Thursday,March 19, 2020

Flash flooding likely: severe storms iffy

A fairly strong upper air disturbance will come across the lower Ohio Valley tonight.  Lucky for us, it’s focused mostly on Indiana.  With this upper system, we’ll see two clusters of thunderstorms overnight.  With the rains of the past two days, periods of heavy rain, especially over southern IN, will pretty much guarantee widespread pockets of flash flooding over northern KY and southern IN.  If you live in a flash flood-prone area, you know the drill.

The first cluster of thunderstorms will be over the area this evening.  The southern side is weak and will provide plenty of rain to west and central KY and initiate some of the expected flash flooding.  But no severe thunderstorms.

The first cluster of storms will be more noteworthy over the southern half of Indiana.  Severe storms are moving over southern Illinois and will race eastnortheastward.  Heavy downpours are likely and a few severe storms will be possible between, roughly, 8 P.M. and Midnight.  Primary threat will be strong winds and possibly some hail.

The second cluster of storms will move through the area between about 2 A.M. and 8 A.M.  This one is much stronger and is likely to produce an outbreak of severe storms from Arkansas, southeast Missouri and southern IL this evening.  By the time this cluster arrives in the Louisville region, it is likely to be weakening.  Plus, atmospheric instability will be diminishing. Also, the strongest dynamics will remain north of our area.

The result will be a very noisy night north of the Ohio River.  Flash flooding will probably become  a serious problem.  Storms will be strong, but probably not severe.  Along and south of the Ohio River, the primary line of thunderstorms most likely won’t arrive in Louisville until 5 A.M. or later.  They will not be very strong, but deposit enough rain to make a very messy rush hour before the exit the area by 8 A.M.