Mon, January 24, 2022 Turnagain Pass Avalanche Forecast

Mon, January 24th, 2022

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

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
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

An intense period of snowfall and high winds is currently impacting the forecast area, with the biggest pulse of snow accumulation taking place in the early morning hours today. This storm is following a similar pattern to what we have seen over the past several days of warm and wet weather, with significantly higher amounts of precipitation in coastal areas and favoring the Girdwood valley over Turnagain Pass. Snow totals from Sunday afternoon through Monday evening should be over 24″ in Portage and Placer, 12 to 24″ for Girdwood, and closer to 8 to 16″ for Turnagain pass. Snow line is forecast to be between 500 to 1000′ today, rising throughout the day. In addition to the snowfall, winds have been averaging over 50 mph since 1 am on Sunburst with gusts up to 90 mph. Continued strong winds throughout the day today will be transporting snow at mid and upper elevations.

Travel in avalanche terrain is not recommended. Large avalanches releasing in the upper elevations could run into lower elevations, so be aware of overhead hazards if you are travelling in avalanche paths in the treeline or below treeline elevation band today.

Wind slabs 1-4+’ deep will be very likely for a person to trigger and likely for natural release in areas that are seeing active wind loading from the strong SE winds. In protected areas the new load of storm snow could also cause avalanches up to 2′ deep, depending on how well the new snow bonds with the existing snow surface. Since the peak precipitation amounts are happening just before daylight the storm snow will likely be touchy during the first half of the day as it needs some time to bond with the underlying surface. The heavy new load of snow could also reactivate buried weak layers, such as the facets over the New Years crust, which could cause very large avalanches on specific terrain features.

Cornices: The new snow and strong winds will be rapidly building cornices today which could release spontaneously or be reactive to human triggering.

NWS snow water equivalent forecast through Monday evening, with 1 to 1.5″ for Turnagain, 1.5 to 2″ for Girdwood, and 2+” for more coastal areas. Graphic courtesy of NWS Anchorage 1.22.22

Weather

Mon, January 24th, 2022

Yesterday: Warm and wet weather with active snow and rain starting around noon in Turnagain Pass and increasing in intensity throughout the day. Moderate winds during the daylight hours which bumped up to strong winds with very strong gusts after midnight, especially at upper elevations. Temperatures stayed above freezing at lower elevations with snow rain line around 1000′.

Today: Heavy snow and rain accompanied by strong winds during the early morning hours tapering off towards noon. Snow totals including Sunday afternoon and evening are forecast to be in the 1-2+ foot range, with Turnagain Pass on the lower end and more coastal areas like Portage and Placer on the higher end. Snow line should be around 500′ early Monday morning rising to 1000′ in the afternoon. Winds remain strong out of the SE during the morning with averages in the 25-50 range at and gusts possible up to 100 mph. During the afternoon winds will lighten up slightly and shift to the south.

Tomorrow: After a period of lighter precipitation during the day Monday another pulse of snow and rain is coming overnight with potential for additional 3-9″ of snowfall. Temperatures should drop early Tuesday morning and be below freezing down to sea level. Winds are forecast to be out of the south for this next pulse of moisture in the 10-30 mph range. During the day Tuesday skies look to start clearing and winds become light and variable before the next low pressure system enters the area Wednesday around midnight.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	6	0.6	83
Summit Lake (1400′)	32	3	0.2	32
Alyeska Mid (1700′)	32	12	1.1	80

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	ENE	30	90
Seattle Ridge (2400′)	26	SE	17	41

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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