 € of snow at 1,000′ as it moves through. Winds will be light from the SE in the 12-20mph range with temperatures in the mid 30’s today dropping to the mid to high 20’s as this low pressure clears the Kenai Peninsula. The potential exists for lingering snow showers to sea level by later this evening.

By Friday afternoon another low pressure and associated front will be moving into the Gulf spreading rain to coastal areas and snow showers to the higher elevations.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	1	.2	81
Summit Lake (1400′)	36	0	.02	12
Alyeska Mid (1700′)	34	1	.2	39

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	E	8	29
Seattle Ridge (2400′)	27	n/a	11	22

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

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