Hatcher Pass

Recent Avalanches (apologies for grainy low light photos)

Update 12pm 4/13

Several large D2-2.5 avalanches have been confirmed today at Hatcher Pass including Marmot, Divide Ridge off of Idaho Peak, and the Punk Spines. We expect that numerous other avalanches have occurred but visibility has made observing them challenging. One avalanche on Vice Presidents of Marmot and a second avalanche in Marmot gully 2 have hit or crossed the road recently.

Occurred late Wednesday night, Vice Presidents of Marmot. Partially crossed the road with approximately 15 ft of debris. Photo: K. McGrath

4/13 Divide Ridge on Idaho Peak, Natural storm slab. Photo: K. McGrath

4/13 Punk Spines on Arkose Ridge. Looks like natural wind slabs mid storm but hard to tell with low light. Photo: K. McGrath

Numerous dry and wet sluffs were reported or observed on all aspects this week.

A few small slab avalanches were reported this week. See obs from Goldmint here. 

4/7 4900′ WNW 2 mile creek up Goldmint. Human triggered slab avalanche

4/7 Sluff debris from peak 5100

Due to a lack of visibility on Wednesday we could not see any recent avalanches that we expected to occur during and after the 4/11-12 storm.

Hatcher Pass has received 30″ of new snow with 2.5″ SWE at 3550′ over the last 48 hours. During most of this storm HP received 1 inch per hour which is significant and will easily overload the existing snow structure.

Large to very large STORM SLABS will be very likely to human trigger today on all aspects, at all elevations, on slopes steeper than 30º.  Expect avalanches to be larger on southerly aspects, southeast to southwest, where numerous buried firm crusts will act as a smooth bed surface. Natural avalanches are likely today.

The structure of the snowpack is poor on southerly aspects. Until now, frozen crusts have been holding it together. However, we expect this storm to overload weak layers, resulting in numerous avalanches. It will be possible for storm slabs to hit or cross the upper road off of Marmot between mile 16 and Archangel.

Travel in avalanche terrain is NOT recommended today. 

Limited visibility inhibited our ability to see any terrain on Wednesday, however, we did observe shooting cracks and new storm slabs that gained density throughout the day due to the greenhouse effect from the clouds. Low density snow in the morning quickly moistened by the afternoon and glopped to your skis and boots below 3200′.

Mile 15 webcam snowing steadily at 2am and contributing to the avalanche problem.

Shooting cracks and cohesive slabs observed at 3000′ on Wednesday.

To identify storm slabs use hand pits, small test slopes, and stability tests.  Recent avalanches, cracking and collapsing will be red flags for this avalanche problem.

Wind slabs 6-12″ thick will be likely to tigger on leeward aspects, W to NE, at mid and upper elevation, on slopes steeper than 35º. Wind slabs will be unlikely to trigger at low elevation where winds have been relatively calm.

At 4500′, winds have been gusting SE>S>SW 17-26 mph intermittently over the past 48 hours with consistent gusts in the teens.  Additional new snow accumulation combined with lack of visibility throughout the day will disguise wind slabs that have formed and make identifying them challenging to impossible today.

To identify wind slabs look for hard snow sitting over weaker snow, smooth and rounded or lens shaped features.  They may sound hollow or crack out from your ski tip or snowmachine as you travel across them.  Shooting cracks and whumping are signs of instability and indicators of this avalanche problem.

Expect wind slabs to become less reactive within 24-48 hours after the storm ends.

Loose dry avalanches (sluffs) will be likely to trigger at all elevations, on all aspects, on slopes steeper than 40º. Expect the volume of sluff to be considerably larger at upper elevation and smaller at low elevation.

Expect sluffs to gain more momentum and run further above 4000′ where cooler temps during the storm combined with lower density snow has accumulated.  Any buried crust or smooth bed surface will contribute to the size and speed of this problem.

Avoid steep slopes above terrain traps. These avalanches will be capable of sweeping you off your feet and carrying you into terrain traps, compounding the hazard.

Lastly, pay attention to aspects with significant warming throughout the day from extensive cloud cover and greenhousing. As snow surfaces become more gloppy and stick to your skis and machine this is an indicator that the snow is losing strength and wet loose will be possible in steep terrain.