Tue, April 02, 2024 Turnagain Pass Avalanche Forecast

Tue, April 2nd, 2024

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

2 - Moderate

Wed, April 3rd, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

Wed, April 3rd, 2024

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.

Recent Avalanches

Many storm snow avalanches were reported yesterday afternoon when skies cleared and temperatures warmed. These seemed to be around a foot deep, maybe more in places with more snow. One group on Eddies and one on Tincan both noted easily triggered storm snow slabs on small rollovers. They also noted much higher snowfall amounts than were forecast. At Eddies almost 2 feet of snow was seen at the parking lot, Tincan around 14-16″ of new snow.

Natural storm snow avalanches on the roadside of Seattle Ridge in a cross-loaded gully. One propagating crown can be seen along with some rollerballs and loose sluffs. Photographed from Tincan yesterday by Andy Moderow, 4.1.2024.

More examples of the many loose snow sluffs that occurred when temperatures warmed and the sun peered through. Thanks again to Andy Moderow for the photo. 4.1.2024.

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

Clearing skies, breezy west to northwest winds, and cooling temperatures are expected today after several days of stormy weather. Yesterday’s snowfall event, the last in a multi-day series of storms, overproduced significantly in some areas. If you are headed out today, it will be prudent to pay attention to how much new snow is under your feet or machine. Avalanche conditions will be directly related to how much new snow fell. The more snow the higher the danger. Listed below is a best guess at snowfall totals as well as the various types of new snow avalanche concerns that exist out there. This is a day to be extra cautious and look for those red flags (recent avalanches, cracking and collapsing/whumpfing in the snowpack, and afternoon warming). The trick is an avalanche may occur without any warning signs prior. To avoid these problems we can always stick to the lower angle slopes with nothing steeper above us.

Snowfall totals – mid elevations – estimated:
Girdwood: 6-10″ (on top of 2-3 feet over the weekend)
Portage/Placer: 8-12″ (on top of 1.5-2 feet over the weekend)
Turnagain Pass: 10-24″ (much more on the north end of the Pass, only 6″ over the weekend)
Summit Lake: 2-3″ (over 5-7″ over the weekend)
Seward/Lost Lake: 6-8″ (over 1.5-2 feet over the weekend)

Storm Slabs: The new snow from over the weekend as well as yesterday sits over varying degrees of crusts and hard snow surfaces. How well the snow is bonding is a question and something to be on the lookout for. Storm slabs could release on these old surfaces or in mid-storm layers, making them range from as shallow as 6″ to as deep as 3 feet deep.

Wind Slabs: Keep an eye out for older wind slabs from the storm as well as fresh wind slabs forming from today’s northwesterly winds. Watching for areas with wind deposited snow and cracking in the snow around you are great ways to suss out wind slabs. Because of the uncertainty of the new snow bonding with the older snow, wind slabs may propagate wider than expected.

Dry Snow Sluffs: Sluffing in the new snow should be expected today. Sluffs could be large and unmanageable in bigger steep terrain. They could also trigger a slab avalanche composed of the new snow.

Wet snow sluffs: If the sun is able to overtake the cool temperatures on southerly aspects watch for wet loose avalanches. These could be triggered naturally or by a person. Similar to dry sluffs, they could trigger a slab below and create a much larger avalanche.

Cornices: Remember to give these features a wide berth as they can break further back than expected. They also have the ability to trigger avalanches below and create a dangerous situation.

Deep snow at Eddies on the north end of Turnagain Pass. Around 2 new feet of snow was observed. The group said skinning conditions were a bit challenging at times! 4.1.2024.

Weather

Tue, April 2nd, 2024

Yesterday: Periods of heavy snowfall were seen yesterday with some sunshine peering through in the afternoon. The rain/snow line hovered around sea level to 200′. Between 10-20+ inches snow fell in Turnagain Pass, 6-10″ in Girdwood Valley, 5-7″ at Seward and what looks to be a couple inches at Summit Lake. Ridgetop winds were gusty from the east averaging 15-20mph with gusts in the 30s. Temperatures were in the mid 30s at sea level and mid 20s along ridgelines.

Today: Skies should be clearing through today with valley fog possible. No precipitation is expected. Ridgetop winds shifted northwesterly early this morning and are expected to blow around 10mph with gusts in the 20s. These winds are bringing in cooler air with temperatures in the mid 20s F at sea level and teens along the higher peaks.

Tomorrow: For Thursday clouds are looking to filter back in with light winds from the south. There is a chance for a few snowflakes as well adding up to maybe an inch in some areas. The temperatures will be on he rise with the southerly winds; back to the mid 30s F at sea level and mid 20s F along ridgelines.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	28	6	0.6	100
Summit Lake (1400′)	29	2	0.2	48
Alyeska Mid (1700′)	29	7	0.6	115
Bear Valley – Portage (132′)	34	3	0.6	–
Grouse Ck (700′)	34	6	0.8	81

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	18	NE	12	38
Seattle Ridge (2400′)	23	E	7	16

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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