NWAC Report

[B Deleted_Beck]

The NWAC report only covers up to 7,000'... why is that? Will the report for 7,000 typically be representative of conditions higher up? Are conditions higher up simply too unpredictable to accurately predict? Do climbers really pay much attention to the NWAC report, or do you trust only your own pit assessment?

 

Thanks

 

-Ben

[pcg]

First, I'm no avy expert. Second, I'm more a bc skier than a climber, but here's my thoughts on this...

Will the report for 7,000 typically be representative of conditions higher up?

No. If you look at the avy report it usually gets worse the higher you go in elevation, so I assume it is progressively worse above 7000'.

I'm not sure why there is no prediction for elevations above 7000'. One reason is that most bc skiers don't go that high.

 

Do climbers really pay much attention to the NWAC report, or do you trust only your own pit assessment?

I really don't trust anything. Seriously. Digging a pit provides useful information, bit it can never provide a green light, only a red light.

I am constantly feeling the snopack under my skis and listening and watching around me for any sign of danger, constantly proceeding under a yellow light and looking for red lights. Summer is different, but not this time of year.

 

While the NWAC report does not report specifically on conditions above 7000', it offers very useful commentary regarding what has been happening under the snow and this is what I pay most attention to. Then I try to extrapolate what avy conditions above 7000' might be based on the temps, recent snowfall, and wind above 7000'. In general the higher you go the consolidation process within the snowpack is happening slower in the winter because temps are colder. Also this means more faceting can be occurring within the snowpack. Also winds are higher above 7000' so that must be taken into account as well.

 

I am always alert for danger signs in weather patterns. For example, regarding this weekend on Hood, Saturday (afternoon especially) is a warming trend immediately after new snowfall - not good. How much snowfall remains to be seen, but the first warming period is generally not a good time to be on new fallen snow in avy terrain (Hood crater). The encouraging thing is that the snowfall so far seems to be rather light. However, lee slopes can still be loaded. In general, two things make me very wary - heavy snowfall and wind. Either by itself is reason to be concerned.

 

As everyone will tell you, there is no magic formula or bulletproof forecast to give you a green light, at least not for this time of year. If the avy forecast in general seems encouraging, then I might proceed and get out on the snow and continue to look for reasons not to proceed.

 

[Tyson.g]

I think pcgs' logic is sound, and well stated.

Good advice.

[AlpineK]

Forecast involved regular monitoring. Monitoring = $$ and areas above 7- grand are accessed infrequently. Calling a park ranger at Rainier might yield more information, but I'd expect things to be more unstable than the avy level predicted at 7.

[B Deleted_Beck]

For research sake, on a day like today...

 

The NWAC originally called for considerable above 5,000 on all aspects, and moderate below. The reason being was warming temps over recent storm slab and with sun.. so the danger was wet slab. They changed that to only considerable on S to SE aspects today, but that was the original call. Temps on the mountain were well above freezing below around 8,000'.

 

For this next week, based on everything I've learned so far this winter, I'm guessing we're gonna be looking at a very similar avy report through at least friday- very warm temps creating wet snow and in sun, leading to considerable avy hazard on all aspects, and especially on sun exposed slopes.

 

Since the report only goes to 7,000, for conditions like this, wouldn't the wet-slab danger decrease with elevation? It's going to be colder and colder for longer higher up. Shouldn't that create generally more stable conditions on the higher/steeper slopes, at least until the sun comes out and bakes the shit out of everything during the day?

Edited March 5, 2012 by Ben B.

[Mtguide]

Gain in elevation also translates to heavier snowfall. While higher winds at increased el. can reduce to some extent any consistent depth of snowpack, in so doing they can also cause more windloading on lee slopes, deeper drifts, larger, more unstable cornices, and lensed and cross-bedded layers. All that snow has to be redistributed somewhere. These conditions can make it very difficult to tell what's going on just by digging simple test pits. These are all complex and dangerous features which can increase the difficulty and hazard for safe routefinding. Windpack on windward slopes can cause hard crust which can set up dangerous conditions when poorly bonded with subsequent snowfall. And as PCG explained very well in his post above, colder conditions at higher el. can actually cause less consolidation and poor bonding between layers. All these factors combined can set up a real minefield.

 

Furthermore, temps at upper elevations can be very tricky. Although generally you'd think it would get colder as you go higher, the opposite can also be true, depending on the time of day, and at times when lower elevations are cloud-covered and upper slopes are in the clear. South-facing slopes can be like a bake oven in clear weather, especially in calm conditions, and poorly bonded layers in the snowpack can approach a hair-trigger balance of adhesion as the sun-softened surface meltwater percolates down through the snowpack. Elevation is no guarantee of stability or safety.

 

So, as a general rule, if avy conditions are unsafe from 5000 to 7000 el. they're only going to be more so the higher you go. Even if the upper snowpack were to be more stable, you'd still have to travel through the danger zone below 7000 both to get to it, and on the return back down. Thus you have a double exposure over the course of the day, and on the descent you're entering the danger zone at the worst time of day, as/after warming has further destabilized the already unsafe slopes. Additional conditions such as continuing snowfall, high wind, or warmer afternoon updrafts may only increase the risk. Not exactly a recipe for a safe trip. And, should there be an incident, you're putting your companions, and rescuers into a shooting gallery, not the most ethical or responsible choice.

Edited March 5, 2012 by Mtguide