Tricky times out there. We are expecting an upslope storm to arrive overnight and last for a day or two. Timing and amounts of snow are questionable, which also adds some uncertainty to the ratings. The underlying (pun intended) issue is the crust and how it will interact with the new snow. Watch this interface very carefully!
Ridge winds will pick up tomorrow AND shift directions. Watch for active windloading in the latter part of the day. This snow will be quivering on top of our new crust...which is everywhere.
This will still be an issue in areas that escaped the heat.
This layer is shielded by 2 crusts, but is still triggerable from thin to thick transitions. Very much a low probability, high consequence situation.
No new avalanche were observed,
Temperatures today were once again above zero, but not nearly what we've experienced for the past while. With that in mind, lets talk crusts. If the existing moist snow freezes completely, and it looks like it will, expect the crust surface to be hard, smooth and a poor bonding surface for the new snow. Ideally the snow will retain some heat as the snow starts, but this may not happen on all aspects. The glass-half-full situation is the crust remains slightly damp and bonds well with the new snow; and the glass-half-empty scenario is the crust will freeze solid, which will make for a potentially poor bonding surface. In reality, we'll probably see a little bit of both depending on aspect/elevation. As for the rest of the snowpack, Beneath the crust is, and will stay moist for some time. Down the road this could cause a couple of issues, but lets leave that discussion for a different day.
Winter...is that you? Tomorrow will see a dramatic change in our weather pattern. Cooling will start this afternoon, followed by snow starting around midnight. Before we talk incoming snow, I'll elaborate on the temperatures as they'll be important. We'll have a few hours of cooling before the snow starts. Overnight low of -3, and then a steady drop during the afternoon to settle at -8 by late evening. The longer the cooling period is before the snow, the firmer (and possibly slipperier) the impending crust will be. Snow amounts will be a modest 5-10cm by tomorrow night with winds circling to a NE flow tomorrow morning. There is an upslope component to this storm, snow amounts will likely vary from the predicted.
More details can be found in the Mountain Weather Forecast.
