Turnagain Pass Avalanche Forecast

Temperatures dropped and winds shifted to an outflow pattern last night.  With this northwesterly wind came an increase in wind speeds and gusts are expected to build to the 30-40mph range. There is soft snow available for transport. If these wind speeds materialize today it could become likely for a person to trigger newly forming wind slabs. Terrain along the Arm and south of Turnagain Pass are often impacted the most by these winds and natural avalanches will be possible. Turnagain Pass is often spared by this wind direction but it will be important to pay attention blowing snow and changing surface conditions.  There may also be older wind slabs that formed over the past several days. These wind slabs could be 1-2′ thick and will most likely be found in Alpine terrain on loaded slopes just off ridges and in cross loaded gully features.  A lingering concern is whether or not wind slabs remain reactive due to a layer of buried surface hoar.  Signs of this unstable snow include features with hard snow that looks loaded or pillowed, cracking or collapsing, or feeling hard snow over a softer layer.

A example of outflow winds which we expect to build throughout the day today.  If you see windloading, the avalanche danger is likely increasing.  Lost Lake region.  Photo: Alex Mc Lain

Cornices:  Avoid travel on cornices and limit exposure underneath them.

Loose snow avalanches:  In areas that were protected from the wind, sluffs are possible in steep terrain.

Sun effect: Even with cold temperatures the sun may impact surface snow on steep solar aspects.  Be aware of moist surface snow, small roller balls or loose snow avalanches in wind protected spots, especially below steeper rocky areas.

The snowpack structure for this avalanche problem still exists and an outlier avalanche could be a nasty surprise. There is nagging worry that someone will hit the wrong spot and trigger a very large avalanche that fails on the weak faceted snow from January. This is still lurking 3 to 6 feet deep in the snowpack. The wind slab triggered in Lynx Creek last Thursday was a larger avalanche because it ‘stepped down’ into these old weak layers. As time passes the likelihood of triggering a deep slab is decreasing, i.e. is unlikely. Areas that have a shallower snowpack are more concerning, places like Lynx Creek or Twin Peaks and south through Summit Lake.  As always, use good travel protocol and as you choose your route consider the consequences if a deep slab was triggered.