Spotty nature of precipitation right now

[WestWind]

Here is a current radar shot.  Look at how spotty the snow shower activity is, particularly over Indiana and Ohio.

 

What causes this?  I know wind can cause it, but I don't think there are any strong winds in the region presently.  Does it have something to do with the late-winter sun being stronger and able to create local updrafts better than earlier in the winter?

 

[csnavywx]

They're just daytime-instability driven snow showers in broad cyclonic flow. There's basically enough low level moisture around and very steep lapse rates (-40C at 500mb, -25C at 700mb!) to help kick them off. They should wind down now that the sun is down.

[IWXwx]

The lake helps to add a little moisture over areas with favorable fetch.

 

These cells can put down a surprising amount of snow over a small area in a short period of time. I drove up I 69 this morning with just a dusting on the ground, then suddenly hit a 3 mile stretch near FWA where a recent cell laid down an inch, then just as suddenly it was back to a dusting. A few miles north, I hit another short stretch where and inch + had occurred.

 

This was just after daylight, before the sun and wind could do its deed. Pretty neat to see.

[Powerball]

They're like summer time popcorn t'storms.

 

The reason the activity is spotty is because there's no notable trigger mechanism (or storm system) to produce large scale forcing. The "updrafts" depend solely on surface convergence to lift the moisture at the surface into the instability aloft.