Turnagain Pass

After a brief break between storms, another system is literally on the doorstep. This one is characteristic of a Classic Chugach Storm – warm, wet and windy. Opposed to Tuesday night’s storm which was cool and calm; meaning 1-2+ feet of new snow fell with relatively light winds. Avalanche activity yesterday consisted of many natural and remotely triggered storm slab avalanches in the Girdwood Valley and Placer Valley where over 2 feet of snow fell. Observers noted significant propagation with these slabs which points to the fact the new snow is sitting on weak old snow. In general, visibility was very hampered and at Turnagain Pass where only a foot of new snow fell, only one natural avalanche was seen on Tincan’s Southerly face under Hippie Bowl. 

As of 5am this morning winds from the East are just ramping up – expected to average in the 25-40mph range. Snow is expected to begin later today with 2-6″ forecast by 6pm and another 6-12″ forecast tonight. The strong winds will be the main contributing factor to avalanche activity today, yet there are other avalanches issues present. The whole run down is:

WIND SLABS and CORNICES:
Strong winds today should have an easy time moving yesterday’s new snow around and loading leeward slopes, creating large wind slabs and cornices. These are likely to release naturally and could entrain enough snow to run quite far. In areas such as Portage Valley where over 2′ of new snow has already fallen, these slabs could run to sea level.

STORM SLAB AVALANCHES:
In areas out of the wind, expect the recent storm snow to still be touchy. Where up to 2 feet of new snow has already fallen, such as Girdwood Valley and Placer Valley, human triggered slab avalanches 1-2′ thick are still likely, as was the case yesterday. At Turnagain Pass, with only a foot of new, shallow slabs and sluffs are possible.

LOOSE SNOW AVALANCHES:
Sluffs in the new snow should be expected on all aspects and elevations – this issue is overshadowed however by the much more concerning avalanche problems mentioned above.

All this said, with the active weather over the region, travel is avalanche terrain is not recommended. Sticking to the flats, well away from runout zones, heading to the local ski hill or filing your PFD/doing taxes are all good options for the next few days!

Five Sisters slide path in the Portage Valley. Skies opened just enough to see several crowns 2-3′ thick in the recent storm snow; hard to see in the photo. Fresh debris did not run to the valley floor, only part way down over the older debris.

14″ of new snow sits over facets on North aspects (photo below) and a sun crust (.5 – 1″ thick) on Southerly asepcts at Turnagain Pass on Tincan.

Satellite image from 6:00 am (infrared image) of the large low-pressure headed our way today and forecast to churn warm, wet and windy weather in the region through the weekend.

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Don’t forget that our snowpack harbors several old layers of weak snow. Avalanches releasing in the storm snow have the potential to ‘step down’ into these layers. Furthermore, as the new snow piles up and begins to stick to the old snow surface, avalanches breaking into them is possible as well. Both of these situations can create a much larger avalanche – something to look for in the coming days.