Tue, January 19, 2021 Turnagain Pass Avalanche Forecast

Tue, January 19th, 2021

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

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.

Recent Avalanches

Seward Highway: There was debris from natural avalanches at the bottom of avalanche paths from Bird Flats to Portage and all the way down to Mile 21 near Moose Pass yesterday. Poor visibility yesterday made it impossible to tell what kind of natural activity had occurred near Girdwood or at Turnagain pass, but with skies clearing today we will surely see more recent natural avalanches.

Avalanche Problem 1

Storm Slabs
Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

Likelihood of Avalanches

Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches

Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word	Size (D scale)	Simple Descriptor
Small	1	Unlikely to bury a person
Large	2	Can bury a person
Very Large	3	Can destroy a house
Historic	4 & 5	Can destroy part or all of a village

More info at Avalanche.org

The skies are clearing today, but make no mistake: we are still going to be faced with dangerous avalanche conditions as the snowpack adjusts to the major loading event over the MLK holiday weekend. Do not let the mild weather today lure you into a false sense of security. After receiving 1-3’ of snow in the past 24 hours, large human-triggered avalanches are likely today. Since 6 a.m. Friday, our new snow totals are as follows:

Center Ridge Snotel (1880’): 27” snow, equal to 3.9” snow water equivalent (SWE).
Alyeska Mid-Mountain (1700’): 31” snow, equal to 4.7” SWE. The base station recorded 3.4” water yesterday, which fell almost entirely as rain.
Summit Creek (1400’): 13” snow, equal to 1.4” SWE.

During days like these, people are more likely to find themselves getting into trouble with avalanche accidents and close calls. Although steeper slopes will look appealing under a fresh blanket of snow and with good visibility, conservative decision making will be imperative as the snowpack reacts to the recent heavy load. Be extra cautious with your terrain choices today, and pay attention to clear signs of instability like recent avalanches, shooting cracks, and collapsing. Until the snowpack has a little more time to adjust, we need to stick to lower angle terrain.

Cornices: Conditions have been perfect for building large cornices lately. If you find yourself traveling along ridgelines, be sure to give them plenty of space. It is also important to minimize travel below cornices, as they may release naturally and unexpectedly.

This was the scene at the motorized lot yesterday- 18″ on the ground at noon and heavy snowfall. 01.18.2021

This avalanche was triggered by a snowboarder under clear skies the day after a big storm in the end of December. The snowboarder was partially buried, but luckily was not injured. It is likely a human could trigger a similar avalanche today. 12.23.2020

Weather

Tue, January 19th, 2021

Yesterday: Intense precipitation starting early yesterday morning brought 2-3’ of snow at upper elevations, and over 2.5” of rain below 800’. The rain level snuck up to elevations around 1500’ periodically, with almost all snow above 1500’. Winds were 30-60 mph out of the east with gusts as high as 105 mph, but calmed down to 5-10 mph yesterday evening through last night. Temperatures were in the mid-20’s F at upper elevations, and in the mid-30’s F at low elevations.

Today: Mostly sunny skies and light winds are on tap today as an upper-level high pressure ridge passes over the area. Temperatures are expected in the upper 20’s to low 30’s F during the day, and will drop into the upper teens to low 20’s F tonight.

Tomorrow: There is a chance of light snow tonight, which may bring 1-3″. Cool temperatures should bring snow to sea level. Winds are expected to pick up tonight, blowing 25-30 mph out of the east at ridgetops with gusts to 35 mph. Skies are expected to be mostly cloudy during the day tomorrow, with another chance of light snowfall.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	20	2.7	144
Summit Lake (1400′)	33	12	1.3	105
Alyeska Mid (1700′)	32	25	2.9	126

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	NE	30	105
Seattle Ridge (2400′)	27	N/A*	N/A	N/A

*The Seattle Ridge anemometer is rimed over and not reporting.

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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