Last week avalanche dangers began to increase due to a thoroughly wet snowpack. A marked drop in temperatures and dry air masses led to a very favorable avalanche situation with low danger. Now the overall weather front is changing again: it’s getting warmer and successively wetter. Wet-snow problems are again coming to the forefront.
Review of last week
Let’s have a look at one of our numerous weather station graphs, the one from Kitzbüheler Horn:
On Sunday, 06.04, we were confronted with an interesting phenomenon for a short time: the melt-freeze crust that had formed at night was capable of bearing loads yet was triggered as a slab by winter sports enthusiasts in a narrow altitude band on sunny slopes. The culprit: the loose old snowpack surface which had just become thoroughly wet was the weak layer.
Over the next few days an increasingly thick melt-freeze crust formed on sunny slopes. The snowpack was stable far and wide. Avalanche danger was low. Snow quality varied, as is typical of this juncture of the season, from good powder, top quality firn to breakable crusts.
Typical profile for shady slopes. Active weak layers from early April (graupel on 29.03 and faceted crystals that formed on 10.03) could no longer be disturbed at this location. On shady high-altitude slopes, still temperature reserves inside the snow.The currently still thick melt-freeze crust atop a loosely-packed, moist-to-wet old snowpack will now become steadily thinner, the snowpack will become more prone to triggering.
Brief outlook
The weather is about to change. The next few days will be measurably warmer, the air starting on Sunday at latest will become more moist. Thus, we can expect the wet-snow problems to increase day by day. Since in spring even little changes have big impact on snowpack stability, and thus, also on avalanche danger, we want to call your attention to the current Avalanche Bulletin which is published every day at 5:00 pm.
