|LOCAL FREAKISH WX SERIES:|
3+ INCHES OF GRAUPEL IN AN HOUR
METEOROLOGIST JEFF HABY
The experience with graupel is that it is a combination of a large snowflake and a small hailstone. They fall faster than snowflakes
but a little slower than hail. Sometime graupel is called “soft hail”. It forms by large snowflakes that are suspended aloft that grow
by supercooled water drops freezing on the snow. This allows graupel to have a bright white color and a faster fall rate than snow. This
type of storm is more common in higher elevation regions since there is an absence or a significant reduction in the amount of warm
air the precipitation needs to falls through to reach the surface. In a lower elevation location, it is more likely the graupel
will melt into heavy rain before reaching the surface.
Relatively strong lifting is needed to form graupel, thus when it does form, many times a heavy shower of graupel will be experienced. Graupel
can accumulate on the ground in a similar fashion to heavy snow. Several inches can fall in an hour especially if the storm is slow
moving. It can look like several inches of snow occurred. Unlike snow though, it is not good for making snowballs and is denser
In a freak graupel storm, a convective storm will form in an environment that supports frozen precipitation that can reach the surface.
Heavy precipitation forms in the updraft. The strong updraft and cold temperatures allow for a heavy winter precipitation to
develop aloft. Instead of the heavy rain that a thunderstorm would have, heavy graupel falls to the surface. It can accumulate
quickly. In the bigger storms, snow plows will be needed to remove the accumulation from roadways.