Uh, Oh

This looks like it may be very serious.

Here is the National Weather Service’s latest rainfall amount forecast valid from 8pm EDT this evening through 8pm EDT Wednesday. Note the 10″ amounts near Asheville.

This would be bad enough. But, the new ECMWF model, from AccuWeather, shows an even larger area of ≥5″ amounts in the Appalachians than the latest NWS forecast.

From AccuWeather. The maroon swath off the coast is predicted
heavy rain from Katia which is not currently forecast to move inland.
However, very high surf and rip currents may occur on the East Coast. 

In “average” soil conditions, this would be a recipe for massive flooding. And, it still may be. However, unlike NY and New England before Irene, soil conditions prior to the arrival of Lee are drier than normal where the heaviest rains are currently predicted to fall. The graphic below shows dry conditions (yellow and red) versus the very wet conditions (blues and purples) from the path of Irene.

The excessive rainfall forecast by the ECMWF is due to two low pressure systems interacting with each other. If this turns out to be correct, the geographic area forecast to have 5″ or more may be too conservative.

Regardless, if the 8-10 inches forecast by the NWS materializes, there will be serious flooding in those areas regardless of soil conditions. As to the rest of the area, we will have to wait a little longer to pin it down.

Given these forecasts, it is not too soon to be making preliminary preparations.  

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