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Wednesday March 22,2017

March 22, 2017 at 04:43AM

This Bulletin Valid Until: Friday March 24, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Wednesday Thursday Friday
Alpine CONSIDERABLE HIGH HIGH
Treeline CONSIDERABLE HIGH CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate

Main Concerns: (Avalanche problems)

Wind Slab-  Wind slabs will form in the alpine and at treeline during both Thursday and Friday. Up to 100 cm of new snow and rain at some elevations combined with moderate to strong south west and south east winds will promote the development of these hazardous avalanches. During storm events, wind slabs specific to lee aspects and will be touchy to very touch to triggers and large in size( size 2).

Persistent Slab-  Deep and stubborn. A melt freeze crust formed on all aspects and all elevations in mid February is buried down between 80 and 100 cm. In lee areas in the alpine this persistent weakness has been found down 172 cm in depth. Currently this weakness is stubborn to light surface triggering. When ideal conditions exist to produce enough load to awake this deep instability, it will produce large to very large avalanches (size 3).

Loose Wet New snow and rain at elevations below 1500 meter, will promote development of loose wet avalanches. Found on all aspects and at all elevations  tree line and below. Loose wet avalanches could be large in size and will be very touchy to human triggers during storm periods and when temperatures rise.

Travel/Terrain Advice: Dangerous avalanche conditions exist and travel in avalanche terrain is not recommended.

Past Weather: Moderate to strong south east and south west wind with up to 15 cm of new snow. 

Avalanche Summary:  A few small (size 1) loose avalanches reported all failing within the new snow on steep north and west aspects.

Snowpack Description The upper snow pack is settling well under current mild temperatures and precipitation.The mid March rain crust is prevalent on all aspects and elevations, up to 20 cm thick and buried down 20 cm under new dense well settled snow. The new snow is bonding moderately well with resistant planar results reported. The mid February persistent weakness can be found between 80 to 150 cm and possibly up to 200 cm in isolated lee terrain in the alpine. Above and below the layer facets are present and are a compounding factor of this instability.This layer is producing easy results when isolated and tested. The mid and lower snow pack are well settled and dense snow pack conditions are found. 

Surface- well settled new snow

Upper-  between 80 to 150 cm overlie a melt freeze crust

Mid-  Well settled.

Lower- Well settled.

Weather Forecast:  Unsettled spring weather continues,a series of weak disturbances will spin thru the forecast region bringing light to moderate snowfall and southwest and south east winds. Eastern zones will receive substantially less precipitation more sun effect and periods of clearing between storms, while western front ranges will receive the brunt of the storms with significantly higher precipitation amounts forecast. 

Wed -   up to 20 cm new snow    Winds SW to 40 km/hr.     Freezing level to 1500 m.

Thur-  up to 50 cm new snow      Winds SE to 50 km/hr.      Freezing level to 1100 m.

Fri-     up to 50 cm new snow       Winds SE to 60 km/hr.      Freezing level to 1200 m. 

 

Prepared by Jesse Percival

Monday March 20,2017

March 20, 2017 at 04:16AM

This Bulletin Valid Until: Wednesday March 22, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Monday Tuesday Wednesday
Alpine MODERATE MODERATE HIGH
Treeline MODERATE MODERATE CONSIDERABLE
Below Tree line LOW LOW MODERATE

Confidence: low, uncertainty with predicted precipitation amounts and limited upper alpine snow observations.

Main Concerns: (Avalanche problems)

Wind Slab-   Past light to moderate south east and south west wind has formed wind slab in the alpine and at tree line. Wind slabs can be found on lee aspects and located in features such as ridge top areas and steep convex rolls. Avalanches from wind slabs could be large (size 2) and have have been reported to be stubborn to ski cutting but may be touchy to triggers in isolated terrain features.

Persistent Slab-  This persistent weakness within the snow pack is bonding poorly in both the alpine and at treeline. A layer of low density facets overlie the crust and recent snow pack tests produced easy results at treeline. The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200 cm. Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain. 

Travel/Terrain Advice:  Evaluate snow and terrain carefully, seek to identify features and areas of concern. Be especially aware of increasing danger levels as precipitation amounts increase and temperatures and freezing levels rise. 

Past Weather: Up to 20 cm of snowfall and light to moderate south east and south west wind. Cool and clear conditions have formed surface hoar on all aspects. Daytime solar effect has moistened snow surfaces on solar aspects and overnight cooling formed a breakable surface crust.

Avalanche Summary:  No new natural avalanche activity reported in the past 72 hours. Avalanche control teams reported ski cuts produced only small (size 1) loose dry avalanches on steep north west aspect treeline terrain.

Snowpack Description: Clear and cold temperatures in the last 48 hours has created small surface hoar on all aspects and at all elevations.A variety of surface conditions exist and are dependent on elevation and aspect. Moist on solar aspects,pressed and dense on windward aspects, and low density snow on protected north facing aspects.The mid March layer is buried under low density snow down up to 20 cm and is bonding moderately. The mid February persistent weakness is bonding poorly but currently non reactive to heavy surface triggers.This lingering concern will produced very large avalanches when woke and will likely remain a concern for the remainder of the season.Beneath this the snow pack is well settled and dense.   

Surface: Surface hoar up to size 3mm

Upper-  100 to 150 cm overlie mid February melt freeze crust (persistent weakness)

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:  A brief period of high pressure will bring clear and cool conditions for the next 24 to 36 hours. A south westerly flow will follow and produce continued unsettled conditions bringing to the region moderate south west wind, rising freezing levels and temperatures. Snowfall amounts are expected to be moderate with the exception of western zones. Current forecast models predict that in western zones of the forecast region, snowfall amounts may exceed 50 cm.

Mon - trace amounts of snow   Winds E to  30 km/hr Freezing level 1200 m.

Tues- up to 20 cm of snow  Winds S to 50 km/hr Freezing level 1500 to 1600 m.

Wed- up to 50 cm of snow and some rain  Winds SW to 40 km/hr Freezing level 1500 down to 400 m. 

 

Prepared by Jesse Percival

Friday March 17,2017

March 17, 2017 at 05:30AM

This Bulletin Valid Until: Sunday March 19, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Friday Saturday Sunday
Alpine CONSIDERABLE CONSIDERABLE CONSIDERABLE
Treeline CONSIDERABLE CONSIDERABLE CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate: uncertainty in determining above 1800 meters in elevation the current upper snow pack conditions, specifically seeking the existence of the new melt freeze crust and its strength and bonding properties with new snow. The other uncertainty that resides above 1800 meters in elevation is the bonding properties, depth and distribution of the deep persistent crust. Seeking observations and information from public observers. If you have the training, experience and skill level to access alpine avalanche terrain , please forward your observations to forecaster@islandavalanchebulliten.com

Main Concerns: (Avalanche problems)

Wind Slab-   New snow between 10 to 25 cm is expected during this forecast period combined with moderate south east and south west wind will produce wind slabs. Wind slabs will be present in lee terrain and located in features such as ridge top areas and steep convex rolls. With the exception of elevations above 1800 meters wind slabs will be seated on a recently formed hard crust and will be very touchy to human triggers . Avalanches from wind slabs could be large (size 2 )in size and will become very touchy to all triggers when temperatures begin to warm.

Persistent Slab-  This persistent weakness within the snow pack is bonding moderately well at treeline and poorly in the alpine.The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200cm. Currently the new melt freeze crust is bridging the upper snow pack, providing this deeper crust with a protective layer from light to moderate loads.  Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain 

Travel/Terrain Advice:  Very dangerous avalanche conditions, travel in avalanche terrain is not recommended. If users intended to travel in avalanche terrain make conservative decisions, and utilize simple well support low angle terrain. Be especially aware of over head hazards (cornices) and avoid lee areas with deep pockets of fresh snow.

Past Weather:  Rain, warm air and moist surface conditions were followed with a sharp drop in freezing levels and temperatures promoting the development of a melt freeze crust. This very hard surface crust has formed on all aspects and elevations below 1800 meters and boots or skis will not penetrate it. Up to 15 cm of snowfall then fell on this new crust in the last 48 hours combined with moderate Se wind and cooling temperatures.

Avalanche Summary: 

  Tuesday March 14, warm and wet conditions produced numerous natural wet loose avalanches on North steep aspects at treeline and below treeline. These avalanches were large in size (size 2) and a couple of them gathered enough mass to put load on the persistent weak layer , causing a step down and producing slab avalanches between 40 and 60 cm deep.

Wednesday March 15, a few very large natural avalanches (size 3) were observed and reported.These avalanches were located at 1800 meters on north to north east aspects and had deep crowns, estimated at 1.5 to 2 meters. The avalanches failed on the mid February crust during the warming period, and initiated at the top of steep convex rolls, with unsupported terrain below.

Thursday March 16, Skiing cutting late in the day at treeline on a northwest aspect, produced small (size 1) wind slabs just below ridge top, being very touchy and running on the melt freeze crust, These avalanches did not have enough mass to run far

Snowpack Description: New low density snow of up to 15cm is bonding poorly to a very hard surface crust that formed on all aspects and elevations below 1800 meters. The hard crust has bridged the snow pack and boots or skis in most areas would not penetrate it.  Moderate south east and south west wind has transported this new snow to lee aspects. The persistent weakness can be found down 80 to 100cm and up to 200cm in lee areas in the alpine. Below is a well settled snow pack

Surface- new low density snow of up to 15cm overlie a well developed melt freeze crust approx 15cm in depth

Upper-   80 to 100cm overlie the persistent melt freeze crust

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:

 A westerly flow will continue to bring moderate south east and south west wind with moderate snowfall. Temperatures are expected to remain cool with freezing levels staying below 1000 meters for the duration of the forecast period

Friday -    up to 10 cm new snow   Winds SE to 30 km/hr Freezing level 700 to 900 m.

Saturday- up to 10 cm new snow  Winds SW to 25 km/hr Freezing level 700 to 900 m.

Sunday-  up to 5 cm new snow  Winds SW to 15 km/hr  Freezing level 0 to 900 m. 

 

Prepared by Jesse Percival

View older posts »

Wednesday March 22,2017

March 22, 2017 at 04:43AM

This Bulletin Valid Until: Friday March 24, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Wednesday Thursday Friday
Alpine CONSIDERABLE HIGH HIGH
Treeline CONSIDERABLE HIGH CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate

Main Concerns: (Avalanche problems)

Wind Slab-  Wind slabs will form in the alpine and at treeline during both Thursday and Friday. Up to 100 cm of new snow and rain at some elevations combined with moderate to strong south west and south east winds will promote the development of these hazardous avalanches. During storm events, wind slabs specific to lee aspects and will be touchy to very touch to triggers and large in size( size 2).

Persistent Slab-  Deep and stubborn. A melt freeze crust formed on all aspects and all elevations in mid February is buried down between 80 and 100 cm. In lee areas in the alpine this persistent weakness has been found down 172 cm in depth. Currently this weakness is stubborn to light surface triggering. When ideal conditions exist to produce enough load to awake this deep instability, it will produce large to very large avalanches (size 3).

Loose Wet New snow and rain at elevations below 1500 meter, will promote development of loose wet avalanches. Found on all aspects and at all elevations  tree line and below. Loose wet avalanches could be large in size and will be very touchy to human triggers during storm periods and when temperatures rise.

Travel/Terrain Advice: Dangerous avalanche conditions exist and travel in avalanche terrain is not recommended.

Past Weather: Moderate to strong south east and south west wind with up to 15 cm of new snow. 

Avalanche Summary:  A few small (size 1) loose avalanches reported all failing within the new snow on steep north and west aspects.

Snowpack Description The upper snow pack is settling well under current mild temperatures and precipitation.The mid March rain crust is prevalent on all aspects and elevations, up to 20 cm thick and buried down 20 cm under new dense well settled snow. The new snow is bonding moderately well with resistant planar results reported. The mid February persistent weakness can be found between 80 to 150 cm and possibly up to 200 cm in isolated lee terrain in the alpine. Above and below the layer facets are present and are a compounding factor of this instability.This layer is producing easy results when isolated and tested. The mid and lower snow pack are well settled and dense snow pack conditions are found. 

Surface- well settled new snow

Upper-  between 80 to 150 cm overlie a melt freeze crust

Mid-  Well settled.

Lower- Well settled.

Weather Forecast:  Unsettled spring weather continues,a series of weak disturbances will spin thru the forecast region bringing light to moderate snowfall and southwest and south east winds. Eastern zones will receive substantially less precipitation more sun effect and periods of clearing between storms, while western front ranges will receive the brunt of the storms with significantly higher precipitation amounts forecast. 

Wed -   up to 20 cm new snow    Winds SW to 40 km/hr.     Freezing level to 1500 m.

Thur-  up to 50 cm new snow      Winds SE to 50 km/hr.      Freezing level to 1100 m.

Fri-     up to 50 cm new snow       Winds SE to 60 km/hr.      Freezing level to 1200 m. 

 

Prepared by Jesse Percival

Monday March 20,2017

March 20, 2017 at 04:16AM

This Bulletin Valid Until: Wednesday March 22, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Monday Tuesday Wednesday
Alpine MODERATE MODERATE HIGH
Treeline MODERATE MODERATE CONSIDERABLE
Below Tree line LOW LOW MODERATE

Confidence: low, uncertainty with predicted precipitation amounts and limited upper alpine snow observations.

Main Concerns: (Avalanche problems)

Wind Slab-   Past light to moderate south east and south west wind has formed wind slab in the alpine and at tree line. Wind slabs can be found on lee aspects and located in features such as ridge top areas and steep convex rolls. Avalanches from wind slabs could be large (size 2) and have have been reported to be stubborn to ski cutting but may be touchy to triggers in isolated terrain features.

Persistent Slab-  This persistent weakness within the snow pack is bonding poorly in both the alpine and at treeline. A layer of low density facets overlie the crust and recent snow pack tests produced easy results at treeline. The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200 cm. Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain. 

Travel/Terrain Advice:  Evaluate snow and terrain carefully, seek to identify features and areas of concern. Be especially aware of increasing danger levels as precipitation amounts increase and temperatures and freezing levels rise. 

Past Weather: Up to 20 cm of snowfall and light to moderate south east and south west wind. Cool and clear conditions have formed surface hoar on all aspects. Daytime solar effect has moistened snow surfaces on solar aspects and overnight cooling formed a breakable surface crust.

Avalanche Summary:  No new natural avalanche activity reported in the past 72 hours. Avalanche control teams reported ski cuts produced only small (size 1) loose dry avalanches on steep north west aspect treeline terrain.

Snowpack Description: Clear and cold temperatures in the last 48 hours has created small surface hoar on all aspects and at all elevations.A variety of surface conditions exist and are dependent on elevation and aspect. Moist on solar aspects,pressed and dense on windward aspects, and low density snow on protected north facing aspects.The mid March layer is buried under low density snow down up to 20 cm and is bonding moderately. The mid February persistent weakness is bonding poorly but currently non reactive to heavy surface triggers.This lingering concern will produced very large avalanches when woke and will likely remain a concern for the remainder of the season.Beneath this the snow pack is well settled and dense.   

Surface: Surface hoar up to size 3mm

Upper-  100 to 150 cm overlie mid February melt freeze crust (persistent weakness)

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:  A brief period of high pressure will bring clear and cool conditions for the next 24 to 36 hours. A south westerly flow will follow and produce continued unsettled conditions bringing to the region moderate south west wind, rising freezing levels and temperatures. Snowfall amounts are expected to be moderate with the exception of western zones. Current forecast models predict that in western zones of the forecast region, snowfall amounts may exceed 50 cm.

Mon - trace amounts of snow   Winds E to  30 km/hr Freezing level 1200 m.

Tues- up to 20 cm of snow  Winds S to 50 km/hr Freezing level 1500 to 1600 m.

Wed- up to 50 cm of snow and some rain  Winds SW to 40 km/hr Freezing level 1500 down to 400 m. 

 

Prepared by Jesse Percival

Friday March 17,2017

March 17, 2017 at 05:30AM

This Bulletin Valid Until: Sunday March 19, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Friday Saturday Sunday
Alpine CONSIDERABLE CONSIDERABLE CONSIDERABLE
Treeline CONSIDERABLE CONSIDERABLE CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate: uncertainty in determining above 1800 meters in elevation the current upper snow pack conditions, specifically seeking the existence of the new melt freeze crust and its strength and bonding properties with new snow. The other uncertainty that resides above 1800 meters in elevation is the bonding properties, depth and distribution of the deep persistent crust. Seeking observations and information from public observers. If you have the training, experience and skill level to access alpine avalanche terrain , please forward your observations to forecaster@islandavalanchebulliten.com

Main Concerns: (Avalanche problems)

Wind Slab-   New snow between 10 to 25 cm is expected during this forecast period combined with moderate south east and south west wind will produce wind slabs. Wind slabs will be present in lee terrain and located in features such as ridge top areas and steep convex rolls. With the exception of elevations above 1800 meters wind slabs will be seated on a recently formed hard crust and will be very touchy to human triggers . Avalanches from wind slabs could be large (size 2 )in size and will become very touchy to all triggers when temperatures begin to warm.

Persistent Slab-  This persistent weakness within the snow pack is bonding moderately well at treeline and poorly in the alpine.The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200cm. Currently the new melt freeze crust is bridging the upper snow pack, providing this deeper crust with a protective layer from light to moderate loads.  Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain 

Travel/Terrain Advice:  Very dangerous avalanche conditions, travel in avalanche terrain is not recommended. If users intended to travel in avalanche terrain make conservative decisions, and utilize simple well support low angle terrain. Be especially aware of over head hazards (cornices) and avoid lee areas with deep pockets of fresh snow.

Past Weather:  Rain, warm air and moist surface conditions were followed with a sharp drop in freezing levels and temperatures promoting the development of a melt freeze crust. This very hard surface crust has formed on all aspects and elevations below 1800 meters and boots or skis will not penetrate it. Up to 15 cm of snowfall then fell on this new crust in the last 48 hours combined with moderate Se wind and cooling temperatures.

Avalanche Summary: 

  Tuesday March 14, warm and wet conditions produced numerous natural wet loose avalanches on North steep aspects at treeline and below treeline. These avalanches were large in size (size 2) and a couple of them gathered enough mass to put load on the persistent weak layer , causing a step down and producing slab avalanches between 40 and 60 cm deep.

Wednesday March 15, a few very large natural avalanches (size 3) were observed and reported.These avalanches were located at 1800 meters on north to north east aspects and had deep crowns, estimated at 1.5 to 2 meters. The avalanches failed on the mid February crust during the warming period, and initiated at the top of steep convex rolls, with unsupported terrain below.

Thursday March 16, Skiing cutting late in the day at treeline on a northwest aspect, produced small (size 1) wind slabs just below ridge top, being very touchy and running on the melt freeze crust, These avalanches did not have enough mass to run far

Snowpack Description: New low density snow of up to 15cm is bonding poorly to a very hard surface crust that formed on all aspects and elevations below 1800 meters. The hard crust has bridged the snow pack and boots or skis in most areas would not penetrate it.  Moderate south east and south west wind has transported this new snow to lee aspects. The persistent weakness can be found down 80 to 100cm and up to 200cm in lee areas in the alpine. Below is a well settled snow pack

Surface- new low density snow of up to 15cm overlie a well developed melt freeze crust approx 15cm in depth

Upper-   80 to 100cm overlie the persistent melt freeze crust

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:

 A westerly flow will continue to bring moderate south east and south west wind with moderate snowfall. Temperatures are expected to remain cool with freezing levels staying below 1000 meters for the duration of the forecast period

Friday -    up to 10 cm new snow   Winds SE to 30 km/hr Freezing level 700 to 900 m.

Saturday- up to 10 cm new snow  Winds SW to 25 km/hr Freezing level 700 to 900 m.

Sunday-  up to 5 cm new snow  Winds SW to 15 km/hr  Freezing level 0 to 900 m. 

 

Prepared by Jesse Percival

View older posts »

Wednesday March 22,2017

March 22, 2017 at 04:43AM

This Bulletin Valid Until: Friday March 24, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Wednesday Thursday Friday
Alpine CONSIDERABLE HIGH HIGH
Treeline CONSIDERABLE HIGH CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate

Main Concerns: (Avalanche problems)

Wind Slab-  Wind slabs will form in the alpine and at treeline during both Thursday and Friday. Up to 100 cm of new snow and rain at some elevations combined with moderate to strong south west and south east winds will promote the development of these hazardous avalanches. During storm events, wind slabs specific to lee aspects and will be touchy to very touch to triggers and large in size( size 2).

Persistent Slab-  Deep and stubborn. A melt freeze crust formed on all aspects and all elevations in mid February is buried down between 80 and 100 cm. In lee areas in the alpine this persistent weakness has been found down 172 cm in depth. Currently this weakness is stubborn to light surface triggering. When ideal conditions exist to produce enough load to awake this deep instability, it will produce large to very large avalanches (size 3).

Loose Wet New snow and rain at elevations below 1500 meter, will promote development of loose wet avalanches. Found on all aspects and at all elevations  tree line and below. Loose wet avalanches could be large in size and will be very touchy to human triggers during storm periods and when temperatures rise.

Travel/Terrain Advice: Dangerous avalanche conditions exist and travel in avalanche terrain is not recommended.

Past Weather: Moderate to strong south east and south west wind with up to 15 cm of new snow. 

Avalanche Summary:  A few small (size 1) loose avalanches reported all failing within the new snow on steep north and west aspects.

Snowpack Description The upper snow pack is settling well under current mild temperatures and precipitation.The mid March rain crust is prevalent on all aspects and elevations, up to 20 cm thick and buried down 20 cm under new dense well settled snow. The new snow is bonding moderately well with resistant planar results reported. The mid February persistent weakness can be found between 80 to 150 cm and possibly up to 200 cm in isolated lee terrain in the alpine. Above and below the layer facets are present and are a compounding factor of this instability.This layer is producing easy results when isolated and tested. The mid and lower snow pack are well settled and dense snow pack conditions are found. 

Surface- well settled new snow

Upper-  between 80 to 150 cm overlie a melt freeze crust

Mid-  Well settled.

Lower- Well settled.

Weather Forecast:  Unsettled spring weather continues,a series of weak disturbances will spin thru the forecast region bringing light to moderate snowfall and southwest and south east winds. Eastern zones will receive substantially less precipitation more sun effect and periods of clearing between storms, while western front ranges will receive the brunt of the storms with significantly higher precipitation amounts forecast. 

Wed -   up to 20 cm new snow    Winds SW to 40 km/hr.     Freezing level to 1500 m.

Thur-  up to 50 cm new snow      Winds SE to 50 km/hr.      Freezing level to 1100 m.

Fri-     up to 50 cm new snow       Winds SE to 60 km/hr.      Freezing level to 1200 m. 

 

Prepared by Jesse Percival

Monday March 20,2017

March 20, 2017 at 04:16AM

This Bulletin Valid Until: Wednesday March 22, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Monday Tuesday Wednesday
Alpine MODERATE MODERATE HIGH
Treeline MODERATE MODERATE CONSIDERABLE
Below Tree line LOW LOW MODERATE

Confidence: low, uncertainty with predicted precipitation amounts and limited upper alpine snow observations.

Main Concerns: (Avalanche problems)

Wind Slab-   Past light to moderate south east and south west wind has formed wind slab in the alpine and at tree line. Wind slabs can be found on lee aspects and located in features such as ridge top areas and steep convex rolls. Avalanches from wind slabs could be large (size 2) and have have been reported to be stubborn to ski cutting but may be touchy to triggers in isolated terrain features.

Persistent Slab-  This persistent weakness within the snow pack is bonding poorly in both the alpine and at treeline. A layer of low density facets overlie the crust and recent snow pack tests produced easy results at treeline. The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200 cm. Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain. 

Travel/Terrain Advice:  Evaluate snow and terrain carefully, seek to identify features and areas of concern. Be especially aware of increasing danger levels as precipitation amounts increase and temperatures and freezing levels rise. 

Past Weather: Up to 20 cm of snowfall and light to moderate south east and south west wind. Cool and clear conditions have formed surface hoar on all aspects. Daytime solar effect has moistened snow surfaces on solar aspects and overnight cooling formed a breakable surface crust.

Avalanche Summary:  No new natural avalanche activity reported in the past 72 hours. Avalanche control teams reported ski cuts produced only small (size 1) loose dry avalanches on steep north west aspect treeline terrain.

Snowpack Description: Clear and cold temperatures in the last 48 hours has created small surface hoar on all aspects and at all elevations.A variety of surface conditions exist and are dependent on elevation and aspect. Moist on solar aspects,pressed and dense on windward aspects, and low density snow on protected north facing aspects.The mid March layer is buried under low density snow down up to 20 cm and is bonding moderately. The mid February persistent weakness is bonding poorly but currently non reactive to heavy surface triggers.This lingering concern will produced very large avalanches when woke and will likely remain a concern for the remainder of the season.Beneath this the snow pack is well settled and dense.   

Surface: Surface hoar up to size 3mm

Upper-  100 to 150 cm overlie mid February melt freeze crust (persistent weakness)

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:  A brief period of high pressure will bring clear and cool conditions for the next 24 to 36 hours. A south westerly flow will follow and produce continued unsettled conditions bringing to the region moderate south west wind, rising freezing levels and temperatures. Snowfall amounts are expected to be moderate with the exception of western zones. Current forecast models predict that in western zones of the forecast region, snowfall amounts may exceed 50 cm.

Mon - trace amounts of snow   Winds E to  30 km/hr Freezing level 1200 m.

Tues- up to 20 cm of snow  Winds S to 50 km/hr Freezing level 1500 to 1600 m.

Wed- up to 50 cm of snow and some rain  Winds SW to 40 km/hr Freezing level 1500 down to 400 m. 

 

Prepared by Jesse Percival

Friday March 17,2017

March 17, 2017 at 05:30AM

This Bulletin Valid Until: Sunday March 19, 2017 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Friday Saturday Sunday
Alpine CONSIDERABLE CONSIDERABLE CONSIDERABLE
Treeline CONSIDERABLE CONSIDERABLE CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence: Moderate: uncertainty in determining above 1800 meters in elevation the current upper snow pack conditions, specifically seeking the existence of the new melt freeze crust and its strength and bonding properties with new snow. The other uncertainty that resides above 1800 meters in elevation is the bonding properties, depth and distribution of the deep persistent crust. Seeking observations and information from public observers. If you have the training, experience and skill level to access alpine avalanche terrain , please forward your observations to forecaster@islandavalanchebulliten.com

Main Concerns: (Avalanche problems)

Wind Slab-   New snow between 10 to 25 cm is expected during this forecast period combined with moderate south east and south west wind will produce wind slabs. Wind slabs will be present in lee terrain and located in features such as ridge top areas and steep convex rolls. With the exception of elevations above 1800 meters wind slabs will be seated on a recently formed hard crust and will be very touchy to human triggers . Avalanches from wind slabs could be large (size 2 )in size and will become very touchy to all triggers when temperatures begin to warm.

Persistent Slab-  This persistent weakness within the snow pack is bonding moderately well at treeline and poorly in the alpine.The weakness is located down between 80 and 100 cm. On lee aspects (North East and North West) the persistent weakness is suspected to be down 200cm. Currently the new melt freeze crust is bridging the upper snow pack, providing this deeper crust with a protective layer from light to moderate loads.  Further heavy loading and very warm temperatures may wake this deep instability and could produce very large avalanches in isolated terrain 

Travel/Terrain Advice:  Very dangerous avalanche conditions, travel in avalanche terrain is not recommended. If users intended to travel in avalanche terrain make conservative decisions, and utilize simple well support low angle terrain. Be especially aware of over head hazards (cornices) and avoid lee areas with deep pockets of fresh snow.

Past Weather:  Rain, warm air and moist surface conditions were followed with a sharp drop in freezing levels and temperatures promoting the development of a melt freeze crust. This very hard surface crust has formed on all aspects and elevations below 1800 meters and boots or skis will not penetrate it. Up to 15 cm of snowfall then fell on this new crust in the last 48 hours combined with moderate Se wind and cooling temperatures.

Avalanche Summary: 

  Tuesday March 14, warm and wet conditions produced numerous natural wet loose avalanches on North steep aspects at treeline and below treeline. These avalanches were large in size (size 2) and a couple of them gathered enough mass to put load on the persistent weak layer , causing a step down and producing slab avalanches between 40 and 60 cm deep.

Wednesday March 15, a few very large natural avalanches (size 3) were observed and reported.These avalanches were located at 1800 meters on north to north east aspects and had deep crowns, estimated at 1.5 to 2 meters. The avalanches failed on the mid February crust during the warming period, and initiated at the top of steep convex rolls, with unsupported terrain below.

Thursday March 16, Skiing cutting late in the day at treeline on a northwest aspect, produced small (size 1) wind slabs just below ridge top, being very touchy and running on the melt freeze crust, These avalanches did not have enough mass to run far

Snowpack Description: New low density snow of up to 15cm is bonding poorly to a very hard surface crust that formed on all aspects and elevations below 1800 meters. The hard crust has bridged the snow pack and boots or skis in most areas would not penetrate it.  Moderate south east and south west wind has transported this new snow to lee aspects. The persistent weakness can be found down 80 to 100cm and up to 200cm in lee areas in the alpine. Below is a well settled snow pack

Surface- new low density snow of up to 15cm overlie a well developed melt freeze crust approx 15cm in depth

Upper-   80 to 100cm overlie the persistent melt freeze crust

Mid-    Well settled.

Lower-Well settled.

Weather Forecast:

 A westerly flow will continue to bring moderate south east and south west wind with moderate snowfall. Temperatures are expected to remain cool with freezing levels staying below 1000 meters for the duration of the forecast period

Friday -    up to 10 cm new snow   Winds SE to 30 km/hr Freezing level 700 to 900 m.

Saturday- up to 10 cm new snow  Winds SW to 25 km/hr Freezing level 700 to 900 m.

Sunday-  up to 5 cm new snow  Winds SW to 15 km/hr  Freezing level 0 to 900 m. 

 

Prepared by Jesse Percival

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Important Notice

This bulletin covers the mountainous region of Vancouver Island from the Mt. Cain Ski Area in the North to the Beaufort range to the South including the mountains of Strathcona Provincial Park.

This is a regional forecast and significant variation may exist within the forecast area. The information and danger ratings are intended as a trip planning aid for recreational, backcountry users of avalanche terrain; they are not meant to be used as the sole factor in determining the avalanche danger presented by a specific slope.

Always include local weather, snowpack and avalanche observations in your decision to travel in avalanche terrain. Observations and experience may lead to different conclusions from what is reported or recommended. See disclaimer for further details. The technical data used to produce these bulletins is obtained from a variety of sources, including local ski areas and remote weather resources.