Avalanche Advisory for Saturday, November 18, 2017 at 7:00 am

Issued: Sat, Nov 18, 2017 at 8AM

Expires: Sun, Nov 19, 2017

Welcome to the beginning of the 2017/2018 HPAC avalanche advisory season! A huge thank you to our community who makes this possible.

Thank you to the many people who have already submitted observations this season, which have been a huge benefit to our community. If you are out and about HP, please share your pictures, video and observations here. Go to Facebook and follow us now.

Thank you to the people who have already donated dollars this season! This is a reminder that we can only make HPAC possible with individual donations from you!

 

Above 3,500ft Moderate

2,500 to 3,500ft Low

Below 2,500ft Low

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

BOTTOM LINE:

A moderate avalanche hazard exists for small, persistent slabs in specific locations at upper elevations. The avalanche hazard is low for loose dry avalanches, which are low volume, slow in running speed. Neither type of avalanche problem are expected to be able to bury, injure or kill, however, each could sweep you into other terrain traps, compounding the hazard.

At least a few old, sluggish weak layers in the mid to deep snowpack are stable today. Watch these layers carefully over time, as new loads could re-activate them.


PERSISTENT SLAB AVALANCHE PROBLEM: Winds earlier in the week briefly spiked transporting low density snow and forming shallow, 4-6″ soft wind slabs. These old wind slabs, now persistent slabs, are in specific areas on leeward aspects, mostly West to North, at upper elevations. You may also find these slabs on the leeward aspects, generally West to North, of gaps and passes at mid elevations. Persistent slabs are sitting on weak, faceted snow. Natural avalanches are unlikely, but human triggered are possible. In most cases these slabs will be stubborn to trigger, however, on slopes steeper than 45º and/or where the snowpack is thinner and rockier, they will be easier to trigger. Expect these slabs to be small, incapable of burying or injuring a person, but able to sweep you into, or over, more consequential terrain traps compounding the hazard; D1 or less in size.

DRY LOOSE AVALANCHE PROBLEM: “Sluffing“, or Dry Loose avalanches, will be low volume and slow running. Natural activity is not expected, but human triggers will be possible, on all aspects, at mid to upper elevations, especially on slopes 45º and steeper.  Again, the volume and speed are very low, not capable of burying a person; mostly less than D1 in size. However, as with any sluff, it may be possible to sweep you into, or over, more consequential terrain traps.


Recent, relevant snow pit profile here


More information here on specific avalanche problems.

Recent Avalanche Activity

One wind slab, human triggered, likely occurring yesterday, was observed on a steep slope at ridgeline in the Rae Wallace Chutes. The slope is over 45º, generally skirted across to access other terrain. This portion of terrain is generally shallow and rocky, producing weak facets, the likely culprit in this event. Size was approximately 4-6″ deep, 15 feet wide, 20 feet long. This could have swept the person through shallow rocky terrain, compounding the hazard. No witness reports yet and no known capture or injury.

 

Recent Weather

1-6″ of snow accumulated between 2500′ and 5000′ during Thursday’s brief storm. This snow sits on a variety of crust, snow surfaces, and near surface facets.

At 4500′ winds averaged 4 mph, max gust of 25 mph from SSE. Temperatures averaged 17ºF with a max of 30ºF and a min of  8.7ºF and dropping this morning.


When you check the weather forecast, make sure to check out the NWS RECREATIONAL FORECAST for Hatcher Pass.  NWS puts extra time and resources into this forecast specific to the mountains at Hatcher Pass, Turnagain Arm and Thompson Pass.


NWS point forecast here


State Parks snow report here


Yesterday’s weather:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Additional Info & Media

Reminder:

The TERRAIN is the same as it was yesterday. The SNOW may not be. Experts use this gift everyday to their advantage and so can you. If there is ever a question about stability, use terrain defensively.

If you are traveling in avalanche terrain, S P R E A D  O U T!  Stay tight and socialize before you get into the meat of it. Then space out and use safe zones to move through avalanche terrain, strategically, one at a time. Or, on a big open slope, simply increase your spacing, to the point that you would have to yell to communicate. We have seen some good stability lately, and observed many folks being complacent, walking nose to tail in avalanche terrain, above terrain traps. This is an unnecessary risk which builds poor habits. Habits tend to loosen over time; tighten it up!

And one more piece of good advice from Doug Krause, avalanche Guru. You can check out his very hearty avalanche and communication rant on Slide; The Avalanche Podcast. iTunes and Soundcloud

Extracted from S2E1: The avalanche forecast is your starting point, then you need to do something with it.


The Avalanche Hazard will remain the same through today and likely through the weekend and into early next week. Snow is in the forecast for this evening and into Sunday, although it appears to be another brief storm with limited accumulation.

 

Watch the weather and look for any rapid warming or significant load which could activate mid, to deep pack, weak layers. This could increase the avalanche hazard.

 

Posted in HPAC Forecasts.
Jed Workman

Forecaster: Jed Workman