After a week of mostly quiet weather, yesterday ushered in the first – of what looks like a couple – storm systems slated to head our way. Over the past 24-hours the mountains surrounding Turnagain Pass have seen between 8 and 12″ of snow. The storm started out cold with snow to sea level but warm air is arriving and the rain/snow line is now around 1,000′. The cold start to this storm created low density snow and sluffing was the only form of instability seen yesterday. In fact, we had a report of natural sluffs releasing off the Easterly steep slopes near the Byron Glacier trail in Portage Valley.
The low density snow from yesterday is a thing of the past, with a rising rain/snow line and warm temperatures. The 2-3″ of snow that fell last night is expected to be heavy and the additional 6-10″ of snow for today will be even heaver as the rain/snow line is forecast to rise to 2,000′. This is a text-book ‘upside-down’ storm event. This means heavier snow is falling on lighter snow creating a ‘storm slab’ (slab over a weak layer). The weak layer in this case being the light snow from yesterday and slab thickness will depend on how much snow has fallen since last night and through today. This could be anywhere between 5 and 12″. These storm slabs are expected to be on the shallow side at Turnagain Pass but could be much larger in places favored by the storm.
With winds picking up to the 20-40mph range we can expect wind slabs to be forming on leeward slopes. These have the potential to release naturally. They will be thicker than the storm slab, in the 1-2′ range and likely easy to trigger. Travel on wind-loaded slopes is not recommended.
Cornices will be building today and could fall off naturally. Steer clear of slopes, even mellow slopes, under cornices.
Glide cracks continue to be a concern as they may release and avalanche without warning throughout the forecast region. Keep in mind cracks may be buried by the new snow and will be difficult to see. These cracks cover all aspects within the mid elevation band (between 1000-3000’) and remain a significant threat to popular terrain. As long as glide cracks continue to open up, move and release, we will stress the importance of avoiding them.
Photo below is of a glide crack from the Silvertip drainage on Friday, March 18th – credit Billy Finley.
Yesterday, a region-wide snowfall event occurred over most of Southcentral Alaska with the Turnagain Pass area seeing 8-10″ by the late afternoon. Temperatures were cold enough for snow to sea level but have warmed overnight, as of 6am the rain/snow line has risen to ~1,000′ with an additional 2-3″ of snow. Ridgetop winds were light yesterday but have risen overnight as well, averaging 20-25mph with gusts in the 50’s from the East.
Today, the storm will continue. We are expecting another 6-10″ of snow (heavy snow) with a rain/snow line rising has high as 2,000′ (.8″ of rain at the lower elevations). Ridgetop winds should remain strong out of the East averaging 25-40mph. Temperatures are expected to climb to 37F at 1,000′ and the upper 20’sF along the ridgetops.
For tonight, this storm should slowly move out – we could see another 3-5″ at the upper elevations with continued warm temperatures. Monday and Tuesday will be a slight break in weather (light snowfall and breezy winds) before another very large system looks to move in for Wednesday.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||28||8||0.5||139|
|Summit Lake (1400′)||24||7||0.5||50|
|Alyeska Mid (1700′)||27||6||N/A||113|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||22||SE||15||52|
|04/19/21||Turnagain||Avalanche: Triangle, Seattle creek||Will Morrison|
|04/18/21||Turnagain||Avalanche: Turnagain Pass Road Obs||Andy Moderow|
|04/18/21||Turnagain||Observation: Seattle Ridge, approximately 300 yards south of the up track||Brent Byrne|
|04/17/21||Turnagain||Avalanche: Road obs||Johnston-Bloom / Moderow Forecaster|
|04/16/21||Turnagain||Avalanche: Seattle Ridge||Wendy Wagner Forecaster|
|04/16/21||Turnagain||Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge||CNFAIC Staff Forecaster|
|04/16/21||Turnagain||Observation: Sunburst||Lance breeding|
|04/15/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|04/13/21||Turnagain||Observation: Turnagain Pass Road Obs||A Schauer Forecaster|
|04/12/21||Turnagain||Observation: Tincan||Johnston-Bloom / Latosuo Forecaster|
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.