This is not an Avalanche Advisory. This information is a Conditions Update. The next avalanche advisory is scheduled for Saturday December 29, 2018.
MIDWEEK SNOW AND AVALANCHE CONDITIONS SUMMARY
Avalanche conditions in Hatcher Pass are improving. Human triggered avalanches 1-4 ft deep are still possible in steep isolated locations at mid to upper elevations, mostly on upper elevation leeward (West through North) terrain. Practice good travel protocol by skiing and riding one at a time, spotting your partner, and watching your partners away from the runout. Practice terrain progression by starting with smaller, low consequence terrain. Avoid terrain traps where even a small slide could have big consequences.
This report is a mid-week conditions update, so please be sure to check hpavalanche.org for advisories on Saturdays and follow the HPAC Facebook for updates. Help us keep tabs on the Hatcher Pass area! If you see any avalanche activity send us an observation HERE. Thank you to everyone who has already submitted observations this season - you can see those HERE!
Problem 1: Old Wind Slab
Winds on Sunday were strong enough from the East to transport soft snow and build wind slabs on West through North terrain. Upper elevations have received the majority of the winds and are starting to have more variable surface conditions along ridge lines. These zones contain a variety of breakable and supportable wind crusts, packed powder, sastrugi, and bare ground. On leeward, generally west through north aspects, pockets of 4-10” thick old wind slabs were found sitting on weaker snow underneath by observers on Sunday through Tuesday. Wind slabs will vary in size from small to large, be stubborn to trigger, and will be more likely to trigger in terrain steeper than 35°. Even a small wind slab can have high consequences when the terrain funnels into a terrain trap.
Pay attention to how the snow feels and sounds under you. Stiff snow that is hollow and drumlike is usually a wind slab. Pole probing is a good way to figure out if you are on a wind slab that is overlying weaker layers. Hard, supportable wind slabs can allow you to travel out onto them before breaking above you.
Human triggered wind slab on Marmot on Sunday. The slab is up to 1' thick in places.
Problem 2: Persistent Slab
The weather has continued to be dominated by mild conditions since the last major storm cycle of December 8th. This is allowing the snowpack to heal and bond. The last human triggered persistent slab avalanche was on December 9th, and the last reported natural avalanche was on December 18th. People have been able to get out and explore steeper terrain without consequence.
While the likelihood of triggering an avalanche has decreased, widespread poor structure still exists. It is still possible to trigger an avalanche large enough to bury, injure, or kill a person (D2), especially in isolated locations at upper elevations in previously wind-loaded terrain steeper than 35°. Observers on Sunday through Tuesday found various layers of weak, faceted snow sitting under a stiff slab 1-2’ thick above 2500’ on NW aspects. These weak layers were stubborn to reactive in stability tests, but don't expect stability tests to be reliable or consistent with this kind of avalanche problem. You may not experience obvious signs of avalanche danger such as whumphing, shooting cracks, or collapsing before you trigger an avalanche.
The key to managing this avalanche problem is to hedge your bets by carefully selecting terrain. Avoid terrain traps like you avoid your aunt’s week old fruit cake! This is easier said than done: Hatcher Pass is littered with terrain traps such as gullies, ravines, cliffs, and abrupt changes from steep to flat that could amplify the consequences of even a small slide.
You can decrease the consequences of an avalanche by choosing slopes with gentle, fanning runouts and expose only one person at a time to the possible hazard.
Various weak layers of snow sit below a 1-4' thick slab above 2500', especially in previously wind loaded areas.
Hatcher Pass has no shortage of terrain traps, as seen here on Marmot, where steep slopes hang above gullies, ravines, and creeks that could greatly amplify the consequences of even a small slide.
Some terrain traps are less obvious. Large, connected faces that end abruptly in flat areas or benches can allow avalanche debris to pile deeply, as it did here on the NE face of Hatch Peak in a December 9th avalanche that buried two people.
Human triggered wind slab reported on Sunday 12/23. You can see the observation here.
No other avalanche activity has been report at this time.
Winds picked up slightly this week, with Easterly winds at ridge tops gusting to moderate Sunday 12/23. At Independence Mine, winds have been calm to light from the North since Saturday 12/22. Independence Mine has received no measurable precipitation since Saturday 12/22. Temperatures have been mild with a high of 33° F on Sunday 12/23, high of 21° F on Monday, and a high of 27° F on Tuesday and Wednesday. Lows have hovered around 20° F.
Thursday 12/27 through Saturday 12/29, the weather is expected to be overcast with temperatures in the upper 20's F during the day, with calm to light winds from the east and southeast. The best chance for snow is Thursday through early Friday morning, with 1-3" accumulation.
Stay tuned to the NOAA point forecast for an updated weather forecast each day. The best way to see if it's snowing in Hatcher Pass is to look at the webcam snow stake HERE and the Independence Mine SNOTEL site HERE
Avalanche conditions in Hatcher Pass are improving. Human triggered avalanches 1-4 ft deep are still possible in steep isolated locations at mid to upper elevations, mostly on leeward (West through North) terrain. Practice good travel protocol by skiing and riding one at a time, spotting your partner, and watching your partners away from the runout. Practice terrain progression by starting with smaller, low consequence terrain. Avoid terrain traps where even a small slide could have big consequences.
Mark your calendars for the annual Hatcher Pass Avalanche Workshop coming up on Saturday January 19th.
Save the Date:
HPAC Annual Fundraiser and Cabin Fever Reliever, Saturday,February 9th, 2019 at the Moose Lodge in Palmer.
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