February 10, 2010
Synopsis;
RAIN! Rain! rain…
Over 24 hours of fairly solid rain up to 2000 metres here in the Hakuba Valley. 36 hours of rain come 0700; 100210. This has of course seen deep penetration of the dry virgin powder that we had only 2 days ago turn into a metre of wet and moist (↓０−１００cm) riding on top of a stiff slab (↓１００−１５０cm) over a low density sandwich with the old rain crust (210110 / 280110 MFcr↓１５０) that continues to grow facets and loose cohesiveness. The mountains will be flushing the weighted wind and soft slabs that did not come down in the last storm now that they have been super saturated by the present stationary front.
Avalanche Activity;
There were multiple natural slab avalanches on all aspects but the east, north east aspects, in steep convex terrain below trees, rocks and cornices have proved the least stable of the slopes pre the rain. Due to low visibility from valley bottom today not many avalanches, other than Roof slides that proved to be fast, heavy and sets up very quickly, were observed but are expected through the duration of the rain and after until the surface re-freezes.
Travel Advisory;
Stay out of the backcounrty, stay to the groomed piste or make it a clean up the house and have an onsen day. But if you must go into the backcountry stay to very low angle slopes, stick to the ridges and be aware of hazards above you. Stay well back from cornices as they are heavy and will step back at least twace as big.
Avalanche Hazard:
Alpine: High
Tree Line: High (Trending to Extreme with continued rain)
Below Tree Line: High
February 6, 2010
Synopsis;
Due to Heavy snowfall in the past 4 days and recent overnight winds the Hakuba mountains are growing more unstable by the hour. Temperatures are cooling and winds at ridge top are Strong to Extreme from the North West hence intense loading on lee slopes as well as cross loading occurring. Increased snow loading adding stress to weak layer at 100128 MFcr (Melt-freeze crust). Probable laminate wind slabs in HST (storm snow) resulting in surface avalanches as well as possible deep slabs sliding on the Melt-freeze crust.
Avalanche Hazard:
Alpine: High
Tree Line: High (Tending to Extreme if the rain continues.)
Below Tree Line: High
100205, 1245, 1800m, NE aspect Happo; Ochikura, 35 degree slope angle, SB (snowboard) triggered Slab, size 2.5 avalanche, 80cm – 150cm Crown, 50 m propagation, 200m length, MFcr bed surface
Multiple Natural Slab avalanches, size 2 – 3, N & NE aspects in Happo Alpine and treeline area.
Travel Advisory;
Travel not recommended at tree line and above due to High avalanche risk because of High winds and heavy snowfall adding rapid loading on weak buried MFcr (all aspects), creation of cornices and intense wind loading on lee slopes (S & SE aspect). Stay Below treeline on low angle slopes / simple terrain. However; Slope angles less than 30 degrees will be difficult to navigate due to deep snow and therefore travel will be slow and time exposed to possible hazards will increase. Caution is needed in these deep snow areas as if you fall you may not be able to get yourself out especially terrain trap areas like deep gullies and tree wells. Due caution on windward aspects due to creation of wind slab.
It is advisable to enjoy the great powder snow in bounds and stay out of ‘Out Of Bounds’ areas and the back country all together.
Avalanche Hazard:
Alpine: High
Tree Line: High
Below Tree Line: Considerable
February 1, 2010
Avalanche Observations 310110:
Happo Sawa 1800m ~2000m Multiple (5) Size 1.5~2‚ S on NE aspect in steep gully terrain. Bed surface (滑り面) ice crust. New storm snow released NATURAL on seemingly cross loaded gully features during the night or at first light. Debris ran to middle of run out.
Karamatsusawa‚ 1200m Multiple size 1‚ L on S aspect and 1 size 2‚ S to the ground (前奏) just above ski out at usual ski change up area below summer access road to water reservoir. Could have been dangerous as it is a high use area.
Kuzurisawa‚ Multiple size 1‚ L on S aspect and some old size 2‚ S on S aspect at 1600m ~1200m.
Tests:
CTHB(27)down 90cm on DF size 1 on NE aspect at 2200m on 33 degree slope. Hand test showed easier results and seemed more sudden.
Synopsis:
There is still a solid wind slab over lighter density snow down 50cm ~ 90cm‚ on N and NE aspects that could still pose a problem‚ but things seem to be bonding quickly. There is‚ however‚ still the chance to get surprised by big slabs on big terrain features in steep stressed areas.
S and E aspects are experiencing a lot of glide cracks. It is possible that the moist snow on the ground is continuing to slide and dry slab on top is being stressed and could fracture due to this phenomena and continue to S avalanche when unexpected.
Travel advisory:
Stay to supported planar terrain features when possible and avoid steep side loaded terrain‚ large convexities‚ steep solar radiated rocks and trees as well as cornices. Watch out for wide glide cracks and holes in the snow.
January 31, 2010
Synopsis:
On investigation into the Alpine yesterday during extreme wind conditions it was more than obvious that we had intense blowing snow at ridge top and even below ridge line. The South East aspect are heavily loaded and scouring down to the rain crust of the 28th on wind ward slopes. Once again great spacial variation across the mountain. Melt Forms were not found in the upper 120 cm of the snow pack at 2000 metres in a heavily loaded lee slope, however, when probed a lower density layers were found at 130cm and 160 cm down. The 160 cm layer was right above a thin melt-freeze crust. Compression Test at this location (very difficult in the extreme winds) found a CTM Resistant sheer at 50 cm down and further CTH breaks and resistant planar sheers below this in wind loaded snow.
At lower elevation (1450 m) the Rain layer of the 28th was apparent below the new HST storm snow and reactive in Compression Tests on NE aspect CTMPC(12) down 35cm on DF size 1. The rain layer at this elevation was still moist and retaining heat with temperature of 0*C. There was also results above the Jan 21 Rain Crust CTHSP(22) down 90 on DF / RD size 1. The most concerning find was the moist melt forms in the lower half of the snow pack to the ground that will not be freezing as the overall temperature of the snow pack is hovering around 0*C. This lower moist snowpack is resulting in large glide cracks seen at lower elevations and at the ski resorts. Todays warming temperatures and strong solar radiation will not being doing anything to alleviate stresses on these lower layers and could result in slides to ground on steep solar radiated slopes around rocks or trees at lower elevation (1500m ~ 800m).
Travel Advisory:
Use extreme caution when crossing solar radiated lee slopes and cross loaded slopes in steep tensioned terrain or avoid all together during periods of strong solar radiation and mild temperatures. Stay to supported and simple terrain away from cornices and convexities. Watch out for solar radiated hazards from above on traverses out in the valley bottoms and holes over creeks that may be opening up after recent rain and warm temps.
Hazard Rating:
Alpine: Considerable (Cornices, Lee side loading, Steep solar radiated rocks)
Tree Line: Considerable (Cornices, Lee side loading, Steep solar radiated rocks, trees and convex rolls)
Below Tree Line: Considerable (General warming of entire snowpack, Steep solar radiated slopes)
January 29, 2010
There were reports of naturals from steep low elevation terrain around cornices and glide cracks as well as a reported skier triggered slab avalanche below tree line‚ 1100m‚ Happo One Ski Resort north aspect. Size 2‚ 100cm crown‚ wide slab propagation‚ 100 metre plus length of slide‚ 200cm deposit at the toe‚ non burial. Suspect weakness was due to rapid increased load of rain on the well bonded past Stm Snow of 100110~100115 over riding persistent buried surface hoar / facets.
The rain layer has now had time to freeze on the surface in to a melt freeze crust‚ however‚ there are still some areas with remaining wet grains (Melt Forms) under the crust. These melt forms will stay wet or moist in lower elevations until temperatures remain cold enough to freeze through the whole pack.
The past 3 days have brought 30cm in the valley and more at elevation along with strong winds in the Alpine and at tree line that has deposited greater amounts of snow on the East and South East lee slopes. There are now areas of wind slab and exposed rain crust; extreme spacial variation.
Travel advisory:
Take due care in avalanche terrain as new snow accumulates and stability decreases through wind transport and the creation of slabs. Watch out for unsupported steep cross loaded slopes and leading in from shallow snow areas where the wind slab will be more reactive and easier to trigger. Be aware that Cornices are once again growing and will be tender. Stay away from cornices all together. And remember to travel with partners in the backcountry.
January 24, 2010
Well, we did receive that mixed bag that was forecasted; Rain starting the evening of the 20th this rain fell on all ski areas to the top lifts from 18:00 100120 to 09:00 100121 and also to 2400 metres for a short period of this time and sleet or wet snow before the freezing level came down to the valley floor by 10:00 100121 to put rapid loading on the snow pack on all aspects at all elevations. This was followed by strong NW winds and rapidly cooling temperatures and continued snow. The rain penetrated anywhere from 20 cm to 40 cm into the snowpack depending on elevation and aspect.
There were reports of naturals from steep low elevation terrain around cornices and glide cracks as well as a reported skier triggered slab avalanche below tree line, 1100m, Happo One Ski Resort north aspect. Size 2, 100cm crown, wide slab propagation, 100 metre plus length of slide, 200cm deposit at the toe, non burial. Suspect weakness was due to rapid increased load of rain on the well bonded past Stm Snow of 100110~100115 over riding persistent buried surface hoar / facets.
The rain layer has now had time to freeze on the surface in to a very strong melt freeze crust, however, there are still some areas with remaining wet grains under the crust. These melt forms will stay wet or moist in lower elevations until temperatures remain cold enough to freeze through the whole pack.
The past 3 days have brought 30cm in the valley and more at elevation along with strong winds in the Alpine and at tree line that has deposited greater amounts of snow on the East and South East lee slopes. There are now areas of wind slab and exposed rain crust; extreme spacial variation.
Travel advisory:
Take due care in avalanche terrain as new snow accumulates and stability decreases through wind transport and the creation of slabs. Watch out for unsupported steep cross loaded slopes and leading in from shallow snow areas where the wind slab will be more reactive and easier to trigger. Be aware that Cornices are once again growing and will be tender. Stay away from cornices all together. And remember to travel with partners in the backcountry.
Hazard:
Alpine: Considerable
TreeLine: Considerable
Below Tree Line: Considerable
January 19, 2010
Over the last 3 days the sun has been out in force and has done it’s duty in stabilizing the mountain snowpack. There are crusts due to the solar radiation on solar aspects but still very good snow at elevation on the North faces. No avalanche activity has been recorded in the last 2 days and is not expected with the present conditions. Snow tests today in the Tsugaike area have shown only Hard or moderate fractures with a resistant characteristic. This is very reassuring and has allowed for some great stable riding in the backcountry.
There is however talk of an overnight rain event starting in the evening of the 20th and turning to snow by the morning. This will definitely change the snowpack from the present good stability to a rapid decline in stability and may produce multiple surface avalanches due to water on the snowpack; especially at lower elevations. This rain is due to change to snow early the following morning (Jan. 21st) and thus things should freeze up and solidify once again. We may not see the rain at elevation and the new snow on the solar crusts may become reactive. Be ready for a mixed bag. Hopefully the rain is just a bad joke and temperatures will stay low enough to keep the precipitation as snow.
Until then all the best and watch out for cornice failure and low elevation loose avalanches due to rising temperatures.
Avalanche Hazard:
Alpine: Considerable
Tree Line: Moderate
Below Tree Line: Moderate
January 11, 2010
Synopsis:
The recent storm of 100110 came in from the North West in the middle of the night with little wind before winds shifted and came in from the South west with constant moderate force from 11:00 and strong gusts at all elevations through out the day. However at ridge top and in the Alpine winds were a more constant strong from the South West. Snow fall was between 2 and 3 cm per hour during the storm and by the end of the 18 hour storm 40 cm of dry new snow had accumulated in the Tsugaike area at 1700m. The new snow was accumulating on top of the previous days sun crust and evening surface hoar that had formed on south slopes, North and West slopes did not see the formation of the sun crust but tests on 110110 showed signs of buried surface hoar from the 090110 early evening pre snow fall in the early hours of 110110.
Avalanche Activity:
Evergreen Guide Trevor Carter reported slab avalanches running natural on the steep North aspect of Wakagurimine, Otari in the afternoon of 100110 during the hight of the storm. Today’s clear weather gave clear views of the skier triggered wind slab, size 2 on the East face of Norikura Dake. The crown fracture could be seen just below the cornice high up on the prominent East face just climber’s right of the summer trail. There has been a lot of stored energy and tension in the new snow due to rapid accumulation and intermittant moderate and strong winds and thus shooting cracks have also been observed both during and post storm. Debris from multiple size 2 loose naturals during the storm on the east faces of Yamakami no One were also observed today. Most of these stopped mid or bottom of track.
Tests:
Tests in the Tsugaike area during and post storm found the weakest layers at the new snow / crust or new snow / buried surface hoar interface down 15 ~ 25 cm on Southern and Northern aspects. ( CTE SC on / □ .5 ~ 2 mm ) The N aspect snow pack has multiple faceted layers with in the upper 50 cm in both the new snow and past storm snow. An AK block 3 SP released with in the old storm snow at 50 cm. ECT M at 40 cm from surface with 50% propagation was also observed in the same location on the North aspect of Hiyodori west saddle; 1900 m.a.s.l.
Travel Advisory:
Be extremely cautious in the Alpine with travel on lee slopes and cross loaded slopes in the Alpine not advised. There were continued strong winds at ridge top all day 110110 with moderate snow transport to the east facing slopes. Use caution on lee slopes and cross loaded slopes at Tree Line on steep and convex terrain. Be aware that there are definite wind slabs with stored tensile energy still waiting to release. Take due caution also around cornices as they are still fragile and getting bigger by the day.
Most treed areas below tree line have been quick to stabilize and are still good riding on the northern aspects. Do be careful of large tree wells and steep convex slopes, entering open glades and exiting on to cat road cut banks as there is still a possibility of rider triggered slabs in steep terrain.
Avalanche Hazard:
ALPINE: High with continued strong winds ( lee slope loading)
TREE LINE: Considerable ( lee slopes)
BELOW TREE LINE: Moderate (watch for day time warming and solar radiated slopes)
January 07, 2010
The season to date has seen a lot of snow fall in a relatively short time. This has meant that Hazard has been in the High and Extreme range often in the Alpine and Tree line zones over the last 3 weeks. But we have also seen a large amount of settlement in the snowpack over the same period. There are few layers of great concern deep in the pack (Below Tree Line) as mild temperatures and relatively light and calm winds have been predominant. The snow stability is NOT by any means good yet and as more snow is forecasted this week the stability will once again deteriorate. It has been great skiing and riding on the resorts and off piste Below Tree Line and there has been little need to ride outside of the ski resorts to get great turns. Continue to be cautious, play safe and always go with friends or a guide that know the area and understand the conditions at hand.
Present Conditions:
Surface instability. Facet / New Snow weak layer. Added weight with new snow may cause sluffs or slabs from this interface. Watch for wind increases and lee side loading.
The Heavy snow fall of 60 cms in the valley and more at elevation over the past 2 days (04/050110) put immediate excess weight on the underlaying layers and made for very unstable surface snow. This new storm snow was sluffing on any aspect on slopes of 30 degrees plus and was traveling good distances while gaining volume and speed. Early in the morning of 060110 the skies began to clear and the storm cycle passed to leave fair to poor stability at tree line and below and very poor stability (presumed; unobserved) stability in the Alpine. Due to the high density and high moisture content of the storm snow as well as warm day time temperatures there was rapid settlement in the new snow and subsequent bonding due to light winds and mild temperatures. Alpine unobserved but presumed to have greater slab formation due to rate of snowfall and associated winds at elevation. Last nights (060110) clearing allowed for further settlement and bonding. Radiant cooling has also lightened the storm snow (05/060110) surface and some surface hoar has been created. This low density surface snow combined with near surface faceting and hoar frost may produce a weak interface with the new snow falling today and continuing through to the weekend. Expect the avalanche hazard to rise with new snow and wind effect.