Sun, January 01, 2023 Turnagain Pass Avalanche Forecast

Sun, January 1st, 2023

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

Below Treeline

Below 1,000'

4 - High

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
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

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.

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

2023 is crashing in with heavy rain, snow, and wind – Happy New Year!

A strong storm system is over the Eastern Turnagain Arm and already there has been around 1″ of rain at sea level and 10-14″ of snow in the higher elevations. The storm will peak today and taper off tomorrow. Today’s precip could bring 1-2″ of additional rain and up to 2 feet of snow to favored areas above 2,000′ (check out the graphic below). Turnagain Pass itself has seen 14″ of snow as of 6am with up to 18 more inches forecast today. The rain/snow line was around 500′ last night but expected to rise to 1,500′ by this afternoon and into tomorrow. Ridgetop winds are easterly and strong; hourly averages have been 30-40mph with gusts in the 70’s and should remain strong through the day.

Natural Avalanche Cycle: Avalanches are likely occurring now in the mid and upper elevations due to the strong wind and heavy snowfall. It’s a textbook case of strong storms = avalanches. With 2-3 feet of new snow and wind in the Alpine, avalanches composed of just the new snow could be 2-4′ deep. These are the typical storm slab and wind slab avalanche types. As the rain/snow line rises and temperatures warm, this only adds to the instability by heavier snow/rain falling on lighter snow. Wet or moist snow storm slab avalanches could start releasing in the mid elevations with this ‘upside down‘ setup. Rain on snow at the lower elevations may or may not be creating wet snow avalanches as the prior snowpack was mainly crusts from the rain that occurred during the Christmas Storm. However, debris from avalanches above could run to the bottom of paths into the lower terrain.

If you are planning on braving the roads and getting outside today, be aware that travel in avalanche terrain is NOT recommended. This is the kind of day for sleeping in, and letting the mountains do their thing.

As of 6am 10-14″ of snow has already fallen above 1,500′. Another 12 to even 24″ of snow could fall today above 2,000′. Graphic courtesy of NWS Anchorage.

Avalanche Problem 2

Persistent 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

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Aspect/Elevation of the Avalanche Problem

Likelihood of Avalanches

Size of Avalanches

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

This storm is the second large loading event for the snowpack. It will again test those buried weak layers that sit around the Thanksgiving crust, or even any weak layer that may be left from the Christmas Storm a week ago. Again, we will do our best at seeing if any storm snow avalanches are able to break into buried weak layers. This will be an indicator of how those layers are healing and if they will continue to be a problem in our future or not. For now however, this deeper problem is just one more reason why avoiding avalanche terrain is a good call.

Weather

Sun, January 1st, 2023

Yesterday: The New Year’s storm began yesterday with light rain at sea level and snow above ~500′. An estimated 8-14″ of snow has fallen so far above 1,000′, most of which occurred overnight. Ridgetop winds picked up into the 30-40mph range with gusts in the 70’s from an easterly direction. Temperatures are in the mid 30’s F at sea level and in the mid 20’s in the Alpine.

Today: The brunt of the storm will be today bringing an additional 10-16″ of snow at elevations above 2,000′. The rain snow line looks to rise as high as 1,500′ by midday (plus or minus). Ridgetop winds are easterly blowing 30-40mph with gusts that could reach 80-100mph. Temperatures will slowly rise through the day to near 40F at sea level and 30F near ridgelines.

Tomorrow: Lighter precipitation is forecast for Monday as the storm tapers. Around 3-5″ of snow should trickle in with the rain/snow line remaining fairly high (around 1,500′). Ridgetop winds look to still be strong (20-30mph averages) from the E to SE. Weather models are showing active weather through the week with another stronger pulse Tuesday into Wednesday.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	14 (est.)	1.4	52 (est.)
Summit Lake (1400′)	31	3	0.3	29
Alyeska Mid (1700′)	31	6	0.5	40
Bear Valley – Portage (132′)	36	rain	1.6	–

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	NE	36	72
Seattle Ridge (2400′)	26	SE	12*	25*

*Seattle Ridge anemometer became rimed over around midnight last night, no data since 11pm Dec 31.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
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

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