Winter is not over in the mountains surrounding Southcentral Alaska! Extra caution is advised at Turnagain Pass. A storm that favored Turnagain Pass overnight brought 9” of new snow. Ridgetop weather stations have reported winds in 15-45mph range with gusts in the 50-60’s mph. In areas that did not see new snow yesterday, 1-2’ of dry low-density snow was available for transport. Expect wind slabs to be 1-2’ in size on leeward terrain features. Shooting cracks and blowing snow today will be an obvious clue that wind slabs are tender.
DRY LOOSE: In areas protected from wind dry-loose surface snow may be easy to initiate and fast moving in steep terrain. Also keep in mind there may be a deeper more dangerous slab lurking under loose dry snow on Northern aspects in alpine.
WET LOOSE: Cold temperatures have caused light dry snow to fall in the mid and upper elevations over the last few days. When the sun appears this is the perfect type of snow for wet loose avalanches. There is potential for late afternoon sun. Monitor surface conditions as you travel and avoid South facing aspects if the surface become wet and sticky.
CORNICES: There are lots of large cornices on ridge tops. These features can heat up with daily warming making them easier to trigger. Give them lots of space.
FRIDAY: Tomorrow looks like the first clear sunny day following the storm. If winds are calm tomorrow and air temperatures increase into the 40Fs, natural wet loose avalanches are possible on South facings slopes.
Recent storm slab on CFR on Tincan yesterday seen just before winds started to increase.
Dry loose sluffs seen on Lipps North facing terrain yesterday prior to winds increasing in the afternoon.
Over the last week 3’ of snow (3.0”SWE) has fallen incrementally in the Alpine of Turnagain Pass and Girdwood. On shaded (NE-N-NW) aspects above 2500’, weak snow may be lurking 2-3’ below the surface. Surface hoar was observed on shaded aspects prior to the last week of stormy weather and facets and buried surface hoar may still be lurking another foot below that layer. The reactivity of this weak snow is unknown, but keep in mind that a 2-3’ thick could have high consequences. Whumpfing and shooting cracks may not be present, and a person or machine may well onto a slope before triggering. Today with active wind loading expected to continue avoiding steep Northerly aspects in the alpine is a conservative choice. Looking into the weekend as snowpack starts to adjust, evaluate terrain for consequences and practice safe travel protocols – expose one person a time, watch partners and have an escape route planned.
* New snow totals vary across our region. Summit Lake has seen around 15” of new snow over the last week. The mountains surrounding Portage Valley and Whittier have seen up to 5’of new snow.
Several new glide avalanche were observed in Turnagain Pass yesterday – one on a SE aspect of Seattle Ridge and the other on a SW aspect of Eddies. Glide cracks are continuing to creep open and still exist in many popular areas of Turnagain Pass. As always identify cracks and avoid traveling under their runout. They are unpredictable and can avalanche at any time.
Yesterday: Skies were broken in the morning becoming obscure by early afternoon. Ridgetop winds were 10-45mph from the East and strongest overnight. Sunburst weather station recorded the strongest winds 30-40mph with gusts in the 50-60s mph. Turnagain Pass received 9″ of new snow in the last 24 hours. Temperatures were in the low to mid 20Fs in the Alpine. Near sea level temps were 30-40F. Rain/snow line was around between ~400′.
Today: Skies will be overcast with a possibility of broken skies in the afternoon. Scattered snow showers should diminish by late morning. Easterly ridgetop winds 15-25mph will start to decrease in the afternoon to 5-15mph and shift to a NW direction. Temperatures at sea level will be in the low-30Fs to mid-40Fs. Temperatures in the upper elevations will be in the 20Fs with a high near 30F. Overnight temperatures are expected to drop below freezing at all elevations.
Tomorrow: Clear and Sunny skies are in the forecast for Friday and through the weekend. No precipitation is expected. Northwest ridgetop winds are expected to be light, 5-10mph. Daytime temperatures at sea level could reach the upper 40Fs to low 50Fs. Daytime temps in the alpine may reach the mid to upper-30Fs. Freezing temperatures are expected overnight.
*Be aware that Seattle Ridge weather station may be under-reporting average wind speeds and gusts.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||30||9||0.7||81|
|Summit Lake (1400′)||33||0||0||19|
|Alyeska Mid (1700′)||30||trace||0.02||67|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||ESE||*8||*21|