Why you should still be concerned about PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW): Variable snowpack depth, hard slabs, persistent weak layers, and slopes that haven’t slid. The likelihood of triggering an avalanche is decreasing but depending on the specific slope the consequences could still be high. Things to remember today…
1) Its been 5 days since a big wind event loaded Northern aspects and cross loaded many Eastern aspects. This wind event as well as the Christmas snow storm caused widespread avalanching in the area. Avalanches were 1-3′ deep and large enough to kill or injure a person. Slopes that did not slide in either event should be approached with caution. Always consider how large a slope is and what other terrain it is connected to. Triggering a slab from below is still possible, especially on a snowmachine.
2) Several persistent weak layers are buried within the snowpack (facets and buried surface hoar), but strong supportable snow over top is making it stubborn to trigger. The snowpack depths across the advisory region are variable. In the areas where a thinner snowpack exists several observers have experienced collapsing/whumpfing in recent days. Including an observer who felt/heard a loud collapse followed by a fast moving shooting crack on their second ascent up Max’s Mountain on Sunday. It may be easier to find unstable snow in these areas. The tricky part is that obvious signs like cracking and ‘whumpfing’ are becoming less common in the Turnagain Pass area and may not be an early warning sign that a slope is still dangerous.
3) Look for hard snow over soft snow – slabs can be strong enough to support the weight of a snowmachine or skier, allowing you onto them before they release. It could also be the 1st or 5th or 12th person or machine on the slope that tips the balance. Slabs on unsupported slopes in steep rocky terrain are prime suspects. Thin spots in the slab are likely trigger points. Always practice safe travel techniques in avalanche terrain.
Wind slab that propagated in a snow pit yesterday on Eddies on a Northerly wind loaded aspect.
Avalanche on Magnum from the 12.30.16 wind event. Example of slide with high consequences and adjacent slopes that may still harbor a dangerous snowpack.
The warm, above freezing temperatures at the ridge tops for over 36 hours is unusual. The snowpack has been settling steadily due to the temperatures and the Tincan Snow Profile Monitoring is showing that the snow near the surface is gradually warming. However, radiation is minimal at this time of year, no melting has been observed and clear nights with low humidity have allowed for radiant cooling. What does this mean for you traveling today? Probably not much but there is a chance that the settlement and warming have affected the slab character and could make triggering a little easier.
Yesterday was mostly clear in the morning with high clouds moving in during the afternoon. The inversion was in place again with valley fog and temperatures remaining above freezing in the alpine. Seattle Ridge again measured 40 degrees F a couple of times throughout the last 24 hours and has been recording above freezing since Sunday. Temperatures in the valleys were in the single digits to low teens. Winds were light and westerly.
Today some high clouds may still be around but skies should be mostly clear. As the day progresses cooler air should filter in and help break up the inversion. Temperatures should be in the 30s at ridge tops and in the teens in the valleys. Winds should start out light and westerly but get stronger throughout the day and shift to the NW.
Tonight and tommorrow colder temperatures, clear skies and strong NW winds are on tap as a series of cold short waves from the Arctic move over the region. Winds are forecasted to really increase through the day tomorrow into the evening and continue through Friday. Temperatures should drop into the teens and low 20Fs. The pesky blocking ridge is still the main influence on the weather until sometime early next week. Expect much of the same weather throughout the weekend.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||33||0||0||36|
|Summit Lake (1400′)||14||0||0||11|
|Alyeska Mid (1700′)||28||0||0||24|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||38||NNW||4||13|
|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|
|11/29/19||Turnagain||Observation: Sunburst Ob #1||Aleph Johnston-Bloom Forecaster|
|11/27/19||Turnagain||Observation: Tincan||Aleph Johnston-Bloom Forecaster|
|11/25/19||Turnagain||Observation: Sunnyside||Graham Predeger 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|
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