Flash Flood Guidance continues to show flooding potential into the weekend as additional rain is in the forecast. The ground is completely saturated due to this near record May for rainfall.
One reason for the increased flood threat is due to the very high "Precipitable Water" values across the area. Precipitable water (PWAT) is the depth of water in a column of the atmosphere, if all the water in that column were precipitated as rain. In other words, if the atmosphere has 2" of PWAT, any thunderstorm that develops will have the ability to drop 2" of rain within an hour. That may not sound like much, but two inches of rain falling on just 1 acre is roughly 54,308 gallons of water and weighs about 226 tons. That type of force and weight can cause flooding since it will overwhelm infrastructure.
The map above shows that the PWAT values over the weekend will still be high, keeping the flooding potential around Maryland. The goodnews is that the 7 Day Forecast is showing some drier and brighter days ahead as we move into June.