Finally a change to the weather. After a very dry January (17 cm total at Bow Summit), the pattern has shifted and we expect 10-20 cm of new snow and strong winds through Saturday. Avalanche danger will rise quickly as the bond between new and old snow will be poor. Ice climbers: small avalanches may run further than expected in gullies.
Dry loose avalanches are certain to occur in steep areas, cliffs and gullies as the new snow is coming in cold, will not bond to the old surface and will sluff easily. Ice climbers should zip up their hoods and be wary of sluff inside gullied climbing routes.
New snow combined with wind will create fresh slabs that will release easily as both natural and human triggered. These may be small (depending on snow amounts), but they should release easily because the bond to the Jan 30 surface will be poor.
The snowpack this season is very shallow, with weak facets and depth hoar on or near the ground. This kind of snowpack will not support much additional load, and we expect these kinds of ground avalanches may reawaken if enough snow falls during this storm.
No new slab avalanches were observed or reported on Thursday, but the storm was starting and visibility was limited. Our field team reported a lot of loose dry snow (spindrift) blowing around in the cliff and numerous dry loose sluffs starting to run.
5-20 cm of new snow and strong winds will create surface slabs that bond poorly to the underlying snow. The layer being buried on Jan 30 is a mix of crust, surface hoar and facets - none of which will bond well to the new snow. We expect avalanches to begin failing early in the storm with minimal accumulation. The snowpack is generally weak, with an old crust and depth hoar at the base, so any avalanches starting in the surface layers may step down to the ground and become larger.
The weather pattern has changed significantly (finally), and there's now a strong onshore flow of moist Pacific air colliding with cold Arctic air. This combination will produce snow. We expect 5-10 cm through the day on Friday, possibly up to 15 cm. Temperatures will be steady around -12 and winds will be strong from the northwest. The storm ends on Saturday and -25 arrives on Sunday night.
