Understand the ‘melt-freeze cycles’ and have fun with spring skiing!
Off-piste spring
skiing is one of the best things that the Northern French Alps has to offer.
With lift access to all slope orientations: north, east, south and west, you can
get on it with little effort.
Melt-freeze
Cycles
Once the new snow
melts during the day and then freezes at night (1 melt-freeze cycle) a few
times in succession after a snowfall, the top snow layer begins to form a crust
that gets deeper and stronger after each melt allows free water to drip down
and re-freeze during the night. Any given ‘melt-freeze’ layer becomes stronger
with each cycle of melting and freezing due to the deeper penetration of each
melt during the day, which then adds more depth to the potential frozen layer
at night. If untouched, the top of this frozen layer is smooth and solid first
thing in the morning, then it becomes progressively softer as the warm sun and
increased temperatures melt it as the day goes by. This process starts on east
faces because they get the sun first thing in the morning, then south, then
west (north faces at 2500 metres don’t normally get a melt freeze layer on them
until late April due to lack of sun).
For good
skiing!
The trick is,
after a couple of good melt-freeze cycles have created a solid layer on a
slope, you need to get on that slope when the snow surface is smooth and solid
with only 2 or 3 cm’s of soft melted snow on top (these are generally slopes
that have been in the direct sunlight only for an hour or so e.g. an East
facing slope at 9 or 10). Then you need to get off those slopes when the snow
surface begins to get too soft and mushy or you’ll start breaking through,
which is dangerous for your knees. AND the slope may be unstable due to all the
melting - then avalanches can be a problem.
In sum:
After a solid
melt-freeze layer has formed and there has been a good melt during the day, it
needs to freeze well the night before; the ideal is a cool clear night with
minimums of –2 degrees (or lower) at 2000 m. This will allow the melted parts
of the layer to freeze solid again from that altitude up. Then, in the morning,
you look to get on the east facing slopes first thing, 9 AM, because the sun
rises in the east and therefore those slopes get the sun first. Then you move
to south facing slopes, then west. Do this right and get some of the best
skiing of the season.
Aside from a
night that is not cool enough, the only thing that gets in the way of great
spring skiing is the nasty ruts in the snow that people leave behind because
they either ski spring snow slopes (slopes that get lots of sun in spring: E,S
and W) before the melt-freeze layer has formed or they ski the slopes too late
when they are too soft
and mushy.
Tip of the
week:
If you have any
questions about the timing of good spring skiing, just ask any off-piste guide
or instructor around town. They will be happy to explain because their quality
of skiing depends on people skiing it right!
Have Fun, Be
Safe!
Henry and the HAT
Team
See
http://www.henrysavalanchetalk.com
for the events this week!
Summary of the Past Week & Glance Ahead
I skied quite a bit with Dan Egan and his Ski Clinics groups last week here in Val d'Isère. So this week I asked him to do the snow report (I add in a couple hunches I have for the next few days at the bottom):
PLEASE remember that the snow is sitting on very firm and slick old snow that was frozen. So small pockets of activity are being reported from Chamonix to Val D Isere (several accidents have been reported). Watch out before you jump into a line of fresh snow - if you're good enough, cut the slope and, no matter what, pick an Island of Safety for an escape route. Just because there are tracks and your friends have skied doesn’t mean the slope won’t slide. Take responsibility for yourself and use precaution. As an old Val D Isere local once told me, Slowly, Slowly, don’t rush the mountain!
Be safe and have fun,
Dan Egan
Skiclinics.com
Posted by Henry Schniewind on 29 March 2009 at 11:22 in Avalanche accident comments, Chamonix current conditions, Henry's ski diary, News from HAT, Val d'Isere current conditions | Permalink | Comments (0) | TrackBack (0)