Avalanche Report for Southern Cairngorms
Avalanche Hazard Forecast
FOR PERIOD 18:00 Wed 04/03/2015 TO 18:00 Thu 05/03/2015
Forcasted Snow Stability & Avalanche Hazard
Stability will become increasingly poor throughout the day with unstable accumulations found on North through East to South-East aspects above 800 metres, especially in the deeper more extensive poor to weakly bonded accumulations. Cornices on Easterly aspects will be prone to collapse. The avalanche hazard will be Considerable.
Forcasted Weather Influences
The freezing level will rise above the summits with some very light rain later in the day. Gale force winds will increase during the day and mainly be from the South-West.
Key Snow Stability Observations
Observed Avalanche Hazard -
Observed Weather Influences
A dry and bright day with strong winds from the West.
Observed Snow Stability and Avalanche Hazard
There has been some consolidation of recent accumulations but deeper unstable windslab is still present mainly on North-East and Easterly aspects above 850 metres with localised areas also on Easterly aspects. Scoured areas and aspects are icy and stable. There was some loss of superficial snow at lower levels. Newly formed cornices were noted in places. The avalanche hazard is Considerable.
Firm snow - ice on most aspects. Cold clear conditions. Winds 30 -40 mph, progress difficult and tiring, easing slightly later.
Cornice collapse likely to be a trigger in thaw conditions. Good route selection will be essential for those out on the hill on Thursday.
We started this period post thaw with many areas becoming patchy and a firm and well bonded snowpack. Significant snowfall arrived on the 22nd and 23rd with new unstable accumulations developing on N to SE aspects and plenty of lying snow for the changeable winds to redistribute. Visiting Lochnagar post storm there were 2 sets of crown walls but not really any other debris. We finish this period with an overnight thaw on the 25th and cooler temperatures refreezing the snowpack.
There has been limited new snowfall this week with a general depletion of snow cover at lower elevations occurring throughout the period. Thaw conditions became established at all elevations overnight Tuesday into Wednesday which resulted in significant snow loss, especially in exposed locations. The end of the period has brought a rapid return to cooler conditions with the remaining snowpack becoming firm and well bonded.
The last week has been dominated by cold nights with dry and sunny days. Generally the snowpack has been consolidating slowly, despite the occasional appearance of surface hoar and in shaded areas at higher altitudes, facets. The temperatures within the snow have been getting warmer particularly on the Southerly aspects. In many locations the snow is very icy and we are forecast heavy snowfall, however some of this will end up on aspects that currently have little snow.
A stormy start to the week with heavy snow and very strong winds resulted in both wind scoured slopes and heavily drifted areas. Cold temperatures and subsequent drifting maintained a slow rate of consolidation with instability persisting. The end of the week has seen lighter winds and a gradually rise in the freezing level leading to a consolidating snowpack. At present snow is encountered from valley level, with heather, ice, neve and deep drifts all present.
Initially, windslab was mostly stabilised by a couple of brief thaws around the weekend, which were not too severe, although there was loss of superficial snow. Monday onwards has seen a series of snow showers, high amounts of drifting and much cooler temperatures with weak layers developing in new accumulations. Snow-ice exposed to the wind is very firm with exposed aspects and ridges scoured and icy.
Storms eased at the start of the week leaving a good cover of cold, dry snow which had fallen on strong variable winds. In many open locations the snow was very hard packed and started to consolidate, with instabilities restricted to steep terrain. There was a reasonably strong temperature gradient within the snowpack for much of the week, with a hint of facets starting to develop. We ended this period with a much cloudier and slightly milder day.
The start of the week brought new snow showers and fluctuating temperatures. There has been more significant new snow in the last 48 hours with a massive improvement in cover, with accumulations becoming deeper from valley level. Milder temperatures overnight helped consolidate deposits at lower levels but we finish the week with deep, unstable snow at higher elevations.
This week has been dominated by a couple of severe thaws which left the snow cover restricted to mainly NE to SE aspects above 900 metres. Any new snowfall was not really significant and was generally short lived in the fluctuating temperatures. Another cooler period on the overnight of the 7th has left older snow very hard and icy with some heavier snowfall and drifting leading to deeper accumulations forming in wind sheltered locations on North to East aspects above 800 metres.
Very cold conditions at the start of the period maintained a slow consolidation rate for the recently formed but localised windslab. Elsewhere the snow cover tended to be superficial. Towards the end of the period, with slightly warmer temperatures, the localised areas of windslab had stabilised. Significantly warmer temperatures and rain on 01/01/15 has depleted snow amounts to very patchy cover at all elevations. Note: Colder temperatures and snow showers forecast for 02/01/15.
After an unsettled period of stormy weather there was a significant thaw last weekend which depleted the snow cover considerably. Snow showers on Wednesday settling above 500 metres have improved the cover slightly with some drifting.
In early December strong winds, mostly from the West, accompanied by snow showers led to unstable windslab developing in some locations. The recent mild temperatures have helped consolidate the snowpack but with some snow loss particularly at lower levels. A couple of minor avalanches were reported, one apparently triggered by a ski-tourer.
The snow has continued to slowly thaw but has remained well bonded throughout the week. Snow cover is patchy, more extensive areas above 850 metres with burn lines and gullies holding most. Glide cracks continue to develop, particularly round corrie rims where there is still deep snow.
With the freezing levels above the summits and no significant precipitation the snowpack has been slowly thawing and consolidating for the last week. Snow cover is still reasonable above 750 metres but the ground is starting to break through in some locations. Many cornices have gone but steep poor quality snow often bars the exits of gullies.
Snowfall and drifting led to new unstable accumulations forming earlier in the week but overall stability was improved by fluctuating temperatures. Most of the snowpack has become moist but well bonded with some areas of moderately bonded snow mostly but not exclusively restricted to NW to E facing corries. More cornices have collapsed but there are still many left.
The snowpack has continued to thaw with significant snow loss, particularly under 800 metres. Although soft, cover has remained well bonded for most of this period. Glide cracks have been growing in some locations with cornice collapse, rock and ice fall also observed. There is a return to wintery conditions with snowfall today and a drop in the freezing level.
We started this period with some avalanche activity and collapsing cornices but the last few days have seen a settled period both from the weather and the snow. Currently the snowpack surface layers have refrozen but there are much softer layers deeper within the snow. There are also plenty of old cornices that can fall and act as a trigger.
As well as a reasonable amount of new snow, we've had a few thaw freeze cycles resulting in a quite a few avalanches throughout the area. Weaker layers have developed deeper within the snowpack and were exposed where triggered by cornice collapse. Otherwise stability continues to improve.
The most significant event this week was Sunday's thaw. There was a lot of rain which helped trigger multiple avalanches throughout the area. Since then stability has generally improved, as there has has not been too much new snow but there has been reasonable amounts of drifting every day. New pockets of windslab have developed on NW,N,NE and E aspects at higher altitudes and in some places are poorly bonded. Cornices continue to re-develop.
It was a slightly calmer week which was mostly cloudy. There was less snowfall than on previous days and we had rain on a couple of occasions. A number of crown walls or avalanche debris have been reported with the likely trigger being cornices, some of which are very big. Currently after last nights thaw snow cover is mostly wet and soft but had already started to re-freeze this afternoon above 800 metres. Cover remains good on most aspects from 600 m, deepest on W through N to E.
We have had significantly more snow but less so in the latter half of the week. Stability is slowly improving but the winds have been variable, leaving localised windslab in many sheltered locations from 600 metres and deeper areas on NW,N and NE aspects above 800 metres.
Very strong S/SE winds and snowfall, heavy at times has resulted in substantial accumulations above 750 metres, mostly on W through N to E aspects. Extensive areas of moderately bonded windslab was to be found in sheltered locations. There have been a number of avalanches, but due to the high winds and poor visibility it has been not practical to visit and record details yet. Recent quick thaws to summit level have helped stability with some snow loss at lower altitudes.
We have continued to have significant snowfall at times as well as brief thaws to summit level. In the latter half of the week we had a slight change with snowfall from the East. The winds have moved much of the snow around and as a result we have a mix of ice,deep drifts and windslab on many aspects, mainly above 800 metres. Currently there are very deep accumulations on West to Northerly aspects which have weaker layers and are sitting on hard icy bases.
This week has been windy with snow showers throughout. Although there is very little snow below 800 metres, above 850 metres or so there is good cover. Windslab has been mostly on NW through to E aspects all week with avalanche debris noted on some of these aspects. Fluctuating temperatures has helped with consolidation but instabilities were persisting in many locations.
From around 750 metres there has been a well bonded and stable snowpack for most of the week. Towards the end of the week there have been two periods of fresh snowfall that were followed by a rapid thaw and subsequent refreeze of the snowpack.
A number of thaw freeze cycles, which were slowly stabilising the snowpack, was followed by a more substantial thaw. This left a moist soft snowpack at all levels which was then frozen as the freezing level dropped again. Currently we have good firm cover above 850 metres on most aspects.
It has been an unsettled period with strong winds mostly from a SW,S and SE direction and a mix of snow showers and rain. Areas of windslab developed on mainly W through N to E aspects above 900 metres. Stability has been improved due to a number of thaw-freeze cycles but some weaknesses persisted in deeper deposits on steep terrain. Generally there is now good cover above 800 metres which is icy in come locations.
A complicated week with snowfall, very strong variable winds and a quick melt freeze cycle. Windward slopes are scored whilst lee slopes have filled in with sheltered locations holding deeper snow. Another weather event is imminent with conditions changing daily.
There wasn't really too much to get excited about up until 24 hours ago. The last storm on Wednesday evening gave us a good amount of snowfall at most levels. The winds with this snow were very strong, 100 mph recorded on Cairnwell. So anything exposed is wind blasted, anything sheltered has reasonable depth of snow. Lower parts of gullies are still quite bare but at least the upper parts are starting to fill in.