Wed, November 29, 2017 Turnagain Pass Avalanche Forecast

Wed, November 29th, 2017

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

3 - Considerable

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

New snow, rain and sustained winds overnight have elevated the avalanche danger. 8-10″ of snow fell at upper elevations in Girdwood and 5-8″ at Turnagain in the last 24 hrs. Winds were easterly 20-30 mph with gusts into the 50s. Unfortunately some of the precipitation has fallen as… yuck, rain to around 1500′, maybe a bit higher. It is 34F at the Center Ridge Snotel (1880′) this morning. Yesterday the balance had not quite been tipped by new snow and wind loading but there was widespread cracking, whumpfing and a recent small natural avalanche observed (red flags). Hand pits showed failure on isolation between new snow and the underlying facets. This weak snow rests either on the ground or overlying a melt-freeze crust near the ground. With the additional snow and wind loading overnight this now sits below a more cohesive slab. Triggering a slab on steep terrain will be likely, especially in leeward, wind loaded areas. This snowpack set-up has the potential to be very touchy. Collapses (whumpfs) may propagate failure over large pieces of terrain and remote triggering an avalanche is possible. Don’t let early season stoke lure you into a dangerous spot. Overall it is still fairly shallow and rocky, getting caught in an avalanche could take you for a very unpleasant ride. Rain falling on this snowpack will also add weight and break up bonds. Wet loose avalanches may run naturally at low elevations in steep channeled terrain.

Quick snowpit at 1000′ near large collapse. Weak facets below new snow.

Cracking in snowpack near skin track, propagating across terrain.

Weather

Wed, November 29th, 2017

Yesterday was mostly overcast with light precipitation on and off throughout the day. Turnagain saw a few breaks in the clouds. Winds were easterly 10-20 during the day, ramping up overnight into the 30s with gusts into the 50s. Overnight snow picked up and rain fell to around 1500′. 8-10″ of snow fell at upper elevations in Girdwood with .6-1″ of SWE (snow water equivalent). Turnagain picked up 5-8″ at .5 SWE. Temperatures were in the mid 30Fs to mid 20Fs depending on elevation.

Today will be mostly cloudy with snow showers. These showers may be locally heavier at times due to unstable air behind the current front. An additional 1-5″ of snow is forecasted to fall. Winds will be easterly 10-20 mph with gusts into the 30s. Rain/snowline is expected to drop as temperatures cool down in the afternoon/evening. Temperatures will be in the mid 30Fs to mid 20Fs. Light snow showers may continue overnight.

Thursday will be mostly to partly cloudy and cooler with a wind shift to the NW. Temperatures will be in the 20Fs dipping into the teens at night. There is a break in the stormy pattern on Friday before more unsettled weather moves in again over the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	6	.5	12
Summit Lake (1400′)	32	0	0	7
Alyeska Mid (1700′)	32	8	.6	14

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	ENE	28	56
Seattle Ridge (2400′)	26	rimed	rimed	rimed

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
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
04/10/24	Turnagain	Avalanche: Cornbiscuit	Tyler Grundstrom
04/07/24	Turnagain	Observation: Seattle Creek Headwall	Troy Tempel

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