|Travel Advice||Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.||Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.||Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.||Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.||Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.|
|Likelihood of Avalanches||Natural and human-triggered avalanches unlikely.||Natural avalanches unlikely; human-triggered avalanches possible.||Natural avalanches possible; human-triggered avalanches likely.||Natural avalanches likely; human-triggered avalanches very likely.||Natural and human-triggered avalanches certain.|
|Avalanche Size and Distribution||Small avalanches in isolated areas or extreme terrain.||Small avalanches in specific areas; or large avalanches in isolated areas.||Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.||Large avalanches in many areas; or very large avalanches in specific areas.||Very large avalanches in many areas.|
|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|
Well, it looks like March hasn’t yet received Aleph’s letter from Monday…
With another day of clear, calm, and cool weather on the way, and two persistent weak layers in the upper snowpack, today’s avalanche conditions are going to look very similar to yesterday’s. Our main concern is triggering an avalanche on persistent weak layers that formed during late January and early February and are now buried 1-3’ deep. These layers are slowly gaining strength, which means it is becoming more difficult to trigger an avalanche, but it is still possible. We saw human-triggered avalanches failing on these layers at Tincan and near the Girdwood Valley over the weekend, and similar activity will be possible today.
Persistent weak layers require patience and good decision making. Since we have found them at most locations in our advisory area, it is not really reasonable to rule out any chunk of steep terrain as potentially dangerous. So how do you manage a problem like this? Stick with the status quo that we have been talking about for several weeks now– be careful with your route finding and smart with your group management. This means avoiding consequential terrain exposed to terrain traps, only exposing one person at a time to steep slopes, and watching your partners from safe spots.
Wind Slabs: You may still find small and isolated pockets of wind-loaded snow that are capable of avalanching. These are most commonly located below ridgetops, convexities, and in cross-loaded gullies, and will be more likely at higher elevations. Steep terrain with smooth pillows of wind-drifted snow should still be treated with caution today. As mentioned in the bottom line, gap winds today will be building fresh wind slabs around Seward, Lost Lake, Snug Harbor, and the Portage Valley.
Sluffs: Steep slopes that have been protected from the winds now have 2-6” of soft snow on the surface. With continued cool temperatures, this snow is still poorly bonded, which makes it easier to trigger dry loose avalanches (sluffs). Be aware of the potential for sluffs to gain volume and speed in steep terrain, since these can be dangerous if they take you for a ride.
Yesterday: High temperatures reached the mid teens to upper 20s F, with a few hours above 30 F recorded at the Seattle Ridge weather station. Skies were mostly sunny with some thin upper level clouds and a thick layer of valley fog up to around 2200’ that stayed in place until the early afternoon. Winds were light at around 5 mph gusting to 18 mph, with variable direction.
Today: Temperatures this morning are generally in the single digits to low teens F, with the coldest temperatures near Summit Lake at -1 F. Highs are expected in the mid teens to low 20s F, with slightly warmer temperatures near Seward. Northwesterly winds are expected to remain light at 5 mph, with stronger winds near Seward, Portage, and Whittier. Skies will be mostly sunny, with a layer of valley fog lasting until mid day.
Tomorrow: Active weather will start to ramp up late in the day or overnight tomorrow. Easterly winds will be light at around 5 mph for most of the day before picking up to 15 mph in the evening. Skies will be mostly sunny during the day, with clouds expected to move in with the increasing winds in the evening. No snowfall is expected during the day, but chances improve overnight and into Friday. It’s not looking big, but hopefully we will get something out of it.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||13||0||0||113|
|Summit Lake (1400′)||8||0||0||46|
|Alyeska Mid (1700′)||16||0||0||118|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||16||NE||1||8|
|11/27/23||Turnagain||Avalanche: Tincan Ridge||Schauer/ Stiassny Forecaster|
|11/26/23||Turnagain||Observation: Road report: Slide with dirt on Repeat offender||Anonymous|
|11/26/23||Turnagain||Observation: Pete’s North||Ben Sullender|
|11/25/23||Turnagain||Observation: Tincan trees||John Sykes Forecaster|
|11/21/23||Observation: Spokane Creek||John Sykes Forecaster|
|11/19/23||Turnagain||Observation: Magnum – PMS Bowl||Schauer/ Cullen/ Jonas Forecaster|
|11/19/23||Other Regions||Observation: Sunnyside/Penguin||Jose Ramos-Leon|
|11/19/23||Turnagain||Observation: Eddies||Andy Moderow|