Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Tuesday, February 14th 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).
Based on more up to date information this morning, I have bumped the avalanche danger down from high to CONSIDERABLE. Human triggered avalanches are still likely in steep terrain below ridges and rollovers. These will be in the form of soft slabs and appear to be confined to yesterdays storm snow. This storm snow will continue to settle out under a calm atmosphere today.
Once again there is A LOT of new snow in the Turnagain Pass and Girdwood Valley areas, becoming lighter and drier as one ascends into the mountains. With the weather providing a brief reprieve between storms today, I imagine people will be tempted to push into the alpine. Approach this terrain with extreme caution as upper elevation areas experienced significant amounts of snow and wind yesterday. Snowfall at upper elevations in the Girdwood Valley topped four feet (2.5″ of water) with Turnagain pass in the two to three-foot range (1.4″ water at the Snotel). Observations have been limited from theses high elevation areas, but all signs are pointing toward a snowpack that is reaching its tipping point above tree line. I suspect a natural avalanche cycle may be in effect this morning at these upper elevations. Human triggered avalanches will be likely as our snowpack adjusts to this most recent weight. Above tree line it will be quite hard to predict how deep an avalanche may break, as wind slabs have been sandwiched together one on top of anCNFAIC Staff, storm after storm over the last several weeks.
At and just below tree line yesterday, we were able to easily initiate several soft slab avalanches on steep rollovers and gullies. The energy associated with these D1 (relatively harmless to people) avalanches was minimal, meaning fractures were not showing much potential to propagate. This activity was confined to the storm snow (top 18-24″ yesterday) sliding on a bed surface of broken precipitation particles. I expect these soft slabs will be very likely and easy to initiate again today, as we are still well within 24 hours of this latest storm. On bigger, more exposed terrain these soft slabs will have the potential to entrain a significant amount of snow, as surface conditions are extremely loose right now at these mid-elevations.
This latest storm has been deposited on a variety of bed surfaces from slick crusts below tree line, wind slabs above tree line and soft snow at mid-elevations. We found it to have a right side up structure with denser, wetter snow falling early overlain by lighter drier snow. This is good news for this layer to eventually settle and gain strength with its neighbors. We can expect the settlement process to be in full effect today, though this process does take time.
Yesterday’s storm proved short but intense piling up some impressive snowfall totals in our region. Girdwood Valley was the big winner, with storm totals tapering off substantially toward Summit Lake with only a few inches reported in Seward yesterday.
Today is the break in weather everyone has been waiting for. Expect partly cloudy skies and light winds with temperatures right around the 30-degree mark at 1000 feet. This lull in weather will not last as anCNFAIC Staff low pressure is tracking toward south-central Alaska and looks to begin impacting our area as early as this evening.
CNFAIC Weather Page and the NWS forecast
Kevin will issue the next advisory tomorrow 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.