A vigorous low pressure system will move across the Ohio Valley region today, bringing soaking rains to an area that could use a drought buster. The low pressure early this morning was over the North Central Gulf coast (see picture below). This low was in perfect position just ahead of an upper level low, centered over Oklahoma, to allow rapid strengthening. At the time of the satellite image below, 1 AM EST, the lowest pressure over Louisiana was 1002 millibars, or 29.59" of mercury.
By the time the low crosses central Kentucky this afternoon, the pressure is forecast to drop to around 995 millibars, or 29.38" of mercury. To give some perspective, 29.38" was the lowest pressure recorded at Louisville back on Oct. 26th, when a line of strong to severe thunderstorms moved through southern Indiana and central Kentucky. Louisville was not at the center of this low however, as the lowest pressure recorded for that storm was well away from Louisville, over northern Minnesota, at 28.21" of mercury! As the low intensifies, it will pull up Gulf moisture, bringing several hours of light to moderate rainfall across the region (see current radar image below).
Many locations will see an inch of rain, with the best chance for higher totals forecast along the Ohio River Valley.
The Ohio Valley in central Kentucky and southern Indiana has the most need for rain, as that region is currently classified as under an extreme drought. The image below depicts departures from normal for rainfall over the past 90 days. The red color indicates locations that are 8 inches below normal for the past 90 days.
Behind the low pressure, expect winds this afternoon and evening to pick up quickly from the southwest and west. Wind gusts of 25 to 35 mph are likely by late afternoon across south central Kentucky and then across the rest of the region by evening.