The first in a series of storms is over the region today. Snowfall began yesterday and as of this morning, roughly 2-4″ has fallen with up to 5″ or more in the Girdwood and Placer Valleys. An additional 2-4″ is expected over the course of the day. Although snowfall amounts are meager to what some of us may have hoped for, the winds are producing. Ridgetop winds have been blowing strong from the east (20-30mph with gusts to 50) for almost 24-hours now. The other producer is the temperature. Temperatures have risen as much as 40 degrees F in the last 24-hours. The minus single digit conditions felt in valley bottoms are now in the tropical 30’sF. These are all abrupt changes to the snowpack and avalanche danger has risen.
There was one suspected natural 2′ slab avalanche yesterday in the Johnson Pass/Center Creek area and more of these could occur today. There is very weak snow (sugary facets and surface hoar that formed during our cold/clear period), which will cause any new slab to be very touchy. Watch for shooting cracks and recent avalanches, these are Red Flags that an avalanche will be easy to trigger.
Wind Slabs: With little new snow to work with, the winds will also be transporting the older loose snow surface into sensitive wind slabs. Slabs are likely to be in the foot thick range in general, but could reach as thick as 2-3′ along the tops of ridgelines. They should range from soft to stiff and could be triggered remotely.
Storm Slabs: Warming temperatures are causing an upside-down storm, which will create shallow storm slabs in areas outside of the wind. Again, watch for cracking and carefully evaluate the storm snow.
Cornices: Cornices are growing and the warmth can help weaken them. Cornice falls are possible and may trigger slabs under them.
South of Turnagain – Johnson Pass/Summit Lake zone: As new snow and wind loading increases it becomes even more critical to remember that a poor snowpack structure exists in these areas. The Christmas buried surface hoar has been found as well as concerning facet/crust combinations in the bottom of the snowpack. Avalanches may initiate near the ground and be quite dangerous. If you’re headed this way, evaluate terrain exposure and the snowpack as you travel. Be on the lookout for signs of instability.
Glide cracks are likely to become hard to identify with snow/wind filling them in. Known areas with cracks are the southerly facing slopes on Eddies, Tincan, Sunburst, Magnum, Cornbiscuit, Lipps, Johnson Pass, Girdwood Valley and a few on the easterly slopes on Seattle Ridge. Not to mention the Lynx creek glide extravaganza. Avoiding/limiting time under these features is prudent as they can release into an avalanche at any time and are completely unpredictable. The rapid temperature rise and additional snow load over the next few days may or may not cause an increase in glide activity.
A large glide crack near the head of Lynx creek drainage (seen yesterday 1/12) threatens a popular area to ride.
Yesterday: Overcast skies, light snow showers and rapidly warming temperatures were over the region. Snowfall picked up overnight with 1-4″ accumulating so far – higher amounts seen in Portage Valley and at Alyeska in Girdwood. Ridgetop winds have been strong from the east, averaging 20-30mph with gusts to 50mph. Temperatures rose from single digits to 40F at sea level, 32F at 1,000′ and into the 20’s F along ridgetops over the past 24-hours.
Today: Snow showers should remain over the area today adding an additional 1-4′ with another 1-4″ overnight. Again favored areas are Girdwood and Portage Valley. Temperatures are slated to keep climbing and the rain/snow line may reach 1,000′ by this afternoon and up to 1,500′ by tomorrow morning (#thinkcoldthoughts!). Ridgetop winds will remain strong, 20-30mph from an easterly direction with gusts into the 50’s and 60’s mph.
Tomorrow: Precipitation should continue through Monday with light rain up to 1,500′ and light snow showers above 1,500′. An active weather pattern bringing additional warm and wet weather is expected for the remainder of the week with a possible surge late Tuesday into Wednesday.
*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed. We are currently working to replace it.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||27||2||0.2||53|
|Summit Lake (1400′)||21||1-2||0.1||21|
|Alyeska Mid (1700′)||26||3||0.27||43|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||24||*N/A||*N/A||*N/A|