I did an observation flight for a number of the industrial projects I am working on to see what came of this last storm:
In my opinion the CAA
nailed the hazard forecast at Alp: Considerable, TL: Moderate, BTL: Moderate. I didn’t make it
to the North Shore Mountains so can't comment there, but I would be a little extra cautious at
treeline in southern Garibaldi Park, Tricouni, Ashlu Divide and Tantalus area. With
the forecast warming and possible inversion be aware of the temperatures and
conditions above you.
Three distinct snow zones were observed on the flight. They are illustrated in the attached map and described in more detail below.
1 Clowhom, Squamish, Ashlu Divide, Southern Garibaldi Park.
This zone received between
65-90cm of snow with the last storm with a freezing level over 850m and
possibly as high as 1300m during periods of the storm.
Toward the end of the storm
several large avalanches released. Their flanks and crowns are still incredibly
sharp and range from 60-120cm deep. There was wide spread propagation (up to 1000m) and the
slides travelled far and fast reaching valley bottom. The majority of the
slides were large size2 but there were half a dozen slides of size 3.5 or
greater. It appeared that all the slides released on the Jan 23 layer and
nothing came out any deeper. The avalanches were observed on all aspects.
Also of note is that there were
several wet slides below treeline, which was clearly a product of the high
freezing levels at the start of the last storm.
Going forward my concern for this
zone is that not all the slopes slid. Most slides started at ridge top and at
times propagated into terrain as low angle as 25 degrees, but only about 75% of
what I would consider obvious avalanche terrain had slid.
2. Calaghan, Rutherford, Miller, Northern Garibaldi, Joffre, Stein,
Nahatlach, Harrsion Lake.
This area saw significantly less
snow than the south with total storm snow amounts ranging from 20-50cm. It
appeared that there was just not enough snow to start the Dec 23 layer going…or
maybe it had already slid.
In the Mt Cailey and Fee area there
were dozens of snowmobilers poking into some pretty steep terrain, but they
were staying away from the regular performers and cross loaded features and had
not started a single slide that I could see.
Throughout the zone there were a handful of small
(sz 1-2.5) slides that had come down
during this last storm. They didn’t run as far they did farther to the south. Also
interesting is that all the avalanches in this zone started low in the start
zones. It appears that the weakness had already come out at ridge top in most
areas.
I would take a little extra care in the southern and western parts of this area where there may have been more snow and wind during the last storm.
3. Golden Ears, Stave, Misty, Pit area.
This area got the most snow of
the entire flight with an estimate of 80-130cm of snow during the last storm at
the top of treeline. It appears generally that there is more snow to the SE of
the Coast Mountains than anywhere else.
Several avalanches occurred mid
storm in this zone and some of them were quite deep (200cm, Jan04?). Most of
the slides were covered with 20-50cm of snow. There were a few small avalanches
toward the end of the storm that came out at ridge top within the storm snow,
but no recent deep avalanches.
Surprised you made it this far....I had a hard time reading it all myself.
Conny Amelunxen
MG
