Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Tuesday, February 28th 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).
Our upper snowpack continues to show signs of settling and strengthening. Storm snow from Sunday and Monday morning seems to be bonding fairly well with the underlying layers under a calm atmosphere today. The danger today is MODERATE for Loose snow avalanches and sluffing in steep terrain.
As this latest storm wound down yesterday afternoon, the clouds broke allowing us a brief look around the alpine. The most striking observation was felt (rather than seen) yesterday as a complete lack of wind at ridge top levels. This can be better understood taking a look at our Friends weather station page.
Surface conditions were a consistent 12-20″ of light to medium density snow on top of a slightly denser wind slab, showing the right side up structure that makes for a stable snowpack. We were not able to get any notable results at this storm interface yesterday. Additionally, this most recent storm snow layer is showing low energy, meaning a crack is unlikely to propagate from an initial fracture. This is good news, as our upper snowpack will continue to gain strength through today and tomorrow under a relatively calm atmosphere.
Our primary avalanche concerns today lie in the form of loose snow avalanches and sluffing within this latest storm snow. This concern is to be expected on steeper terrain where a skier or snowmachiner has the potential to entrain a significant amount of loose snow while descending. Furthermore, these sluffs are running further and faster than you may think as this new and relatively dry surface snow becomes entrained, building in mass. If you expect this loose snow activity in steep terrain, you can mitigate the hazard and be rewarded with some really fun, steep skiing today.
A secondary concern that warrants mention is the fact that spatial variability and anomalies do exist in our snowpack. Alaska Railroad, DOT and Alyeska Ski Patrol all conducted avalanche control work yesterday with varied results. A lot of explosives were thrown at our mountains, most not producing any results. However, when the sweet spot was found crews were able to produce class III and IV avalanches in isolated terrain as seen in this video from Kern creek yesterday. These were undoubtedly sizeable triggers, but beware that large avalanches are possible today if one were to find the sweet spot.
Snowfall in Turnagain pass and the Girdwood Valley tapered off yesterday around 3pm leaving anCNFAIC Staff 4-8″ of light density snow on top of the Sunday storm. Winds have been almost non-existent at ridge top levels for more than 24 hours now.
We can expect a mild day of weather on tap for today with winds unlikely to break the 10mph mark. High clouds will dominate our area as a weak stationary low lingers over the south-central region today. We may squeeze an inch or two of snow out of this system as it moves through, but accumulations will be insignificant. Expect temperatures in the mid-20’s today at 1000′, becoming colder as you ascend into the mountains.
CNFAIC Weather Page and the NWS forecast
Kevin will issue the next advisory Wednesday 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.