A refresher on winter precipitation types
Whether you like it or not, winter is gradually making its presence known.
With winter weather sometimes comes confusion about the type of precipitation falling from the sky.
The two most common misunderstandings during winter weather are that it’s hailing and that it’s freezing rain when it isn’t.
Let’s start with hail – I received reports of hail falling in parts of Nova Scotia Wednesday afternoon.
The key to remember is that hail is formed within thunderstorms. So, unless we’re experiencing thundersnow that’s producing hail – which is quite rare — it’s not hail you’re seeing. It’s likely ice pellets or graupel.
Ice pellets form when snowflakes in the upper levels of the atmosphere start melting in a warmer layer or air below but refreeze once they enter a cooler layer and land at the surface.
Graupel, sometimes referred to as snow pellets and at times soft hail, forms when supercooled water droplets freeze onto snow crystals through a process called riming, then fall to the ground as tiny white snow pellets.
This leads me to my next point. People often think these frozen pellets are freezing rain, but it’s far from it.
Freezing rain occurs when snowflakes melt completely in a warmer layer of air. The droplet then enters colder air directly at the surface, supercooling it and allowing it to freeze on direct contact with surfaces.
The key to remember is that freezing rain is not frozen until it reaches the surface. Thus, it does not fall as a frozen water droplet and builds an ice accretion on surfaces.
These are just a few things to remember when reporting precipitation this winter season.