Avalanche Report for Southern Cairngorms

Issued

Avalanche Hazard Forecast

FOR PERIOD 18:00 Sun 08/05/2016 TO 18:00 Mon 09/05/2016

Hazard level
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Low
Human triggered avalanches not likely. Generally safe travel conditions.
Moderate
Human triggered avalanches are possible, so good visibility and good route selection is important, especially in steep locations as indicated in the reports. Groups should be managed carefully, keeping good spacing between people to reduce loading on slopes.
Considerable
Natural avalanches may occur - and a single person load is likely to trigger an avalanche on some slopes. Good visibility and route finding in mountain terrain is important, as is experience in avalanche hazard evaluation.
High
Natural avalanches will occur - and a single person load will trigger an avalanche on some slopes. Good visibility and good route-finding in mountain terrain is essential, as is experience in avalanche hazard evaluation.
Very High
Widespread natural avalanches will occur - and a single person load will trigger an avalanche on most slopes. Good visibility and good route-finding in mountain terrain is essential, as is experience in avalanche hazard evaluation.
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Forecast Snow Stability & Avalanche Hazard

Snow fields remain in all mountain areas above 800m, sometimes extensive above 1000m in the Cairngorms and Ben Nevis areas. These will continue to present a slipping and falling hazard if firm and icy. Cornices threaten many slopes and are unpredictable and prone to collapse in the warm spring conditions also, the potential for full depth avalanches due to snow creep producing Glide cracks in deeper accumulations on steep East facing slopes also presents an unpredictable hazard.

Forecast Weather Influences

Key Snow Stability Observations

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Observed Avalanche Hazard -

Observed Weather Influences

Observed Snow Stability and Avalanche Hazard

Mountain Conditions

Comments

Weekly Snowpack Summary
  
  • It has been a week of gently fluctuating temperatures with the freezing level rising and lowering around the summit levels. The snowpack has been generally well bonded and stable but snow showers have produced localised accumulations on various aspects. Generally these have been shallow in nature but occasionally slightly deeper deposits have formed in steeper, sheltered locations. The highest mountains and plateau areas have good cover above 900 metres: At present this is firm and icy.

    There was an unstable start to this period with avalanches overnight on the 1st. After this there was light snowfall most days but the freezing levels fluctuated with snow to various levels. New accumulations tended to be shallow with some isolated deeper areas. Stability of new snow remained reasonably good with only surface instabilities noted on steep terrain. The older snow was generally soft but remained stable throughout the period. Glide cracks are developing in many locations.

    At the start of the week there was a stable Spring snowpack. On Saturday 26th there was snow on the higher summits but heavy rain at most other levels, with a number of cornice collapses. After this most days saw new light snowfall to around 650 metres with a blanket of new snow over most aspects. This has generally bonded well to older hard snow-ice with new localised accumulations forming mainly on NW to NE aspects above 900 metres, often at the top of Corries.

    The snowpack has been diminishing all week, often soft at lower levels but remaining generally well bonded on all aspects. Overnight on the 23rd, freezing levels dropped and there was some new snowfall above 800 metres. Accumulations were generally very light with isolated deeper pockets on N to E aspects. These were not significant enough to alter the avalanche hazard which remained Low. Creep lines continue to widen in older deep accumulations on steep convex slopes.

    Unsettled conditions at the start of the week with unstable windslab on NE to SE aspects. A thaw on the 11th produced widespread avalanche activity. The mild weather continued through the week with gradually improving stability in a diminishing snowpack. High pressure at the end of the week has produced some glorious weather with the generally stable snow thawing during the day and refreezing at night. Cornice collapse and rock fall has been a feature of the week.

    The week started with unstable windslab on East through South to West aspects. Avalanche debris on some of these aspects was noted towards the end of the week. On the 7th the dry, light snow was redistributed onto North to South-East aspects. Accumulations on these aspects are deep in places. A strong Northerly airflow on the 9th lead to further redistribution with avalanche activity noted on a SW aspect. On the10th the freezing levels started to rise and are forecast to be above the summits.

    This week was dominated by high pressure with cold and dry conditions. Weaknesses persisted deeper within the snowpack but an overnight thaw on the 1st March, with some avalanche activity, helped stabilise conditions, particularly as freezing levels dropped again. There was heavy snowfall on the 2nd March with new windslab building on NE to SE aspects. These light, dry deposits will be easily re-distributed in stronger winds over the next couple of days. Expected to remain wintry into next week.

    It has been an unsettled period with very windy weather for most of the week. Snowfall and drifting on the 19th led to avalanche activity being observed on a NE aspect. There was a quick melt/freeze cycle on the 20th with cornice collapse occurring. Further snow showers and very strong winds continued the cycle building windslab in sheltered locations on NE through E to S aspects, leaving the West and North-West aspects scoured and very icy. The week ended with high pressure building.

    Generally a cold week, starting with strong winds and drifting. Heaviest snowfall occurred overnight on the 13th with a number of natural avalanches reported on West aspects. Storm force winds on the 16th Feb re-distributed softer deposits again. There was also a brief thaw later that night which has helped stabilise the snowpack when freezing levels dropped. Currently many areas are firm but some with deeper weakness and shallow windslab developing in sheltered areas.

    It has been cold all week with new snow falling mainly on the 6th and 7th. Strong, changeable winds has led to a lot of redistribution with unstable windslab developing on most aspects during the week. Generally, stability is slowly improving, many areas becoming scoured and icy and windslab becoming restricted to sheltered steep terrain. Currently new accumulations are forecast to develop on South to South-West aspects.

    It has been a very unsettled week with freeze cycles and a mix of snow and rain, which in general has helped consolidate most of the snow cover. Localised unstable windslab was generally restricted to steep, sheltered terrain on North through East to South East aspects above 800 metres. Winds were very strong and often variable with Storm Henry stripping most of the softer snow from the hill. Remaining cover is scoured and icy and currently subject to another thaw freeze cycle.

    Thaw conditions for the first part of the week, severely diminishing cover below 700 metres. Generally had become stable, apart from isolated instabilities on steep terrain. Tuesday to Thursday were cooler with new snowfall and improved cover from 600 metres. However, strong winds have led to new windslab developing, mainly on N through East to South-East aspects above 800 metres, with some deep drifts at lower levels. Fluctuation in the freezing level is forecast with a mix of rain and snow.

    This period started with significant Northerly winds after which it was calm with light snow and overall cover remained excellent. Weaker layers were noted on steep terrain on most aspects but were supported by harder denser snow above them. There was a temperature gradient in the cold, dry snow for most of the week and developing facets were noted. Strong winds today with deep unstable windslab developing on Northerly aspects. Currently rising freezing level with rain due later

    Frequent snow showers gradually eased to give light snow and then dry days. Winds travelled all the way through the directions and have been variable in speed. The freezing level has gradually lowered to become very cold at the end of the week. The outcome of these influences is near full snow cover on all aspects down to 600 metres. Consolidation has been delayed by the very cold temperatures and deposits have remained available for redistribution in the variable winds. Instability persists.

    Persistent precipitation all week, generally falling as snow from around 600 metres and accompanied by a strong Easterly airflow, has led to significant quantities of windslab on the hills. Stability remains poor on steeper slopes but there has been some consolidation elsewhere within the snowpack. Visibility has been poor with one avalanche noted at around 750 metres.

    The week started well with cooler temperatures and some new snowfall but then ended with thaw conditions and finally Storm Frank. Heavy rain and mild temperatures significantly depleted the snowpack leaving patchy areas in the the most sheltered locations at higher elevations only. These snow patches are currently refrozen and very firm.

    It has been mainly mild, wet and windy. At the start of the week there were limited patches of soft, wet snow in the higher gullies lines or around corrie rims. Towards the end of the week the temperatures lowered and produced some some showers giving a more wintery appearance and some isolated accumulations of deeper snow. However an overnight thaw at the end of the period has reduced the cover back to patchy areas in sheltered locations on mainly North to East aspects from 900 metres.

    The week started with fairly significant thaw conditions (plus 8.1 degrees at 880m) rapidly reducing the snow cover. A return to cooler conditions with some precipitation gave a more wintery appearance in the middle of the week. However we end the week with all the superficial snow having thawed and patchy cover mostly above 900m on mainly NW through NE to SE aspects. Greatest amounts are present in the high North and East facing corries with some large cornice remnants still present.

    It has been a dry and mild week and apart from the first two days, sunny and clear. Last weeks deep accumulations were soon gone in the warm temperatures, over +12 degrees recorded at 1000 m on Sunday. Surface instabilities, cornice collapse, rock and ice fall were commonplace but nothing significant has been observed despite the clear conditions. Cover is much depleted, patchy on all aspects with wet ground at all levels, burns and rivers flowing well but not full.

    It has been an unsettled week, initially with new localised marginally stable accumulations developing over older snow. Heavy snow mid-week, down to valley level, buried already poorly bonded snow leaving weaker layers at depth with the hazard also becoming more widespread. A number of smaller avalanches occurred. Currently there is reasonable cover above 800 metres with deeper accumulations on NE to SE aspects. The freezing level is forecast to rise over the weekend.

    Mostly a sunny week with spring like conditions. Fluctuating freezing levels ensured older snow remained stable, becoming very firm and icy at times. Snow cover is patchy, some burn lines but mostly North to East facing corries hold greatest amounts. More significant snowfall arrived on Wednesday night. Many locations where accumulations developed were bare ground but where it overlies old snow it had not bonded well on steeper terrain. Snow under 900 metres had started to thaw by afternoon.

    Generally the snowpack has been well bonded with at times pockets of snow developing in wind sheltered locations, however these were not deep nor extensive. The last couple of days have been very mild with with the snow now thawing at all levels. Overall stability remains good but one avalanche and full depth avalanche was noted on an East aspect starting around 1000 metres.

    During the first half of the week the snowpack diminished in the milder conditions. Cooler conditions with some snowfall in the second half of the week refroze the old snow and produced some windslab accumulations in sheltered locations. Currently, any shallow snow cover is thawing in the rain as the freezing level has just risen over the summits. The remaining snow is patchy and generally found above 900 metres, with deepest amounts present in the North and East facing corries.

    It's been a mixed week for snowfall and freezing levels giving a series of thaw-freeze cycles, all accompanied with strong SW to NW winds . New accumulations were often light with the heaviest snowfall of the week on the 3rd. The 4th was a sunny and later calmer day with surface instabilities on sunny aspects. Snow cover has started to diminish and is largely soft and moist. E aspects have good cover with W and exposed ridges heavily scoured.

    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.

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