Friday March 8, 2019
Loose Wet, Loose Dry
Travel & Terrain Advice
Convective snowfall activity late Thursday makes for difficult prediction of new snow amounts and often results in great spacial variability in depths, so be sure to take note of how much new snow actually lies on top of the slightly firmer old snow from last week.
Take extra caution when playing on steep north facing slopes in the treeline and alpine especially if terrain traps exist below. Use ski/sled cuts and slough management to reduce your risk of being involved in loose dry avalanches.
With the arctic like winter coming to an end we need to start to readjust our mindset to typical island temps and spring snow pack behaviors. Temps have started to warm and will even get hotter in the days and weeks to come (esp as the spring sun becomes even more powerful). Start to think about loose wet avalanche activity and how to reduce exposure mid-day.
Still a good idea to avoid shallow spots in the snowpack at treeline and alpine where we may (though unlikely) trigger an avalanche on the facet crust combo that cause all that avalanche activity a couple weeks ago.
No new avalanche activity has been reported besides some small minor loose sloughing of surface snow on steep north facing shaded slopes up to size 1.
As we approach spring the suns affects on the snow pack get stronger and we are finally coming to an end of this arctic like winter season. With this general daytime warming we may see some loose wet avalanche activity in the small amount of new snow that fell Thursday. We may possibly see up to size 1 avalanches on steep solar affected south facing slopes at below treeline elevations.
New snow that feel in the east (only) late Thursday has fallen on a widespread weak layer of surface hoar crystals and even began to fall as graupel (snow equivalent of hail, weak and acts like ball bearings) so the new snow has a very likely to likely potential to slide easily. Luckily there is not very much new snow, so any loose dry avalanche activity will only up to size 1. We can expect to find loose dry sloughing activity on steep north aspects and any well shaded steep zones in the treeline and alpine.
Convective snow flurries late Thursday have brought some light amounts of new snow to the eastern part of the bulletin zone. Unfortunately the amount of new snow was no where near the maximum depths the weather forecasts predicted last Wednesday. We have approximately 5-9 cm in the east , 1 cm to a trace in the west and only 1 cm to a trace up north. Light winds have kept weak surface hoar crystals intact and they now lie under the new snow (where it fell) and will likely act as a sliding layer. Warm afternoon temps and cold nights have resulted in a thin melt freeze crust on steep treeline and below treeline SOLAR aspects. The old facet crust combo that resulted in a lot of avalanche activity a couple weeks ago has settled out for the most part and is not showing results in test.
|Surface||New snow ( where it fell in the east )over a suspected weak layer (surface hoar). Sun crust on solar facing slopes|
|Upper||Old storm snow well settled and bonding moderate to the facet crust below|
|Mid||Facet crust that is no longer producing in tests (down 20 to 50 cm approx)|
Convective snow fall late Thursday fell with light winds in the eastern part of the bulletin zone and covered over a widespread weak layer of surface hoar crystal. Temps were cold at night but did rise to near zero during the day, indicating the approach of spring diurnal cycles and a warming snow pack.
Very light to only trace amounts of snow are predicted for the next three days. Winds will be light and will only begin to rise to moderate later in the day Sunday. Temps will be cool (not freezing cold as they have been) overnight and will be warm and approaching zero during the day, esp as freezing levels begin to rise.
Friday - zero to 3 cm of new snow, winds light and from variable directions, temps -8 to -2, freezing levels 0 to 900 m.
Saturday - zero to 3 cm of new snow, winds light NW to SW, temps -7 to -1, freezing levels 0 to 1000 m.
Sunday - zero to a trace of new snow, winds light S rising to moderate S in the afternoon and to strong overnight (potentially ushering in the next snow storm for Monday). temps -6 to 0, Freezing levels 0 to 1000 m.
Posted on Friday March 8, 2019 by Bill Phipps