After two weeks of warm storms, heavy rainfall to 2,000-2,500′ and an extended natural wet avalanche cycle, cooler air has finally arrived overnight. As of yesterday, the snowpack was still undergoing a wet avalanche cycle below 3,000′. One of the most notable avalanches was a large slab the released naturally just under the CFR ridge on Tincan, pictured below. Other smaller wet slab avalanches occurred yesterday in the Tincan area along with some on Seattle Ridge. Although natural avalanches are still possible, the natural cycle was decreasing yesterday and is on a continued downward trend today. This is due to cooler temperatures beginning to freeze the surface of the wet snow and only light precipitation expected today (1-2″ snow).
Recent wet/moist slab avalanche on Seattle Ridge
Today’s avalanche problems:
Wet slab avalanches below 3,000′ and dry slab avalanches above 3,000′ are our two main concerns, and they are big ones. We have very little information other than visual observations of the snowpack. What we know is very wet and saturated snow exists below 2,500′. Even though a surface crust may be forming with cooler temperatures last night, that will not rule out the possibility of a wet slab releasing today. These wet avalanches are extremely dangerous and even a small one can be unsurvivable. There are no tests that can be done for determining wet slab potential other than a stout refreezing of the pack stabilizing it.
Above 3,000′ moist to dry snow has fallen for two weeks now. Again, we have little information for these upper elevations at this time, but we do know prior to the storm cycle weak faceted snow with crust(s) sat near the ground. The slab on top of this weak foundation has now grown to several feet and much more in places. This presents a deep slab problem and will be guilty until proven innocent. In addition to this, storm slabs, wind slabs and cornices are all concerns in the recent storm snow.
As you can see, for today, conservative route-finding will be essential considering the myriad of avalanche problems and the potential for large avalanches.
Yesterday was a break in the heavy rain and skies were generally overcast. During the morning hours, .6″ of rain fell in the Girdwood Valley and around .3″ at Turnagain Pass before skies cleared. Ridgetop winds were moderate to strong from the East and have diminished overnight, although both the Sunburst and Seattle Ridge weather stations are not reporting we can look to the Max’s mtn wind data to give us an idea. Temperatures that were very warm during the day (mid 40’s at sea level and 30F at 2,500′) have decreased overnight and are sitting near 32F at sea level and the upper 20’s at 2,500′.
For today, Thursday, light precipitation is on the way as a weak low pressure system spins to our East. Forecasted snow amounts are small – an inch for today and another inch for tonight. The good news is temperatures stay cool and the snow line should fall to 1,000′ and possibly lower! Winds should be light to moderate from the North and West today before picking up tonight from the same direction tonight.
Looking ahead, a larger low pressure will bring another round of precipitation Friday afternoon through Saturday. This system looks to wrap in colder arctic air and snow should fall to 1,000′, and possibly sea level. This system may favor East Prince William Sound and snow amounts in our area may be small. Stay tuned on tomorrow’s forecast!
Glimpse of the Tincan meadows
* Sunburst weather station is down due to loss of battery power.
** Seattle Ridge anemometer is rimed and not reporting.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||33||1||0.3||26|
|Summit Lake (1400′)||30||0||0.1||9|
|Alyeska Mid (1700′)||33||3||0.6||19|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||29||**n/a||**n/a||**n/a|
|12/10/19||Turnagain||Avalanche: Tincan and Sunburst from the air||CNFAIC Staff|
|12/10/19||Turnagain||Observation: Tincan||Nancy Pfeiffer|
|12/08/19||Turnagain||Avalanche: Tincan||Ryan Van Luit Forecaster|
|12/06/19||Turnagain||Avalanche: Sunburst||Billy Finley|
|12/04/19||Turnagain||Observation: Sunburst||A.Johnston-Bloom/ W.Wagner/ R.Van Luit Forecaster|
|12/03/19||Turnagain||Observation: Hippy Bowl||Nick Langowski|
|12/01/19||Turnagain||Observation: Tincan, All elevations||Eric Roberts|
|12/01/19||Turnagain||Observation: Tincan||Andy Moderow|
|11/30/19||Turnagain||Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge||Eric Roberts|
|11/29/19||Turnagain||Observation: Sunburst Ob #2||Aleph Johnston-Bloom 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: email@example.com
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