Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Sunday, March 18th at 7am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).
A MODERATE avalanche danger continues for triggering a dangerous slab avalanche. These are most likely to be found at all aspects and elevations in areas just outside the heart of Turnagain Pass (e.g., Placer Valley, Twentymile and Johnson Pass) but one person was able to find one in our core zone yesterday. Wet loose avalanches are still possible on south aspects and dry sluffing will continue on northerly slopes. For safer riding areas, there is LOW danger on slopes less than 35 degrees. Remember there is a Sunday Summit Lake forecast.
We have a heads-up snowpack right now folks and though it has been four days since 2-3′ of snow fell over our area, things have changed. This latest storm has buried a variety of weak snow that is not allowing the new snow to bond to the old as quickly as it has been doing so far this year. Therefore, slab avalanche activity has continued in certain areas, despite our clear and calm weather.
1 – Turnagain Pass – Very limited details of a human triggered avalanche on Friday evening (3/16) in the Eddies/Tincan area. One person reported caught, carried and suffering injuries. We are searching for more details on this – if you have any information please send it to us.
2 – Turnagain Pass – Human triggered, 1-2′ deep, soft slab on a south facing slope yesterday (3/17). Suspect weak layer is facets on top of a buried sun crust.
3 – Girdwood Valley – Human triggered slab while ascending on skins yesterday (3/17). Believed to be on a mid-elevation northerly aspect, suspect weak layer is buried surface hoar.
4 – Fringes of the core Turnagain Pass zone – Remote triggered slab avalanche yesterday (3/17). Suspect weak layer is buried surface hoar.
5 – Outside our forecast zone – Lost lake area toward Seward – Several large heat induced natural slides yesterday (3/17).
Primary concern: Persistent Slab
Triggering a slab avalanche remains the primary concern. Buried surface hoar and facets above crusts seem to be the two big players right now causing these slabs to release. Buried surface hoar has been seen at all elevations and aspects, predominantly in Placer Valley, Twentymile and Johnson Pass while facets above crusts are being seen on southerly aspects at all elevations. The good news is the core Turnagain Pass zone seems to be least affected by these weak layers, but they are still possible to find.
Knowing if you may trigger one of these slabs is hard to determine. Paying attention to any whumphing noises or collapsing is a clue. Digging in the snow is also one great way to get an idea, but it is also not fool proof and often hard to do. What is always manageable is traveling safely (Exposing only one person at a time!) and if you don’t want to mess with it at all, keeping slope angles below 35 degrees.
Secondary concern: Loose snow
Both wet and dry point release avalanches continue to be a concern on steep slopes. Though most slopes have already had the impact of the sun for two days now, continuing to avoid areas under south facing rocky/vegetated slopes is prudent as wet point release avalanches are still possible. Dry sluffs continue to be likely to trigger on steep (over 38 degree) slopes that do not have a sun crust. These have been running both short and far, mainly on northerly aspects.
The sun broke through the clouds yesterday for a mostly sunny warm day over our region. Winds were light on the ridges, blowing between 5 and 15mph from the southeast. Temperatures climbed to over 20F above treeline and over 30F below. Overnight, winds have remained light and temperatures have dropped slightly with an inversion setting up in drainage bottoms where temperatures are near 10F.
Today, anCNFAIC Staff calm and warm day is on tap. Skies should be partly cloudy to sunny as clouds are likely to filter in and out. Winds look to be light again, 5-10mph, from the southeast and temperatures should bounce back to the 20’s above treeline and 30’s below.
CNFAIC Weather Page and the NWS forecast
I will issue the next advisory Monday morning. If you get out in the backcountry we want to know what you are seeing. Please send us your observations using the button at the top of this page or give us a call at 754-2369. Thanks and have a great day.