I may have missed someone from responding to this about MESOSCALE DISK so will apologize if this is duplication.
I had never actually noticed one of these being placed by the Storm Prediction Center in our area before on APRS but certainly an interesting addition to the notification system for potential of severe weather in a specific area. I just now looked and there are over 100 in effect currently on APRS by the SPC and fortunately, none in NE Kansas! I'll pay a little closer attention from now on.
"The Storm Prediction Center (SPC) issues Mesoscale Discussions (MCDs) to provide guidance on hazardous weather events that are expected or currently occurring. These discussions can be issued anywhere from 30 minutes to several hours before a weather watch is issued. MCDs can cover a range of events, including:
Severe weather
MCDs can be issued when conditions are developing for severe weather, such as heavy rainfall, convective trends, and other phenomena
Hazardous winter weather
MCDs can be issued for hazardous winter weather events, such as blizzards, freezing rain, and locally heavy snow"
Bruce, WCØAA "I can use a phone to call a friend but, I can use Amateur Radio to make a new friend"