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.
Well, kind of, temporarily at least… Finally there is a light at the end of the tunnel as the overall pattern will shift after nearly a week of being stagnate with a stationary front over the region. In this case, some of that light for some will be lightning! But once we get this cold front by we can look forward to a much more tranquil end to this week! And trust me – I am all about storms etc. But it is welcome! Anyways below is your latest Nowcast covers this afternoon and early evening.
Severe Weather Update:
We have seen rain off and on over the past several days as a quasi-stationary boundary continues to meander across the Tri-State. Later today and this evening it is expected to move to the north of the Tri-State. Now normally that would be a good thing – however. In this case that only elevates the situation. Now not only are we getting more rain, but the threat of severe weather increases as we will now be placed in the “warm sector”. Moreover, there will be a stark 60 -70 kt low level jet that punches into the region ahead of a stronger mid-level shortwave as it sweeps across Illinois to the northwest of the Tri-State. That will drive instability and even more moisture that could/will enhance a isentropic shower/thunderstorm regime over the entire Tri-State. This is a BIG problem considering most if not all of the Tri-State has seen over 4 inches of rain over the past 3 days. If it hasn’t flash flood in your location yet – it will with the severe thunderstorms. Below is a video analysis of the situation… Best advice is to be prepared for the worse or to move to higher ground immediately. Also, to take shelter if there becomes a tornado threat, which is in play tonight…
Flood/Severe Weather Update 1
Flood/Severe Weather Update 2
We’re starting to sound like a broken record player here… There is a SLIGHT risk of Severe Thunderstorms for Friday for the entire Tri-State and much of Indiana… I’ll warn folks now. This is not the only system we’ll be tracking over the next seven days or so. Lets get to it.
There is a SLIGHT Risk for the Entire Tri-State
Threat of SEVERE Hail 2″ or larger is SIGNIFICANT (yellow) 30% chances within 25 miles of a point…