Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Thursday, April 5th 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 have a MODERATE avalanche danger today for newly formed wind slabs above treeline due to an expected 2-5 inches of new snow with strong winds. These are most likely to be shallow and found on south, west and north slopes. Careful evaluation of these fresh slabs is necessary as they are expected to be touchy and in some areas could be deep enough to take you for a ride. Additionally, there is a MODERATE danger for wet avalanches below treeline where rain on snow below 800ft, and wet snow below 1500ft, will keep human triggered avalanches possible. In the small chance snow accumulation should dramatically increase, nearing a foot, the danger will rise to CONSIDERABLE.
The cool, cloudy and breezy conditions we saw yesterday kept much of the snow surface from warming and essentially shut down wet activity on south and westerly aspects for the first time in several days. Slopes at the upper elevations having a northerly tilt continued to hold soft settled powder and/or wind crusts. These slopes also continue to harbor buried surface hoar, yet it is has been a couple days now since we have heard of anyone triggering a slide on these layers.
Above treeline – Wind Slab, Soft Slab and Persistent Slab
With what looks to be 2-5 inches of new snow today, coupled with strong (30-40mph sustained) winds, fresh wind slab and/or soft slab avalanches will be our primary concern. These new slabs are expected to bond poorly as they are forming on a variety of slick surfaces including, sun crusts on southeast through southwesterly slopes and wind hardened to soft settled powder on northwest through northeasterly slopes. All of these surfaces were covered with surface hoar yesterday. The good news is, the warm temperatures and wind began breaking down the surface hoar in some locations, but this is not likely the case everywhere, increasing the expected poor bonding. The modest amount of new snow, with very little existing snow available for transport, will keep slabs fairly shallow.
Upper elevation northerly aspects still have at least one, if not more, layers of older buried surface hoar that is still reacting and propagating in pit tests. These are generally in the top 3 feet of the pack and becoming harder to trigger. It is possible that a smaller avalanche could step down and break into these layers turning a manageable 6 inch soft slab into a more dangerous 2ft deep slide.
Below treeline – Wet Avalanches
With rain expected to fall on snow below 600ft and wet saturated snow below ~1500ft, wet avalanche activity is worthy of mention. Though this storm is not looking to be wet or warm enough to really get things going and the pack below 1500ft is becoming seasoned for warmer and wetter conditions, human triggered slides remain possible.
Yesterday, our brilliant sunny skies gave way to thick clouds as a storm system spinning in the Gulf moved in. Light snow began to fall in the late afternoon and easterly winds picked up, blowing 10-15mph gusting to 25. Temperatures during the day remained in the mid 20’sF above treeline and mid 30’s below.
Overnight, 1-2 inches of snow has fallen in Turnagain Pass and Girdwood Valley while stations in the Summit area are reading no accumulated precipitation. We should see anCNFAIC Staff 1-4 inches through the day for a total of .5″ of water equivalent by this evening. The rain/snow line is hovering around 100ft and should rise through the day to near 800ft. Temperatures that are sitting in the mid 30’s at sea level and mid 20’s at 3000ft are forecast to rise just a few degrees during the day. Easterly winds increased overnight, blowing 30-35mph with gusts to 50mph, where they are expected to continue until this evening.
Tonight through Friday, snow showers may persist but wind should tapper off. We may see an additional few inches, possibly more, to help freshen the riding conditions for the weekend.
CNFAIC Weather Page and the NWS forecast
Chris will issue the next advisory Friday 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.