|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
And the next round in a series of storms begins, this time the Kenai Mtns will be favored rather than Anchorage. Snowfall has already started and should peak this evening along with a rapid rise in avalanche danger. From the National Weather Service’s Avalanche Weather Guidance page:
“Two to four foot snow totals are looking likely throughout the mountain ranges of Southcentral …., most of which will fall between Sunday afternoon and Monday afternoon.”
Along the with the feet of new snow, ridgetop winds are going to be howling from the east. Weather models are showing 40-50 mph with gusts near 80, or more by 3pm. It is the textbook case of ‘heavy snowfall plus strong wind = avalanches’. How big the avalanches will be depends on the amount of new snow (1-2′ deep wind slabs by midday) and 2-4′ deep slabs in the overnight hours. The snow will be falling on a mixed bag of surfaces, hard wind packed snow, wind crusts, scoured surfaces to the Thanksgiving crust, and soft loose faceted snow in protected areas. Even if the snow wants to bond to some degree it won’t happen right away with such rapid loading.
For those getting out today, remember the storm will start peaking in the afternoon and know your exit routes. Natural storm slabs and more likely new wind slabs and sluffs should start releasing in the higher elevations by this afternoon. It may not be till after sunset that we see HIGH danger develop in the mid and lower elevations. Nonetheless, this should be quite an intense 24 hours and we don’t want to be caught off guard.
Graphic shows snowfall totals from 6am today through 6am tomorrow – wow!
Wind effect above the Repeat Offender slide path on Seattle Ridge. Photo by Carolyn Spencer, 12.10.22.
In the protected areas (including in the trees) soft faceted snow exists on the surface and by tomorrow morning, there could be some very touchy storm slabs in the trees. There is also a chance older wind slabs and even deeper layers in the snowpack could be overloaded by the storm snow, creating a larger slide. We are watching the old crust formed just before Thanksgiving that in some areas has facets around it.
Snow pit at 2,400′ in the Repeat Offender slide path on Seattle Ridge. Note the softer snow above the melt freeze crusts. We are watching these older faceted layers as they could get weaker as time goes on and become more of an issue – hopefully not. 12.10.22
Yesterday: Overcast skies were over the region with light easterly ridgetop winds (~5mph gusting 10). Temperatures warmed into in the teens at most locations and elevations and have continued to warm near 20F overnight. Light snow flurries developed after sunset.
Today: Light snowfall this morning should intensity by this afternoon and peak tonight. Up to 6″ is expected by noon and another 6+” by 6pm. Overnight we could see a foot, brining snowfall totals to 2+’ by tomorrow morning. Temperatures look to stay near 32F at sea level and 20F in the mid elevations – so snow should fall to sea level through the storm. Ridgetop winds are expected to increase to 40-50mph with gusts near 80 by 6pm.
Tomorrow: Snowfall is expected to taper tomorrow morning as skies begin to clear for the afternoon. Ridgetop winds look to decrease as well and shift northwesterly, blowing 20-30mph.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||18||1||0.1||29|
|Summit Lake (1400′)||13||1||0.1||21|
|Alyeska Mid (1700′)||16||1||0.05||28|
|Bear Valley – Portage (132′)||16||1||0.1||–|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||16||SE||7||20|
|05/22/23||Turnagain||Avalanche: Tincan||Nick D'Alessio|
|05/12/23||Turnagain||Avalanche: Tincan, Sunburst, Magnum, Cornbiscuit||Heather Thamm|
|05/07/23||Turnagain||Observation: Tincan – Bear Tracks||CNFAIC Staff|
|05/05/23||Turnagain||Observation: Seattle Ridge||AS/ WW Forecaster|
|05/02/23||Turnagain||Observation: Cornbiscuit||Schauer/ Sturgess Forecaster|
|05/02/23||Turnagain||Observation: Seward Hwy Turnagain Pass||Joel Curtis|
|04/30/23||Turnagain||Observation: Magnum||Ayla, Kit Crosby, Barton|
|04/29/23||Turnagain||Observation: Tincan||John Sykes|
|04/28/23||Turnagain||Avalanche: Taylor Pass/Pastoral||Schauer/ Creighton Forecaster|
|04/28/23||Turnagain||Avalanche: Tincan||Andy Moderow|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: firstname.lastname@example.org
|Area||Status||Weather & Riding Conditions|
This is 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.