Something with I dont fully understand about evapouration and spring time snowpacks cooling at night,Can anyone explain.
What exactly happens for a frozen layer of snow to form on the snowpack overnight strong enough to skin on the next morning if the freezing level is well above that level during that said night.

Mark

I’d say it’s because the surface of the snow absorbs heat in the day and radiates it away at night. The efficiency of snow as heat radiator means that the snow surface can be a few degrees colder than the air temperature so on a clear night where it’s not quite a zero air temperature the snow surface will still cool to zero. Obviously the snow is at zero at ground level.

A potential problem occurs because this is creating a vapour-pressure contour in the snow pack which can metamorphose the layers it passes.

Always interesting to measure snow temps if you’ve got a thermometer, and (in up to the minute news) you can use a BCA snow thermometer to measure the temperature of jam if you happen to be making rhubarb & vanilla jam (this probably works with other jams)