The mountain snowpack was tested yesterday with Mother Nature’s violent shake down. The Nov 30th 7.0 earthquake rocked the region. Luckily visibility was good enough to get eyes on some of the aftermath. Girdwood Valley was the most exciting as large slabs were triggered along with rock fall. Turnagain Pass fared better, as most the snowpack stayed intact. The most notable slabs on Turnagain were on the east facing slopes of Twin Peaks. Otherwise there were some shallow slabs on the southern end of Seattle Ridge and small cornice falls along ridgetops.
What does this say about the snowpack? Well, the storm snow from last weekend that fell on buried surface hoar (a weak layer) and in some areas old weak snow, is definitely adjusting – the snowpack did not totally shake off the mountainsides. One can deduce that triggering a large avalanche is becoming less possible. Despite this, keeping in the forefront of our minds that a weak layer sits 1-3′ below the snow surface is still essential. Safe travel protocols and watching our partners shouldn’t be forgotten. Additionally, any signs telling us a slope could be unstable are not likely to be seen.
Earthquake triggered avalanches in upper Goat Mt and Goat Couior in the Girdwood Valley
Magpie Peak in the upper Crow Creek Valley – avalanche debris and some slabs seen triggered by the earthquake
Rock fall off peak 4710′, north aspect
Rockslide off the east face of Rainbow Peak in Chugach State Park – triggered by earthquake
Winds are slated to bump into the 40’s mph today from a southerly direction along the ridgetops. This is an unusual flow direction. Watch for terrain forcing to shift winds either westerly or easterly. Be on the lookout for how winds may be transporting snow and avoid any fresh wind drifts or slabs that may form. Above 2,500′ there is loose snow available for transport plus a possible 1-3″ of snowfall today.
Yesterday: Partly cloudy skies were over the region with a few snowflakes falling last night, adding a trace. Temperatures have been steadily in the 20’sF and teens at the high elevations. Light and variable winds yesterday turned easterly overnight, with a bump in speed to 15mph with gusts to 30mph.
Today: Light snowfall with 1-3″ accumulation is expected today before diminishing tonight. Temperatures should rise significantly, turning snowfall to rain as high as 2,000′ by the afternoon. Cross your fingers the cool air stays in place! Winds are forecast to increase up to 40mph from the SW with stronger gusts, also diminishing to the 15-20mph range tonight.
Tomorrow: Another band of precipitation is expected to move through tomorrow. This one is expected to be cooler, bringing a chance for a few inches of snowfall to lower elevations.
*Seattle Ridge wind sensor is rimed over.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||26||Trace||0||10|
|Summit Lake (1400′)||26||1||0.1||1|
|Alyeska Mid (1700′)||27||Trace||0.03||0|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||23||*no data||*no data||*no data|