Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Tuesday, February 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).
Lower elevation slopes experiencing less wind effect continue to settle out today with these warm ambient temperatures and increased solar influence. The danger is MODERATE on these slopes, where we can expect to see small moist avalanches releasing naturally today in specific areas around rock bands and trees where solar input is magnified. At mid and upper elevations, the avalanche danger is CONSIDERABLE due to stiff, reactive wind slabs that may be very LARGE AND UNMANAGEABLE.
There has been a significant natural avalanche cycle within the forecast zone over the last 2 days and at least one snowmachiner triggered avalanche on the backside of Seattle Ridge yesterday. Details are limited, but it is believed to be about a 3′ deep wind slab that propagated at least 100′ on a mid-elevation slope.
The primary concern in the backcountry today comes in the form of these stiff, wind slabs at mid and upper elevations. The low-density loose snow that we have all been enjoying for the last several weeks was transformed this weekend (Sunday) into fresh, tender wind slabs at mid and upper elevations. These can be especially dangerous in the backcountry as slopes are accessed from the bottom, luring skiers and snowmachiners onto a slab where a failure has the potential to propagate above you and your party. Pay particular attention to the changes in surface conditions today as you ascend. You will likely find moist, loose snow at lower elevations; a nasty breakable crust at mid elevations changing to wind slab in the likely areas such as below steep rollovers and under ridges. Shooting cracks or collapsing (whumpfing) observed is a tell tale sign that you have found these tender wind slabs.
Lower elevation slopes experienced significant settlement yesterday. Roller balls were also quite prevalent. Indicative of warming surface conditions these form on steep terrain due to high (above freezing) ambient temperatures and/ or solar influence. My guess is that both of these drivers were in play yesterday (and will be again today) on sun-affected slopes. These have the potential to entrain a significant amount of HEAVY and WET surface snow that can step down into deeper layers. Below the top 4-6″ of moist surface snow, you will find our dry low-density powder from just a few days ago.
Yesterday felt a lot like springtime in the backcountry. Partly cloudy skies and temperatures in the mid 30’s at 1800 feet made for gloppy surface conditions. Winds continued from the east, though scaled way back from the gale force experienced on Sunday.
Today we can expect sunny skies and spring like temperatures again. Ridge top winds will continue from the east in the range of 7-20mph. Temperatures look to be warmer today than yesterday topping out at around 38 degrees at 1000 feet. Couple this with direct sun and you will want to put a fresh coat of wax on your skins before leaving the parking lot today. Solar influence will begin to be a bigger player in our forecasts over the coming weeks and months as the trajectory of the sun changes heading into spring.
CNFAIC Weather Page and the NWS forecast
Kevin will issue the next advisory Wednesday 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.