In a nutshell...
Till now the Easter holidays have been much too cool for this juncture of the season (Easter has been colder than Christmas). On the other hand, that meant that the snow which fell this week was able to remain good powder for a long time. The near-surface weak layer problem generated by dp.4 (cold on warm) currently seems most threatening above 2600m. Danger zones are rare. It occurs mostly extremely steep N/NE/E facing slopes.
Mostly favorable avalanche situation
Reports from winter sports enthusiasts, snowpack analysis and information about avalanches which have released reveal a mostly favorable avalanche situation.
.jpg "Die vergangene Woche stand vielerorts im Zeichen guten Pulverschnees. Karnische Alpen (Foto: 06.04.2023)") |
| Last week had lots of great powder. Carnic Alps (photo: 06.04.2023) |
.jpg "Ähnliches Bild mit gutem Pulverschnee in den Sellrainer Bergen (Foto: 06.04.2023)") |
| Another snapshot of terrific powder in the Sellrain mountains. (photo: 06.04.2023) |
Near-surface weak layers found increasingly on N/NE/E facing slopes at 2700-3100m
We were able to observe the danger pattern described in our last blog (cold on warm) in many places, but stability tests mostly showed only partial fractures in the weak layer. That fits with the fact that most of the dp.4-relevant avalanches last week occurred in extremely steep terrain. What was striking, was how many of them were on N/NE/E facing slopes at 2700m-3100m (Wasserkar-Weikugelgruppe / Müncher Abfahrt-Weißkugelgruppe / Zirmkogel-Gurgler Gruppe / Wildgratscharte-Alpeiner Berge / Stöcklengrube-Alpeiner Berge / Federbettkees-Zentrale Zillertaler Alpen / Kleiner Happ-Venedigergruppe / Wagenstein-Östliche Deferegger Alpen).
.jpg "Typisches Bild eines Schneeprofils: Zuoberst: Schneeauflage ab 25.03. Die glatte Fläche darunter zeigt eine unvollständige Bruchfläche einer dünnen kantigen Schicht auf einem (in diesem Fall gut ausgeprägten) Schmelzharschdeckel. Darunter erkennt man gefrorene Wasserkanäle vom Warmwetter vor dem 25.03.2023") |
| Typical snow profile: at top, snowfall from 25.03. The smooth surface beneath that shows the partial fracture of a thin faceted layer atop a pronounced melt-freeze crust. Beneath that, a frozen water canal from the warm-weather period before 25.03 is visible. |
Minor snowdrift problem
The snowfall from the beginning of this week occurred at low temperatures and was transported at high altitudes. When snowdrifts are deposited on cold, loose fresh snow (even snow-fluff was observed) there is a heightened likelihood of slab avalanches triggering. With sufficient experience, such danger zones are easily recognized and can be circumvented. The danger zones currently (07.04.2023) occur especially on very steep ridgeline shady slopes.
.jpg "Kammnaher Triebschnee in den Allgäuer Alpen (Foto: 04.04.2023)") |
| Snowdrift accumulations adjacent to a ridgeline in the Allgau Alps (photo: 04.04.2023) |
Caution: cornices
Cornices have become quite pronounced this spring. Keep an eye on the risks of taking a fall. In addition, additional loading caused by a breaking cornice can trigger an avalanche.
.jpg "Wechten im Gratbereich als mögliche alpine Gefahr (Foto: 06.04.2023)") |
| Cornices near the ridgeline: a potential alpine danger (photo: 06.04.2023) |
.jpg "Lawinenabgang aufgrund eines Wechtenbruchs beim Gufelseejoch (Foto: 04.04.2023)") |
| Avalanche due to a cornice breaking on Gufelseejoch (photo: 04.04.2023) |
Coupled to alpine dangers are the glaciers: increased risk of falling into crevices due to lack of snow.
Short review of this last week
A quick glimpse at the weather is easiest through an automated weather station.
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| At month’s end it was still warm, the snowpack surface was moist. Then some snowfall, initially accompanied by wind. Thereafter, temperatures dropped. Conditions improved rapidly. |
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| Fresh snowfall at the beginning of the week (02.04-03.04), most of which fell in eastern North Tirol and in northern East Tirol. |
.jpg "Eine großteils kalte Woche... Eis an einem Pistenfahrzeug am Stubaier Gletscher. (Foto: 04.04.2023)") |
| A cold week by and large...ice hanging from a piste vehicle on Stubai Glacier. (photo: 04.04.2023) |
.jpg "Immer wieder zu beobachten: Knapp unterhalb der Schneeoberfläche bildete sich aufgrund der kalten Temperaturen, des sehr lockeren Pulverschnees, der trockenen Luft und der intensiven Sonneneinstrahlung eine dünne feuchte Schicht, die anschließend zu einem dünnen Harschdeckel gefrierte. (Radiation recrystallisation nennt man diesen Prozess, der zu einer möglichen Schwachschicht für kommende Schneefälle führen kann. Schaut aktuell aber aufgrund der Wetterprognosen nicht nach einem auf uns zukommenden Problem aus.") |
| Often observable: just beneath the snowpack surface, a thin moist layer develops due to low temperatures, very loose powder, dry air and intensive solar radiation. This layer then freezes into a thin melt-freeze crust (radiation recrystallisation is the name of the process which leads to a weak layer forming for the next snowfall). At the moment, based on current weather forecasts, this does not seem to be a threat. |
What’s next?
April weather variability will continue, with some snowfall over the Easter holidays. No significant change is expected in the avalanche situation.
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| 48-hr fresh snow forecast from today, Good Friday, 07.04.2023 |
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| Until Easter Monday, repeated bouts of precipitation. Only light winds. Cold. |
HAPPY EASTER!
We wish you Happy Easter and a period which is both high in enjoyments and low in accidents out in backcountry terrain. Yours truly, the team of the Avalanche Warning Service Tirol.
