Clear skies following a big storm is a red flag warning for human triggered avalanches. Over the last three days rain, snow and strong winds impacted our region with an additional 2-3’ of snow in the upper elevations on top of 2-3’ that fell over the weekend. Rain/snow line reached around 3000’ on Tuesday and slowly dropped to ~1300’ yesterday morning as temps cooled near the end of the storm. There was a widespread natural wet avalanche cycle observed on Tuesday in steep channelled terrain from Girdwood to Summit Lake.
STORM TOTALS above 2,500′ (1/15-1/17)
Turnagain Pass 20-30″ (2.3” of snow water equivalent)
Girdwood Valley 20-30” (2.1” of snow water equivalent)
Summit Lake 6-10” (0.6” of snow water equivalent)
Don’t Forget!!! This was the second storm in one week. Basically 4-6+’ of snow is sitting on old weak surfaces (surface hoar and facets) from last week. In between these two storms, several human triggered avalanches occurred on Seattle Ridge and Eddies, without incident, and stability tests were showing propagation potential in older layers of the snowpack. More time and lots of patience is required for all of this new snow to adjust. If you are headed out – keep these points in mind
Dry snow is covering and insulating a wet layer of snow within the new storm snow. Until this wet layer freezes, triggering an avalnche will remain possible in mid elevations.
Most of the gullies along Seattle Ridge are full of new debris from a wet snow avalanche cycle that occured on Tuesday.
Weak layers within the snowpack have the potential to re-activate with the added load of this week’s new snow (5” of water weight). Additionally, avalanches in the storm snow, discussed above, could step down to these deeper layers and produce a very large avalanche depending on the size of the slope. In short, two layers of buried surface hoar and near surface facets sit roughly 4-8’ deep at this point and is a concern at elevations above 2,000′. Basal facets, near the ground, remain a concern at elevations above 3,000′. At this point very little is known about reactivity of these weak layers, and its going to take time and patience for the snowpack to adjust.
*Giving the snowpack time to heal from these storms is key. Sticking to low angle terrain with nothing steeper above is recommended. Remember, it’s the first 2 days after a storm where most avalanche fatalities occur. Although there is nice powder at the upper elevations that can lure us, now is not the time to be sampling it.
A natural avalanche near Bertha Cr on the Southern end of Seattle Ridge (SE aspect) that broke into older layers of the snowpack.
Cornices have been growing and were unstable in between the two storm cycles this week. Triggering a cornice is likely if you get too close. A cornice fall could trigger a very large avalanche on the slope below. Give these features lots of space and remember they can break further back from a ridge than expected.
Yesterday morning a potent storm ended with a cooling trend. Freezing temps (32F) creeped down in elevation, and rain/snow line moved from around 3000′ the night before to ~1300′ by late morning. The most intense precipitation ended by 6am yesterday, but rain and snow showers were observed throughout the region most of the day. No measurable amount was recorded at Center Ridge weather station, but .25 € was recorded at the Turngain Pass DOT Lot. Girdwood midway station picked up ~.3 € of water late morning, which fell as a few inches of heavy wet snow at 1700′. Easterly ridge top winds were moderate, averaging in the 20-40mph becoming light by early evening. Overnight Satellite images indicate clearing skies and temps dropped to mid 20F’s 1000′ at Turnagain Pass.
Today expect clear skies, temperatures in between 20-30F and light Northerly winds. No precipitation is expected.
Cold and clear weather is expected over the next two days as high pressure from Siberia settles in over interior Alaska.
**Seattle Ridge weather station stopped recording wind data yesterday evening due to rime forming on the anemometer
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||29||0||0||56|
|Summit Lake (1400′)||29||0||0||15|
|Alyeska Mid (1700′)||30||3||0.3||42|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||27||**SE||**7||**31|
|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|
|11/29/19||Turnagain||Observation: Sunburst Ob #1||Aleph Johnston-Bloom Forecaster|
|11/27/19||Turnagain||Observation: Tincan||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: firstname.lastname@example.org
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