Sat, February 09, 2013 Turnagain Pass Avalanche Forecast

Sat, February 9th, 2013

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

3 - Considerable

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

Wind Slabs

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.

More info at Avalanche.org

Wind Slab

The winds have begun cranking up into the 60 mph range this morning at ridgetops. Light density snow that fell two days ago combined with new snow will get blown around to form sensitive wind slabs today. Yesterday multiple parties reported seeing good bonding between the newest storm snow/wind slab and the old snow surfaces. The reactivity of the surface snow will increase today and will be most easily triggered as new slabs are forming. With potentially very rapid loading occurring today (50+ mph winds and up to 12″ of new snow forecasted), these slabs will be very sensitive to human triggers.

A general lack of persistent weak layers in the upper snowpack will focus my attention on the interface between yesterday’s snow surface and today’s new snow. The exception to this are very isolated pockets of surface hoar that were observed on Tuesday. With high winds expect loading to occur further downslope than normal as well as in the lower elevations.

Storm Snow

Below treeline an additional 6-8″ of new snow on its way will build slabs on a slick and hard crust that will be easy to trigger. While these storm snow slabs will be smaller than new wind slabs they are worth looking out for today. Watch for these slabs to be most easily triggered on steep rollovers in the lower elevations.

Be on the lookout for the most obvious signs of unstable snow: avalanches, shooting cracks and “whoompfing”/collapsing. If and when you are seeing these signs this is nature screaming in your ear, “Hey, it’s time to back off and turn around!”

Avalanche Problem 2

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

The deep slab problem has not shown itself in the form of an avalanche in almost a month. While this lack of activity is an encouraging sign, there is still weak snow at the base of the snowpack, primarily above 2,000′ in elevation. While the chance is remote for a deep slab avalanche to occur today, it is still worth remembering what is deep down in the snowpack. Relatively smaller avalanches initiated in the upper snowpack have the potential to step down in older layers of snow near the ground. This problem has a greater potential to show itself in areas of more shallow snow as evidenced here.

Weather

Sat, February 9th, 2013

A generally calm day in the mountains yesterday has given way to increasingly high winds this morning as a large and well organized low pressure center moves towards the region. Snow has begun to fall and ridgetop temps are currently in 20s F.

The NWS has issued the following warning:

…HIGH WIND WARNING REMAINS IN EFFECT UNTIL 4 PM AKST THIS
AFTERNOON FOR PORTAGE VALLEY AND TURNAGAIN ARM…

* LOCATION…PORTAGE VALLEY AND TURNAGAIN ARM.

* WIND…SOUTHEAST 45 TO 65 MPH WITH GUSTS TO 85 MPH.

* TIMING…STRONG WINDS WILL CONTINUE THROUGH EARLY THIS
AFTERNOON. WINDS WILL BEGIN TO DIMINISH LATE THIS AFTERNOON.

Wind will be the major player in creating dangerous avalanche conditions in the mountains today. New snow will play a close second in this equation. Snow fall amounts should be in the 6-12″ range and temps at 1,000′ will be in the low 30s F

Winds should back off slightly by this evening and snowfall should continue overnight and into Sunday.

______________________________________________________________

Wendy will issue the next advisory tomorrow morning February 10th.

______________________________________________________________

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

Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.