Good morning. This is Chris Engelhardt with the Chugach National Forest Avalanche Information Center on Monday, March 26th 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).
There is a MODERATE avalanche danger for the core advisory area today. Although the snowpack is starting to settle down, the new wind slabs and deeper pockets of fresh snow from Friday night’s storm continue to produce small slab avalanches. These hazards are most likely found on leeward catchment areas above tree line and have been reported on all aspects. The upper snowpack also continues to retain persistent slabs with weak layers such as surface hoar and sun crusts/facet combinations generally found 2-3′ below the surface.
The northern end of Turnagain Pass has seen the most avalanche action recently where there has been numerous reports of shallow, reactive slab avalanches over the course of the weekend. Along with Wendy’s observation from Saturday there were additional public observations on Sunday of 6-12” wind slabs sliding on Southwest aspects in Junior Bowl on Seattle Ridge. Most of these pockets have remained isolated to 50-100′ wide and are generally running 6-800′ vertical if initiated on steeper slopes. Wet loose point releases continue to trickle down southerly slopes in the later afternoon. We have yet to see major wet slab slides on south aspects, but if we continue to get warming temperatures and bright afternoon sun, these will become a much greater concern.
Concern #1 – Wind Slab and Soft Slab
Continue to be on the lookout for fat looking or obviously wind loaded pockets up high. Over the weekend I have found these slabs to extend 20-30 feet downslope just off ridgelines and they definitely feel and sound drummy and hollow. Pay particular attention to cross-loaded areas, where there is a rib, or ridgeline running generally parallel with the main fall line of the slope. These areas in particular seem to be some of the best habitat for tender, lurking, reactive slabs.
Concern #2 – Persistant Slab
Don’t forget that we still have two weaknesses deeper in the snowpack in the form of buried surface hoar and sun crust/facet combinations. We are still finding clean shears at the sun crust around 2-3′ down on south aspects, but these are increasingly harder to make fail. Besides, the skiing and snow machining on sunny aspects is trending towards bad at this point. The buried surface hoar continues to be the little gremlin out there, found in variety of nooks and crannies. Make a mental note of its continued presence, and dig for it 1-2′ below the surface on the cooler shadier aspects. Areas most likely to find this problem are northerly aspects around Girdwood, Placer Valley, 20-mile, and Johnson Pass.
Concern #3- Wet Sluffing
If things heat up, continue to avoid travel on, or beneath sunny aspects. This is especially crucial in the later afternoon. 2-3pm seems to be the magic hour for the south aspects to really start cooking right now.
It was glorious on Sunday and one of the best days of spring 2012 yet. Bluebird sunshine was found all day over the core forecast area. Winds remained very calm yesterday and by 3-4pm temperatures peaked to nearly 30F on Seattle ridge and around 20F on Sunburst. Winds continued to remain calm overnight picking up to around 10mph from the East early this morning. Temps stayed in the 15-19F range for 2-3000 ft elevations on Sunday night. Temperatures are forecast to be WARM today, mid 30’s around 1000ft and it’s anticipated to be partly cloudy to sunny skies with a 30% chance of precipitation. Winds are slated to pick up from the Southeast into the mid 20mph range for ridge tops today.
CNFAIC Weather Page and the NWS forecast
Graham will issue the next advisory Tuesday 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.