ROANOKE, Va. – It’s a combination that doesn’t sound right. A hurricane one minute, and snowflakes falling the next.
The weather world in our corner of the world started buzzing Friday evening with reports of snow and sleet mixing in with the rain associated with Ian.
Currently in heavy pings from sleet at Whitetop Mtn (5525’). Several large trees downed on Whitetop Rd. Winds gusting >50 now. Temps 36 and falling. #Ian #vawx @NWSBlacksburg @WSLS_Michaels @WCYB_DavidBoyd @VaDOTBristol @spann @JimCantore pic.twitter.com/EtcWMcwyhc— Billy Bowling (@babowling12) September 30, 2022
How did this happen?
Ian, once inland, went post-tropical. This indicates that it no longer had a warm center, but a cold center to it - like most inland storm systems do.
Once heavy rain began falling in the high country of North Carolina and in places like Whitetop, some other processes came into play.
When air rises, it expands and saturates. That’s the process that forms clouds and eventually precipitation.
In this atmospheric profile you see below, the air was rising rapidly in something known as a dendritic growth zone (DGZ).
That heavy precipitation then fell into a layer of very dry air, where it evaporated. Evaporation cools the air and, in some cases, cooled it enough to see snow and sleet.
I even had reports of something like snow falling in areas like Clover and Lynchburg. It more than likely was something known as graupel, when raindrops collect on melting snowflakes.
Graupel is soft to the touch, and it is often mistaken for snow or hail.