Wed, December 14, 2022 Turnagain Pass Avalanche Forecast

Wed, December 14th, 2022

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

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.

Avalanche Problem 1

Wind Slabs
N E S W NW NE SE SW

Aspect/Elevation
Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

Aspect/Elevation of the Avalanche Problem

Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

Until this next round of storms moves in tonight, avalanche issues will continue to be lingering wind slabs in exposed areas and sluffs in steep terrain. In the higher elevations, the 1.5 – 2.5 feet of new snow from Sunday night has been hit by winds from the northwest, to south, to east. If getting into zones above treeline, be sure to feel for stiff snow over softer snow and watch for any cracking or collapsing. Slabs could be anywhere from a foot to several feet thick and could be on the more difficult side to trigger.

In sheltered areas away of any wind effect, the new snow is slowly settling and bonding, but still quite soft. If getting onto the steeper slopes, even short steep slopes in the trees, sluffs could be triggered if the slope is steep enough. Tree wells are also getting larger and something to keep in our minds. A good reminder to always keep an eye on our partners.

The big news is the storm system that should bring some light snow showers this afternoon, then more snow and wind late tonight into tomorrow morning. This event looks to favor the Anchorage area and Hatcher Pass regions while here in Girdwood and Turnagain Pass we are looking at 6-8″, maybe up to 12″ if we’re lucky. It will be a warmer storm and a rain/snow mix may be seen in Girdwood. Stay tuned for tomorrow’s forecast and be sure to check hpavalacnhe.org for Hatcher Pass’s Thursday morning forecast!

Weather

Wed, December 14th, 2022

Yesterday: Overcast skies with a few sucker holes midday. Light snow flurries added 1-4″ of new snow with little water weight. Winds were light from the southeast (5-10mph) along ridgetops and temperatures were in the teens to 20’s.

Today: Another system is headed in that will bring light snow during the afternoon and peak tonight. Around 1-3″ is expected this afternoon with another 3-6+” overnight. Temperatures are warming and we could see the rain/snow line rise to 500′ or so briefly tonight before cooling back off tomorrow morning. Ridgetop winds will be light and variable until they pick up tonight into the 30’s mph from the SE.

Tomorrow: Skies should start clearing and temperatures drop as precipitation ends tomorrow morning. Ridgetop winds will be shifting to the NW and expected to blow in the 10-20mph range. Mostly clear and quiet weather is expected Friday through the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	25	2	0.1	41
Summit Lake (1400′)	18	1	0.1	31
Alyeska Mid (1700′)	26	4	0.25	43
Bear Valley (132′)	N/A	2	0.1	–

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	20	SE	9	29
Seattle Ridge (2400′)	22	SE	7	13

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
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

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