GOLDEN VALLEY, Minn. - For snow to fall, three atmospheric conditions are needed.
The first and the most important factor is temperature. Temperatures from the cloud down to the ground need to be at or near freezing so the snowflakes don't melt on their way down.
But it can still snow if surface temperatures are above 32 degrees as long as that layer of warmer air at the surface is less than 1,500-feet thick.
Temperatures within a cloud, which is called the "snow growth zone" need to be between 1 to 10 degrees for snow crystals to develop.
Secondly, and also in the snow growth zone, there needs to be enough moisture, generally a relative humidity of 70 percent or higher. That will lead to snowflake development.
And third, something needs to lift the moist air up so it can cool which allows water vapor to turn into snowflakes.
In many cases, the lift comes from a cold front that shovels in arctic air underneath the warmer air which was already in place.
In the case of northwest Minnesota, all three requirements were in place to really pile up the snow!
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