Turnagain Pass

The hopes for a few inches of new snow in our forecast area today is dwindling fast… As seems to be the theme for the past 5 weeks, it is looking like more blow than snow. The front that was heading our way has stalled just to the west and stretching out along Cook Inlet currently. That said, only a few flurries are expected and maybe an inch in a favored location.

The winds on the other hand are a bit of a game changer. Ridgetop weather stations have been steady in the 15-20mph range from the east since 5pm last night with gusts near 30mph. These speeds are expected to decrease throughout the day. A report from the Magnum/Cornbiscuit area at Turnagain Pass described some ‘active wind loading’ beginning around 4pm yesterday. Although these speeds aren’t super impressive, they should be just enough to drift the 4-8″ of existing light surface snow into wind slabs. Slab thickness is likely to be in the 6-8″ range in general and up to a foot thick in the most windy zones.

Fresh Wind Slabs:  The good news is, new wind slabs should be on the smaller side and easy to identify. They are likely to be in the higher terrain above treeline. Watch for areas with recent wind deposited snow and/or active loading. Smooth rounded pillow like surfaces and stiffer snow over softer snow are tell-tale signs of wind slabs, along with any cracking in the snow around you. These should be on the softer side due to the moderate winds. Slabs may be sitting on a fresh batch of surface hoar from the past several days, or on a thin sun crust on steep south slopes, making them a bit easier to trigger in this case.

This table is from the Snow Weather and Avalanche Guidelines and tells us what wind speeds begin to move snow into wind slabs. 

Sluffs:  Steep slopes that have been protected from the winds and the sun have 2-6” of soft snow on the surface and triggering a loose snow avalanche (sluff) is possible.  Remember sluffs can gain volume and speed in steep terrain and can be dangerous if they knock you off your feet and take you for a ride in a high consequence spot.

Soft surface snow over a thin sun crust on a steep south slope.

We continue to track two weak layers of snow (surface hoar and facets) buried in the top three feet of the snowpack. The data continues to show triggering an avalanche in one of these layers remains possible. The layers are present in most areas and at all the elevation bands. The trick is, they are not reactive everywhere. They seem to be more of an issue below 2000′. However, a persistent slab avalanche in upper elevation terrain cannot be ruled out. Triggering a recently formed wind slab or cornice fall may step down to one of these buried weak layers. Additionally, there may be older hard wind slabs sitting on top of the weak layers, allowing a person to get well out onto the slope before an avalanche initiates or an avalanche may occur after other machines or skiers have already ridden the slope. Watch for signs of instability, follow safe travel protocol and evaluate terrain consequences.