Avalanche Report for Northern Cairngorms
Avalanche Hazard Forecast
FOR PERIOD 18:00 Thu 18/12/2014 TO 18:00 Fri 19/12/2014
Forcasted Snow Stability & Avalanche Hazard
Accumulations of unstable windslab will form on North-East to South-Easterly aspects mainly above 750 metres where avalanches are likely, Northerly and Southerly aspects will also be affected due to the cross loading of snow into wind sheltered places. Remaining bare and scoured on West aspects. The avalanche hazard will be Considerable
Forcasted Weather Influences
Winds will be very strong West-South-Westerly then Westerly with snow showers, sometimes heavy down to 300 metre levels. Freezing levels around 500 metres.
Key Snow Stability Observations
Observed Avalanche Hazard -
Observed Weather Influences
Strong Westerly winds with gradually increasing levels of precipitation falling as snow on the tops. Freezing level above summits at first gradually lowering through the day.
Observed Snow Stability and Avalanche Hazard
The snowpack has slowly consolidated and is generally stable throughout, some instabilities remain but these are confined to isolated locations in the steepest places on North-East to Easterly aspects above 950m. Some drifting of new snow has started to accumulate deposits on these aspects also but are not significant. Bare and scoured on West aspects. The avalanche hazard is Moderate
Storm force winds with snowfall and blizzards expected.
Storm force westerly winds and significant snowfall at the start of December produced unstable conditions. Warmer periods with rain to summit levels has diminished the snowpack and a slow consolidation and stabilisation has taken place. The arrival of colder conditions and snow fall thursday evening will present another period of instability.
Snowpack is diminished in extent but remains in large areas above 800 metres on mainly North to East aspects. Snowpack continues to undergo freeze thaw cycles and remains dense firm and stable throughout.
The snowpack is gradually diminishing and is generally well bonded and stable in all locations. Glide cracks continue to widen on many steep slopes and remaining cornices prone to spontaneous collapse.
The snowpack has progressively become more dense and consolidated as the week has progressed and is generally stable throughout the area. Cornices have presented a continual hazard and their stability remains very unpredictable.
Cold temperatures and new snowfall created an unstable snowpack in isolated locations at high levels at the start of the period. Thaw and re-freeze stabilised the snowpack completely midweek. New snowfall with strong wind has presented poorly bonded windslab on limited aspects mainly above 900m at the end of the week.
Diminished snowpack with rain to all levels and freezing levels above the summits during last week. Snowpack though has compacted, is dense and generally stable even though soft in places. Cornices have always remained a threat. Cold temperatures have started to re-freeze the snowpack at period end. Fresh windslab beginning to build.
The snowpack has been thawing at all levels leading to a mostly stable snowpack with some surface instabilities in areas of steep terrain. Earlier in the week weakly bonded windslab consolidated after a thaw. light snowfall followed this with localised weakly bonded accumulations developing above 1000m. This has since thawed and consolidated.
Freeze then thaw conditions continue to effect the snowpack, calm but snowy conditions at the start of the week presented a weak layer once it became buried, this was still present at the end of the week but rain and thaw conditions followed by a re-freeze has improved this situation. New snowfall and wind presents new windslab hazard.
Old snowpack has gone through thaw and then freeze cycles and has become generally well bonded and stable. New accumulations of fresh snow present surface instabilities in steep wind sheltered places but these tend to improve with fluctuating temperatures and if calm periods persist.
Storm cycles followed by more settled weather, leaving instabilities at depth on steep convex terrain. A thaw at all levels followed with wet snow avalanches, now the snowpack is beginning to consolidate again in cooler temperatures.
Storm cycles continuing, very windy and cold. Periods between storms where snowpack stabilised but more heavy snowfall, with drifting creating new hazard. Some sugar like weak faceted crystals have developed due to cooler temperatures over the last few days.
Continuing storm cycles with cold and very windy conditions, heavy snow and drifting presenting very unstable snowpack situations. Snowpack beginning to stabilise during calm periods but new storm cycles present new avalanche hazard.
Strong South-East winds have predominated producing heavy drifting and deep windslab accumulations. Calm but snowy conditions midweek produced a weak layer. This is now covered by windslab to varying depths and presents a persistent weak layer and an unstable snowpack.
Continual Southerly winds with snow have built significant windslab deposits on all Northerly aspects, very unstable at start of week. Cycles of thaws to summit levels then freezing conditions Improves snowpack stability but new instabilities and weak windslab soon follow. A dynamic and unstable week.
Thaw then re-freeze cycles have stabilised the snowpack in all areas. Localised, progressively weakening windslab that was present earlier in the weak has therefore been stabilised. New windslab formations are developing on Northerly aspects.
A week ago, conditions were very unsettled with snowfall and Strong mostly Southerly winds. The snowpack was weakly bonded especially above 900m on NW through N to E aspects. Avalanches Occured on Northerly aspects. This was followed by melt freeze cycles which aided snowpack stabilisation. Now the snowpack is generally well bonded in most locations. Small pockets of windslab lie on N to W aspects above 950m around corrie rims and gully tops.
Continuing windslab formation with strong winds on mainly North West through North to East aspects above 950 metres mainly. Brief freeze thaw cycles affect windslab with surface crusts and only partially bridge the weaknesses that remain at depth. Corrie rims, gullies and convex terrain affected.
A week of strong winds and snowfall, with thaw freeze cycles mainly below 900m; however extensive weakly bonded accumulations of windslab have been affecting mostly NW to NE aspects above 850 metres leading to Considerable conditions in these areas and generally moderate below this altitude with localised Considerable in lee areas.
Old snow has been refrozen. New deposits of wind slab have been deposited on North to North East slopes. Deep drifts of fresh snow interspersed with scoured patches of hard snow. The general cover is still sparse.
Limited snowpack, patchy and stable