Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Saturday, April 7th 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).
We continue to have a MODERATE danger today for two distinct problems in specific areas: 1- Slab avalanches failing on buried surface hoar remain possible to trigger above treeline on northerly aspects where dry snow exists. 2- Wet avalanches are possible at the lower elevations, below 1000′, in areas where saturated snow has not refrozen, for example, Placer Valley and 20-mile. CNFAIC Staffwise, there is a LOW danger at the mid elevations and on slopes sporting supportable crusts.
Those who ventured into the backcountry yesterday were greeted with clearing skies and sunshine. This along with warm temperatures has either glued Thursday’s shot of 4-6″ of dense snow into place, or added water to the wet saturated snow below 1000′. Most surfaces above 1000′ became damp or wet yesterday and have likely refrozen overnight. Expect areas below 1000′ to have a shallow or no refreeze. Dry snow still exists in the upper alpine on northerly aspects – the EXACT location where people are still able to trigger slab avalanches. One person did find one of these slabs on Sunburst yesterday.
We have a possible inch or two of new snow on tap today with light winds, which could improve riding conditions, but is not expected to impact the avalanche danger.
Above treeline – Persistent Slab and Wind Slab
Our primary concern today is back to the buried surface hoar that is now 11 days old (buried March 27th). This layer is 8-16″ deep and continues to produce human triggered avalanches, as was seen yesterday. Additionally, snow pit tests consistently show this layer is still reactive, but becoming harder to trigger. Upper elevation northerly aspects that harbor dry snow is the place to find one of these slabs. These have been small to medium in size, 30-100′ wide, and around a foot deep.
Wind slabs that formed during Thursday’s 4-6″ ‘dump’ may still be possible to trigger on the high alpine peaks sporting dry snow and colder temperatures. However, from observations yesterday near 3000′, these had settled out and were glued well into place.
Below treeline – Wet Avalanches
With off and on light rain and warm temperatures that we have seen for the past 3 days, slopes below around 1000′ are saturated and soggy. These lower elevation areas, for example in the Placer Valley and 20-mile, that have not seen a refreeze to lock and stabilize the snow, have the potential for a person or snowmachine to initiate a small wet sluff that can become quite dangerous quickly. This is mostly likely found in steeper terrain, near valley bottoms, that funnel into gullies where sluffs can entrain additional wet snow.
Glide Avalanches and Cornices
Countless glide cracks are inching their way wider with our warming temperatures. Though these do not always release and avalanche, if they do, their destructive power can be great. It is best to not eat lunch or hang out under these. Also, cornices are beginning to pull away from the ridgelines and deserve a wide berth.
It turned out be a nice, mostly sunny day yesterday with a few lingering high clouds. Temperatures climbed to the mid 20’s on the peaks, mid 30’s at 2000′ and mid 40’s at sea level. Winds have calmed down but were still a bit breezy on the ridgelines, blowing ~10mph with gusts near 20mph.
Overnight, temperatures had a hard time dropping with cloud cover moving in and, what looks like, an inch or two of snow falling in the Girdwood Valley with only a trace on Turnagain Pass. The southeast winds have remained around 10mph with gusts in the low 20’s, where they are forecast to blow during the day today. There is a chance we may see an additional 1-2″ of snow through the day with the rain/snow line around 900′. Temperatures are forecast to be in the mid to upper 30’s at sea level, near 30 at treeline and low 20’s on the ridgetops.
CNFAIC Weather Page and the NWS forecast
Chris will issue the next advisory Sunday 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.