Soft cornices.

Last nights wind and snow has formed some large and fragile cornices. These are prone to collapse both spontaneously, or if disturbed, and can easily release the windslab on the slope below. Unfortunately the light was very flat, and you can't see much in any of the pictures that I took of the cornices. However, the picture shows the side/crown wall of a cornice triggered slab avalanche (notice the rope, I approached this safely via a short abseil from the top). Although this was not a large avalanche in the grand scheme of things (the release area was about 8m across), it would have easily have sent you tumbling should you have been climbing/walking below. Another such crown wall was just visible further along.

If climbing in these conditions it is wise to consider what is above you what is above your route, and avoid gullies with big cornices/areas of windslab above. With a bit of consideration and forward planning (some local knowledge helps as well though) routes which are safe from such objective dangers can almost always be found.

Avalanche on Aonach Mor

On the way up Aonach Mor this morning we heard reports of a "wee slide" being triggered on the West Face at the lowly altitude of about 600 metres. We had been planning to head to that sort of area anyway, so we decided to go and investigate. What we found was a hard slab avalanche had occurred. It was about 50 metres wide, and had run about 200 metres down the hill side. The crown wall reached a maximum depth over a metre, and was 50cm to 1 metre deep from most of it's length. A bit bigger than a "wee slide" I thought. The avalanche had run on a deep and particularly hard layer of small rounded crystals. Today's snow profile is a profile of the crown wall.

Looking south to where the crown wall height was at it's greatest (about 110cm). The first two pictures were taken from the location of the figure in the third picture.

Investigating the crown wall.

Looking back north along the crown wall, it is not too clear but it continues beyond where the figure is. This photo was taken from just below where the figure is in the first picture.

Blowing snow.

Even a seemingly uniform layer of snow will contain many mirco-layers, created by constantly changing conditions as the snow was deposited. Usually these are not too evident, but the strong winds blasting this block of windslab that I dug up really made this micro-layering visible (the horizontal bands).

There was a strong wind on Aonach Mor today. It was very variable in directions, redistributing the existing snow around the mountain. This means that there are pockets of slab on many aspects.

Shearing layers

Three very clean shears came out today when doing a tap test on at the top of the West Face of Aonach Mor. The lollipop sticks were included to mark layers shear, although they are pretty obvious in this case. I am not sure whether you will be able to read scale on the ruler, but in this test these shears occurred at a depth of 12, 20 and 33 cm. This photo was taken on a low angled (about 15 degree) slope with a Westerly aspect. I would be very wary of going onto any steep, snowy slopes with this aspect at the moment.

Looking into Coire an Lochan today. A fair bit of snow on the East Face of Aonach Mor as well.

Deep drifts

Keith looking at one of the big drifts in the summit plateau at Aonach Mor. There are several of these deposits on the summit plateau formed from the wind erosion from the big easterly corries. This one is almost 2 metres deep

More good weather

Another beautiful day in Lochaber!

Facets.

The cold and generally settled conditions have continued in Lochaber. Normally snowpack stability will improve during settled periods. However, due to the consistant low temperatures of late, a strong temperature gradient has developed within the snowpack. This has caused a process called faceting to occur within certain layers. This process is due to vapour transfer within the snowpack and causes the crystals to become angular in shape, and have a sugary consistancy. These layers are very weak, and in many locations are covered by a layer of windslab.

In the picture a crack shoots out from my feet (a sign of poor stability) on an easy angled slope at the top of the West Face of Aonach Mor. Very weakly bonded areas of windslab were also observed on the East Face. Although no spontaneous avalanches are happening at the moment, there is potential to trigger avalanches on slopes of almost any aspect.

Have a good new year and be careful folks.

Blair

Cold and settled

Conditions have been cold and settled for a few days now. Great for the festive holidays. Here are some pictures from on and around Aonach Mor over the past few days.

Looking over to Carn Mor Dearg and Ben Nevis today.

The crags in Coire an Lochan are pretty buried. I think the routes here would be pretty hard work with a lot of clearing required.

There are a few cornices around as well.

Surface hoar forming in the cold, settled conditions (for scale the larger grid on the crystal card is 3mm). These sparkly little crystals are the cause of many avalanches in the Alps and North America, where they get buried by subsequent snow falls, and become a weak layer/sliding surface. They are less common in Scotland's maritime climate, but now they have formed in some locations they could easily become significant if we get a large snowfall before they are destroyed by either high winds or a thaw.

Very quiet up the Ben today with only 2 parties visible: Point five and Castle Ridge.

Underfoot its still deepish unconsolidated snow

Spot the climber in Point Five today

Happy Christmas

Happy Christmas from snowy Glen Nevis looking up towards Meall Cumhann and the West face of Aonach Beag

A new Season

Is the weather about to clear up.....

Well it has been a wintery start to the avalanche forecasting season. The past few days have been cold, with summit temperatures of around minus five and fresh snow down to sea level. For a short time this morning it looked like it was about to clear up on Aonach Mor, but suddenly the wind got up and it started snowing. At the summit hut I met two climbers who had originally planned to descend Easy Gully into Coire an Lochan. However, with a fair bit of soft windslab about, and the poor visibility, they sensibly decided to head over to the West Face (often a safer bet when there is a substantial avalanche hazard in Coire an Lochan).

Discussing options at the summit hut

Heading away from the top of Coire an Lochan in some wild weather.

Just about the end

Filming for Countryfile. Showing Julia Bradbury that avalanche forecasting is not as glamourous as some may believe.

Well it's just about the end of the season here in Lochaber (the last report will be published on Friday) and this will probabely be the last blog post.
During the past few days Countryfile been doing some some filming in the area, including the work of the avalanche forecasters. This will shown next Sunday at 7pm on BBC1.
Also on Sunday there will be a Seminar on the Provision of Avalanche Forecasting in Scotland at Glenmore Lodge. More information can be found on the SAIS website.
See you next winter.
Blair

Still Plenty of Snow in Lochaber

There is still a fair bit of snow about on high East facing aspects in Lochaber at the moment.

Boarding down Summit Gully. Conditions looked good.

Still some large cornices about.

It was so nice that pac-man quit his 80's computer game, joined up with spider man (on the tow) and came up with some boarding.

The Aonach Mor Crevasse.

Debris from an avalanche almost down to the loch.

It was mild, but thankfully quite dry on Aonach Mor today. Debris from an avalanche, which probabely released on Wednseday night or Thursday, was observed almost down to the lochan of Coire an Lochan. The crown wall could be seen at the top of Easy Gully. This was a vertical drop of about 350 metres.

Taken from standing in a rather deep crack in the snow. The overhanging natural of the walls meant that it felt about grade VI to get out of.

In the mild conditions some large creep/slump cracks are starting to form. This one was covered by a soft layer of snow until being "discovered" my assistant, it gave her a bit of a shock.
Blair

Lots of snow high up.

Lots of little sluffs in Coire an Lochan, probabley from yesterdays snowfall.

Still a few chunky cornices about. I would be very wary about being below one of these on a mild day.

Firstly sorry about the long time period since we last blogged, out camera got misplaced for a while. Have got it back now. Although it may not appear this way from the glens, there is still plenty of snow about high up in Lochaber. Conditions on many of the easy and mid grade gullies and ice routes high on the Ben and Aonach Mor are probabley quite good, if a little soft in places, at the moment. What's more the crags are very quite (there was nobody climbing in Coire an Lochan of Aonach Mor today) and there is loads of daylight so you don't even have to get up that early. Snow stability has generally been pretty good recently, but this can change rapidly if we have a big dump of fresh snow. Also be wary of cornice collapse and ice fall on those mild days.
Blair

Avalanche cake.

Damp, mild and windy on Aonach Mor today, hopefully a return to colder conditions on Monday

It was not very inspiring weather in Lochaber this weekend. Saturday started cloudy, cleared up for a while in the afternoon before staring to drizzle again in the evening. Sunday was windy with showers which fell as rain at all levels. The freezing level remained above the summit and so the snowpack continued to thaw.

The avalanche cake.

So to make up for the lack of interesting snow, we baked an avalanche cake. A three layers victoria sponge was used to create the underlying mountain shape. The top layers of this are cut up and placed in the approiate location to form your favourite avalanche track. The snowpack is made of regular white icing. The avalanche and debris is a mix of royal icing, and mini marshmallows. For extra realism (you can just make it out in the picture) a layer of surface hoar was created using edible cake glitter.
As well as being both fun and educational, such a cake is good tasty fuel for those of us whose job it is to look for real avalanches.
Blair

Aonach Mor in the sunshine

From the South

From the North.

Spring has sprung

Morning Slab, Ben Nevis with that nice water smear running down it

Looking further into the Corrie where much of the action was today. Many teams also on the ridge lines

Spring has Sprung.

Looking over to Ben Nevis.

Topping out on Right Twin.

For the first time this year it really felt like spring in Lochaber today. While wandering along the top I noticed my friend Rob topping out of Right Twin. He reported good conditions in shady locations, but things begining to soften where exposed to the sun. There are some large cornices about, and although they were generally stable today, they made topping out in some loactions quite awkard. Conditions were looking good over on the Ben.
Blair

Drooping cornices

Long crack appearing well behind the corniced edge.

This section of cornice is unlikely to be there for long. In fact I am sure that the crack you can see was getting wider in the time we were there.

Ben Nevis yesterday (14th March). A fair bit of ice high up.

Conditions have been mild for the past few days. Cornices are slumping, cracking and prone to collapse, as these pictures indicate. There is a fair amount of ice on the Ben. It is thawing at the moment, but what is left if/when it freezes should be good.
Blair

The Ben

Freezing level has lowered to around 1000m on the Ben today. Looking pretty thin low down. The Curtain has all but disappeared.

Quite a lot of recent debris below No 2, 3 and 4 gullies

The Ben

The Ben has a distinct winter feel about it with masses of fresh snow up high. Many of the lower routes are a bit on the thin side

Team Hopeful having a look at the Curtain

Its all down to route choice in the end. Various teams I spoke to today were all slightly agast at the scene below. Now they may have had some divine information as to the stability above, but I rather suspect not. Hopefully they survived, but if they did, it would be down to a lot of luck and not good route choice.

Team Suicide head up Number 2 Gully

It is often said that "Buttresses are a safer option" The team below have certainly taken this to heart! See if you can spot them

Team Steep on Sassenach

Weak Cornices.

The section of cornice which collapsed yesterday, with the debris in the background.

One section (further away) collapsed, while the other (foreground) section cracked, and settled a bit, but did not release. This failure was caused by stepping onto the location that this picture is taken from. When cornices are as weak as this, sometimes just approaching them can cause their failure. Other hill goers reported similar behaviour yesterday.

Yesterday there were some large cornices noted on Aonach Mor. This one collapsed when I skied a little too close. A climber was injured in Coire an Lochan, when he fell off when trying to surmount one other these cornices. Although the cornices were very unstable, the snowpack on the slopes below seems more stable. This cornice collapse failed to release the slope below. As the avalanche report indicates general snow stability, rather than specific cornice collapse hazard, a category 3 rather than a category 4 hazard rating was issued (although the cornice hazard was mentioned in the text).

Today the weather was very different with rain at all levels. Although all the cornices we observed today were still intact, but it wont be long before they begin collapsing due to the mild conditions. Also the stability of the large quantities of windslab about, will be dreceasing in the rain. All in all, an unpleasant, and potentially dangerous afternoon on the hill. However, a freeze is forecast for tomorrow, which will improve climbing conditions , and make travel around the hill alot easier.
Blair

What a difference a day makes,

Smile folk, it's snowing.

Yesterday (Monday) I was verging on losing the love for Scottish winter. Two weeks of mild weather, and then snow that was forecast, turned out to be rain all the way to summit level. To make matters worse, I slipped on some wet grass and ended up falling face first into some slush.
Today (Tuesday) things were very different. Heavy snow was falling at all levels, with the ski runs filling in nicely. Visibility was poor, so I could not see much on the tops. I imagine the climbing conditions will be improving, although some careful route choice is recommended as some large fragile cornices exist, and scarp slopes are likely to hold some poorly bonded snow. The fresh snow is quite soft, so in some places walking is quite hard going, but I think this is a small price to pay for a return to winter.
With the longer range forecasts predicting wintry weather all week, I have decided that maybe Scottish winter is not so bad after all.....
Blair

Winter returns

A party making their way up Coire Dubh, There was a bit of fresh snow here, but no real cornices. In other locations some large and fragile cornices have formed.

Winter made a return to Lochaber today. There was quite alot of fresh snow in the tops. Some soft cornices are forming. On Aonach Mor the area around Coire an Lochan didn't seem too bad from an avalanche point of view, with many people heading down Easy Gully no problem . We then headed over to the top of Summit Coire, the next coire to the south. Despite a similar altitude and aspects, there seemed to be more fresh snow here, and some substantial cornices were observed. A careful investigation revealed these were soft and prone to collapse.

Some wild and snowy weather expected tomorrow.
Blair