Do April Showers Cause Flooding?

The Potomac River

Although yesterday was the warmest day so far in 2015 in the Nation’s Capital (84 degrees), April can also feature inclement weather.  In fact, yesterday was the fourth anniversary of some severe flooding in Georgetown.  During the spring, the combination of snowmelt west of town and appreciable rainfall can sometimes combine to create localized flooding.  Such was the case in April 2011.

It’s quite common for rivers and streams to run a little higher during the spring as the Appalachian Mountain snowpack gradually melts west of the Nation’s Capital.  When heavy rain and thunderstorms add to the volume of water, than the water levels invariably rise in area streams and creeks.  On April 16, 2011, there was a severe weather outbreak in the Mid-Atlantic Region, with four confirmed tornadoes in Maryland and northern Virginia.  Fortunately, they were weak tornadoes and caused only minor damage.  However, the thunderstorms also brought appreciable rainfall with more than half an inch falling in the Nation’s Capital and more than that north and west of downtown. 

The heavy rainfall north and west of town took a day to flow into the Potomac River and travel downstream before it reached the banks of Georgetown.  The National Weather Service reported that the Potomac River rose above flood stage in places just west of Georgetown, such as Little Falls, where the river reached a crest of 11.9 feet – almost two feet above the flood stage of 10 feet.  The Potomac River crested at 22.5 feet at Harper’s Ferry, which was above the 16 foot flood stage. 

Since Georgetown is right on the water, occasional flooding is expected and safeguards are in place.  The Georgetown Harborfront, for example, is a popular spot for boaters to dock their boats so they could dine al fresco along the quay.  However, the protective wall wasn’t in place four years ago and some flooding resulted.  All the damage was repaired and the lessons were learned, so such an event shouldn’t happen again.

Over four inches of rain fell at National Airport during the last week of April 2014 and no significant flooding occurred downtown.  That helps illustrate the importance of proper preparation and timely forecasts.  A significant amount of rain is on tap tonight and tomorrow across the Mid-Atlantic Region.  The potential also exists for some intense thunderstorms tomorrow afternoon with the Storm Prediction Center calling for a “slight risk” of severe weather in the DC Metro Region.  So it’s important to listen to your favorite meteorologists for the latest forecasts so you can take steps to ensure your safety.  My colleagues on the WUSA9 weather team are an example of a good place to turn for the latest weather forecasts in the Nation’s Capital.