It doesn’t get much better than that. Fresh snow + wind coming. Heed snowdrifts in northern regions.

Favorable avalanche situation all last week

Last week was favored by a positive avalanche situation, generally lower avalanche danger levels and correspondingly fewer avalanche prone locations. This was primarily due to the very stable high-pressure weather front. The atmosphere was unusually dry, temperatures somewhat lower than the previous week, nighttime skies clear and star-studded. Thus, the snowpack which had superficially softened on sunny slopes during the daytime was able to consolidate. From day to day, the melt-freeze crust which formed became thicker, more capable of bearing loads. The main problem during the mornings shifted to the risks of falling on the steep, hardened frozen surfaces, rather than avalanches. Even in the afternoons the snowpack did not really soften down deep, which is one of the reasons why only one single avalanche was reported last week: a glide-snow avalanche in the Northern Alps.

A star-studded night in the Glockner region

A (nearly) flawless week lies behind us. Only a weak cold front brushed North Tirol on Saturday, 27 February. Thereafter, the unusually dry air masses are visible. Perfect nocturnal outgoing radiation.

The green points show precipitation on 27.02.2021. This was in the north, mostly just a few millimetres.

“Firn snow” - more correctly corn snow for gourmets. That is how the last week unfolded for winter sports enthusiasts. Ausserfern (photo: 02.03.2021)

Not an everyday occurrence: such a massive melt-freeze crust, though only at low altitudes

Also here, just before 1:00 pm in very steep south-facing terrain at 2450m: superficially softened snow, beneath that a massive melt-freeze crust atop a loosely-packed moist fundament 

Glide-snow avalanches have become quite rare

Following a - for this juncture of the season - striking avalanche cycle til 25.02.2021 in which there were a great many glide-snow avalanches, last week there were practically none. That fits in with our long-term observations: to have such a weather period following a spell of heightened naturally triggered avalanche activity.

 

Marked in red: glide crack in Northern Massif (02.03.2021)

A little while later: a glide-snow avalanche on the same spot (photo: 02.03.2021)

The ground is becoming bare on sunny slopes due to daytime warmth and solar radiation, as well as from already discharged avalanches. Navistal, western Tux Alps (photo: 27.02.2021)

A cold front will bring some snow and wind from the north to North Tirol on Friday, 5 March

In the northern regions, a cold front is scheduled to arrive tomorrow, 5 March. In the furthermost north, it is expected to bring 10-20 cm, locally as much as 30 cm of fresh snow. The snowfall will be accompanied by winds stronger than transport velocity from northerly directions. The amounts of fresh snow will decrease towards the south.

North Tirol and northernmost East Tirol will get the brunt of the snow.

Obviously, fresh snow makes us ask: what will it be deposited on?

• On sunny slopes, mostly atop a hard melt-freeze crust. Only loosely-packed blanketed-over fresh snow could form a weak layer for small slab avalanches there.
  
  
• On shady slopes in wind-protected terrain above 2000 m there is currently a weak layer of faceted (expansively metamorphosed) crystals which has formed beneath a thin crust. Where the snow is shallow, this layer is more marked. One also finds small-spread nests of depth hoar there. So on shady slopes there is regional potential for weak layers lurking below freshly generated snowdrift accumulations. The danger zones will be relatively small and, for experienced backcountry tourers, easily recognized.

Skies are already turning gray in North Tirol, as here on the Arlberg.

Beneath a thin wind crust, faceted crystals have formed. However, only large additional loading could unleash this layer.

Visible in this snow profile from the Silvretta are the faceted crystals on the snowpack surface. North, 2330m. Fresh snowdrifts would bond poorly here. 

On the weekend, loose-snow avalanches in the north


Fresh snow in spring reacts very swiftly to impulses coming from warmth and solar radiation. For that reason, special caution is required starting on Saturday, 6 March, when the sun comes out again, towards naturally triggered loose-snow slides in extremely steep terrain.


In southern regions, still hardly any avalanche prone locations


In the southern regions (as well as in the north, apart from freshly generated snowdrifts) favourable conditions continue to reign.

In many parts of East Tirol, there are above average amounts of (compact) snow for this juncture of the season. (photo: 28.02.2021)

In isolated cases, glide-snow avalanches are still possible: areas below glide cracks should ongoingly be circumvented. The danger of taking a fall continues to threaten, due to the hard surfaces. This includes zones with snowfall, since only a few centimetres of fresh snow is deposited on top of a hard-as-iron surface.

To wrap up, we want to add a further tip for winter sports enthusiasts to supplement our information in the last blog...for those who were lucky enough not to be struck by falling rocks pried loose by grazing chamoix.

Chamoix in extremely steep terrain. Grazing...and loosening rocks. Northern Massif  (02.03.2021)