The arctic front has cleared most of the region, if it hasn’t it will over the next hour or so. Temperatures will rapidly decline over the rest of the afternoon and early evening and the winds will increase with time. As those temperatures fall, there will be an increased snow:liquid ratio. If you remember the last two events had wet snow with them with typical 10:1 which simply means, for ever 1 inch of rain that falls you will get 10 inches of snow. The colder the atmosphere is, the drier the snow, the easier it is to accumulate. We are expecting the “fluffy” snow for this event due to the arctic air moving in. In terms of timing, I think this will be a bigger factor to the North across Central and Northern Indiana. But It will squeeze out an inch maybe up to 2 inches across the Northern tier of the Tri-State, generally north of I-64.

 

Just a little current analysis: Front has passed and we have a cold air mass moving in via a potent shortwave trough (Indicated by the color fill) That is what we call positive vorticity advection. This is a clockwise spin in the atmosphere measured at 500mb, or 17,000 ft in the air, that aids lift mainly to the east. To measure that lift, I also plotted the 700 mb(~9,000 ft up) Omega values. Negative Omega means air is rising, the lower that value the stronger the lift thus precipitation. Conversely, the positive values mean air is sinking. Things will quickly stabilize as this feature moves over head and it will. Its coming NE towards that Tri-State. Unfortunately I will be at work. I will not be available to do much in the way of nowcast. Either way, wheels are turning for this event. It won’t amount too much down here in the Tri-State, but we’ll take it! Generally 1-2 inches expected here. And 2-4 inches across most of Central Indiana and 3-6″ across Northern Indiana especially in Lake Effect zones.

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