Comparing BC and Wash Avalanche Forecasts

[Dru]

Here's ours for the south coast:

 

South Coast Region

 

WEATHER: Although the weather is so bad that most observers can not record anything but avalanche deposits at valley bottom, one summed the weather events of the last few days up nicely. “This is the worst weather we have seen this winter”, read the report. The weather forecast predicts strong winds, further warming and up to 150 mm of additional precipitation for the latter part of the week.

SNOWPACK: Many areas had a weak wind slab before the storm began, which will be buried down as much as 100 cm by now. In areas slightly inland, a layer of faceted snow formed during the cold snap that preceeded this storm. This weakness, now

under as much as 100 cm of storm snow, has begun to fail. A surface hoar layer down about 150 cm may become active as well, so look for that in snow pits and test it’s strength if found.

AVALANCHES: Observers that did make it out for a look in the field today reported widespread natural activity in the alpine at treeline, with some slides running full path into valley bottom. Although it could not be determined which layer was failing, the storm snow and the faceted layer just below are suspected.

FORECAST OF AVALANCHE DANGER UP TO FRIDAY EVENING (March 14th)

ALPINE - Extreme

TREELINE - Extreme

BELOW TREELINE – High, areas of Extreme

TRAVEL ADVISORY: The weather forecast predicts this storm will continue to deliver moisture and raise freezing levels for the rest of the week. Avalanche danger is near the top of the scale and still increasing. The CAA, with financial assistance from the BC Provincial Emergency Program, has been publishing extra-ordinary bulletins this week to provide additional information during this fast paced and very dangerous period. Check www.avalanche.ca daily this week for possible updates to this bulletin.

 

 

 

How does it stack up against Washington's?? The S coast one is always pretty conservative since they are trying to give one forecast for everything from waddington, to whistler back country, joffre lakes, south chilcotins, to hope. wondering if Wash pases etc are predicted as more stable?

 

 

[JoshK]

SNOWPACK ANALYSIS.....

Periods of very strong winds and very heavy snow accumulations

were seen from about last Wednesday through last Sunday. Sites

near and west of the crest accumulated 4-7 feet of snowfall

during that time. Sites east of the crest accumulated less such

as Mission Ridge with about 1.5 feet. This caused a major

avalanche cycle near and west of the crest with many storm cycle

soft slab avalanche incidents but no fatalities. Generally

decreasing winds, much lighter precipitation and more stable

surface crusts Monday and Tuesday combined with substantial snow

pack settlement to reduce the avalanche danger. Total snow pack

settlement at sites near and west of the crest varies from about

1-2 feet the past few days. An exception was Mt Baker which

accumulated another 12 inches of snow on Tuesday. Heavy rain was

generally seen on Wednesday in the southwest Olympics and in the

Washington Cascades near and west of the crest from about Mt

Rainier north. Many sites near the Cascade crest had roughly 2-3

inches of water mostly as rain with Mt Baker picking up over 4

inches. The loading and weakening by the rain and warm

temperatures should have resulted in some large natural wet snow

avalanches in the backcountry in this area. We have only one

initial report so far Thursday morning of such an avalanche in a

back country area in White Pine Creek east of Stevens Pass. Sites

at Mt Hood had almost no precipitation Wednesday and another

several inches of snow pack settlement.

 

SOUTHWEST OLYMPICS...WASHINGTON CASCADES NEAR AND WEST OF THE

CREST MT RAINIER NORTH...

High avalanche danger above 4-5000 feet and considerable below

Thursday. Avalanche danger decreasing Friday becoming

considerable above 5000 feet and moderate below.

 

[JoshK]

Dru, it does seem to me that the B.C. forecasts are a bit more conservative. It looks like they tent to err on the side of caution and would rather bump to a higher level than a lower level. I guess this doesn't surprise me; I've actually been surprised sometimes that they avy report in WA wasn't higher when I've gone out and found scary conditions. Actually, my closest call with an avy to date was during a period where "low" conditions were forecasted. From what I could see around me, the snowpack actually held quite a bit of danger that wasn't mentioned in the forecast. I suppose this could have been due to local effects in the area that I was in, but you never know. I'm certainly no expert. I just take the avy forecasts as a general go/no-go helper for the entire trip and evaluate the conditions as I go along. I think I almost always err on the side of caution, mostly as a side effect of not knowing any better, and I figure being alive is better than not.

[Dru]

also, your backcountry is lower, warmer and wetter than much of our backcountry. hence more stable?

 

ive been trying to figure outr for much of the winter if the baker area forecast is more accurate than the south coast forecast for the chilliwack valley area. but baker forecast tends to track pretty closely to the Bc "below and at treeline" forecast hazard rating, the times i have checked it.

[gapertimmy]

all in know is that its in the 60's down here in Bend today, winter last week, spring this week

[mattp]

Dru-

Our forecast is specifically stated to be for areas below 7,000 feet, and this mostly means areas at or below treeline, so your correlation might be expected to at least some degree. I have, as Josh indicated, found scary slopes when the hazard was rated only "considerable" or something, but I don't think they under-rate the hazard in the Washington forecast if you look at how the hazard levels are defined. And certainly, I have been skiing up around Pemberton when I thought they may have slightly overrated the hazard - at least as far as the Duffy Lake road peaks were concerned, and this may be due to what you pointed out about how they have one rating for everywhere from Chilcotin to Serratus.

 

Meanwhile, how about this weather, huh? I don't have to check the avvy forecast to know that there must be some HUGE piles of avvy debris in the basin below the north side of Mount Shuksan right now and it would probably be a good area to avoid for the next couple of days.