Turnagain Pass

Another storm has arrived this morning and 6-10” of new snow is expected in the upper alpine in Turnagain Pass. Ridgetop winds have been averaging in the 40s mph with a recent gust to 80 mph from the East Northeast at Sunburst Weather Station. As of this morning several inches of wet heavy snow have fallen along the roadside in Turnagain Pass, and 4″ has been recored at the midway station at Alyeska. Today’s forecast is calling for .7” of water at higher elevations with an additional .3” of water this evening. Rain/snow line will likely move from 500’ to 1500’ as temperatures increase throughout the day.  

This is the second storm to hit Turnagain Pass and Girdwood in the last 48hours. On March 7^th a quick hitting storm brought gale force winds (averaging 40s mph) and dumping 12” of new snow in the upper Alpine of Turnagain Pass and 26” at Alyeska. Today’s storm looks similar with slightly less precipitation expected.

WIND SLABS and STORM SLABS

If strong winds and precipitation amounts reach their potential, wind slabs 10-12” thick could be easily triggered on steep leeward features along ridgetops. At lower elevations protected from winds fresh storm slabs up to 8” thick could be found in steep terrain. On Southern and Eastern aspects triggering a deeper pocket (up to 2’ thick) may be possible where an existing 12” of settled snow is sitting on a sun crust. Today it will be important to let this new storm snow adjust before venturing into bigger terrain. If the sun makes an appearance this afternoon, solar radiation will make slabs more tender and easier to trigger.

A small (D1.5) storm slab was visibile yesterday on Tincan’s Common bowl. This was triggered near the end of the March 7th storm and is an example of storm slab hazard.

 LOOSE SNOW AVALANCHES

Sluffs will likely be a minor concern today, but if the sun appears wet and dry loose avalanches will likely be fast moving and could pick up speed and volume given a large enough slope.

CORNICES

Today’s strong winds and new snow will be adding stress to very large cornices. Natural cornice fall is possible today and thus will be important features to avoid. 

Conservative decision making is essential today and If the visibility improves this afternoonn resisting temptation will be key. it will be important to give large open slopes time to adjust even if obvious signs of instabilty are not present. Don’t forget this is the second new load of snow to fall in the last 48 hours.  

North facing aspects above 2,000′ have a variety of weak faceted layers 3′ below the surface. For the most part these have adjusted to the current load, however with an additional load today (new snow and wind) they have the potential to re-activate. This means either a storm snow avalanche could ‘step-down’ and trigger and deeper slide lower on the slope, or a slab could fail initially in these old weak layers. Either way, Northern aspects harbor potential for large slab avalanches.

If you find yourself hunting for fresh snow after this storm, be aware that a slab avalanche breaking in old snow 3+’ down is possible on steep North facing terrain.