Three avalanches were reported recently.
One was triggered yesterday by a snowmachine at the top of the archangel trail by the old Lane hut location with no involvement, one was triggered by a skier near Friendship Pass which included a partial burial but no injuries, and one was natural which likely occurred during the 1/23-24 storm in the Rock Garden/Pinnacle Valley.
This picture shows the nature of the recent January warm storm’s ability to glue snow to very steep rock faces. It is rare for these peaks to not be showing rock.
While we are well into the winter and headed into the Spring snow season in Alaska, we still don’t have that much of a base. At least three snowmachines were damaged yesterday due to impact with buried rocks. Smasher’s Pass needs more snow for snow machining, but for skiers, boarders, and snowshoer’s it is uncommon to be hitting rocks on most slopes above 2500′.
|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
It’s now been 7 days since the 1/23 storm which dropped 1.4″ of water in about 8″ of snow and 3 days since the 1/25 storm which dropped 0.4″ of water in about 2-3″ of snow at 3550′. These back-to-back storms brought about 10-11″ of warm dense snow which has bonded fairly well to the old December widespread wind-packed firm surface. Winds associated with these storms drifted the new snow onto West to North aspects and terrain features, up to approximately 18″ deep.
The December wind-packed snow is highly variable in thickness, to non-existent. Additionally, the 1/23-26 new snow was wind scoured and drifted. This makes for a complicated weak layer problem that varies in continuity across aspects, slopes, and terrain features.
There are specific locations where triggering an avalanche is still possible. Picking out exact problem locations will be difficult.
Expect the new snow to fail above the old December wind packed firm snow on a thin layer of rounded facets, or just below that in a layer of faceted sugar snow. Yesterday’s avalanches appear to have failed at the 1/23 interface of newer snow over the December wind-packed snow. The video below shows exactly this situation.
Our instability tests have shown some variability and some have shown propagation. Both our data and recent avalanches are consistent and confirm that small to large human-triggered soft slab avalanches are possible in specific locations up to 18″ deep.
Numerous people were in the backcountry yesterday, recreating on steep slopes, and did not trigger avalanches while a few did. This information is useful and somewhat representative of stability but needs to be taken with a grain of salt.
It’s important to note that we have not been experiencing whumping and cracking, and people who have triggered avalanches also did not experience this warning sign prior to triggering avalanches.
In order to increase your safety, employ rigorous travel protocol and be prepared for companion rescue.
Below is a snowpit on the SW aspect of Marmot that demonstrates the snowpack has strong strength, but once that strength is exceeded propagation is present in failure and avalanches are possible. There may be weak points in the snowpack due to spatial variability we can’t readily see, and it may be the 2nd, 3rd, 4th, etc person who finds the trigger point and triggers an avalanche. Tracks on a slope are not a sign of stability with this avalanche problem. Take the snowmachine triggered avalanche near the old Lane hut location for example, it was the second rider on that slope who triggered the avalanche. See pictures above in recent avalanches.
Overnight IM Snotel did not show any measurable precipitation. Frostbite Bottom Snotel reports 0.1″ SWE, however, the Skeetawk snowboard inn close proximity to the Frostbite Snotel showed nothing.
The next best chance for snow after this morning’s possible trace is Sunday for up to 1″.
Avalanche Weather Guidance
National Weather Service Anchorage AK
339 AM AKST Sat Jan 28 2023 .
DISCUSSION…A strong upper level ridge will remain over Southcentral and the Gulf of Alaska through Sunday, then weaken and begin to shift a bit to the east Sunday night through Monday. Warm air moving up and over the ridge has started to move into Southcentral. A near continuous very gradual warming of temperatures aloft will continue through tonight, especially along the Kenai and western Chugach Mountains. Some spotty light precipitation is possible today, with rain, snow, and freezing rain all possible, depending on location. In most cases it will not be measurable precipitation. The one exception is the western side of the Talkeetna Mountains (including Hatcher Pass) where some very light snow accumulation is possible. A series of weak upper level short-waves riding up the west side of the ridge will arrive in Southcentral Sunday afternoon through Sunday night, bringing widespread light precipitation. Temperatures will cool and snow levels will begin to fall as the atmosphere becomes saturated. Generally expect snow levels to settle somewhere in the 800 to 1500 ft range. Freezing rain will also remain a threat into Monday for lower elevations.
NWS AVG Forecast here.
NWS point forecast here.
Marmot Weather Station here.
Independence Mine Snotel here.
Frostbite Bottom Snotel here.
State Parks Snow Report and Motorized Access information here.
XC trail grooming report for Mat-Su, Anchorage, and Kenai here.