Afternoon Flood Threat Update

As most of you are well aware, we are already being subject to significant rainfall from the remnants of Tropical Storm Cindy this afternoon. Rain moved in early this morning, and has since given us a brief break. More showers should be moving through the region over the next hour and into the evening. Multiple areas of southern KY have already seen over an inch of rainfall.

Since the morning blog post was written, a few things have changed. One, the National Weather Service in Louisville has issued a Flash Flood Watch for southern Kentucky from 10 am Friday morning until 7 am Saturday morning.

This is in anticipation of significant rainfall from Cindy’s remnants. Cindy has become a remnant cyclone, but her influence is soon to be felt even more so that it is now. The system is associated with very deep, tropical moisture that has already set records. At Nashville, the Precipitable water value on this morning’s sounding broke the daily record by 0.03″, and at Shreveport, near Cindy’s landfall, crushed the record by 0.24″.

That is the same airmass that will be approaching us tomorrow afternoon, likely accompanied with extremely heavy precipitation. The morning models present plenty to be concerned with, but they mainly take the heaviest precipitation just to the north of Bowling Green as Cindy’s remnant low tracks directly over the region. This is a scenario painted by several models.

This has been a bit of a trend amongst the models – both hi-res and larger scale models alike – to keep a band of heavier precip just to the north of BG. This would place areas like Butler, Edmonson and northern Barren counties at greater risk for dangerous precipitation. That isn’t to say that BG is out of the threat by any stretch. The WPC and NWS Louisville think the higher precipitation will be centered across BG and just south.

The discrepancy is largely in timing and speed of the cold front. The quicker it approaches, the further south that heavy rainfall band goes. That bad is forecast to form in large part because of the frontal forcing and upper level divergence that will be present a top of it. If the cold front moves a bit fast than the models prog it to, then that band of heavy rainfall can shift southward.

If you are in that band, extreme precipitation is likely. The models are showing much of the 3-6″ of rain expected occurring during an 8-12 hour window, which will mean significant flash flooding would be possible. Additionally, with such extreme amounts of moisture in the atmosphere, locally higher amounts can’t be ruled out. Here is how the hi-res NAM model sees this panning out.

This is a dangerous situation; be sure to be aware of the areas that are commonly prone to flash flooding and avoid them. Never drive through a flooded roadway, either.

On the flip side, a more northern track of this band of rain would mean that the areas to the south of this would see a bit of clearing. Because of an approaching shortwave, Cindy becoming a shortwave and upper level divergence, this area may be favored for discrete shower/storm development tomorrow afternoon. An increase in atmospheric shear is forecast to accompany this, leading to a severe weather threat tomorrow.

Tornadoes and damaging winds are the highest threats from this portion of the system. Continue to keep up with the latest information here on the website, on Twitter (@wxornotBG) and on Facebook (Landon Hampton)! This is a fluid and serious forecast, and we will do our best to bring the latest information to you as the forecast unfolds.