Flood rain inundated District and its northern suburbs overnight
Evidence of a derecho climate change link, ten years after the 2012 storm
The zones between Silver Spring and Hyattsville and Rockville and Derwood, where up to 5 to 7 inches of rain fell, recorded the most rain. But much of southern Montgomery County, northern parts of the district and northern Prince George’s County saw at least 2 to 4 inches and fell over the course of several hours.
Next to the flood a severe thunderstorm that swept from the Potomac into Rockville between 7 p.m. and 7:30 p.m. Saturday fallen trees, including one on a houseevict residents.
There were nearly 17,000 power outages in Maryland as of Sunday morning as a result of the storms, including about 12,000 in Montgomery County.
In all, the National Weather Service received 31 reports of flooding from Saturday night through Sunday morning and 10 reports of wind damage, mostly from downed trees.
Here is a summary of the flood reports:
- The road connecting the Beltway and Clara Barton Parkway was closed due to flooding.
- Rock Creek Parkway, Potomac Parkway and Beach Drive in northwest Washington have been closed due to flooding. Numerous vehicles stranded in the flood water.
- A stream gauge on the northwestern branch of the Anacostia River shot up 6 feet in an hour near Hyattsville. A stream gauge just to the east in Brentwood recorded a rise of 7.2 feet in 50 minutes.
- A Hyattsville neighborhood near the intersection of 23rd Avenue and Sheridan Street was flooded by “several people trapped or displaced,” according to the Weather Service.
- Near Takoma Park, the east-west highway was closed at Riggs Road when Sligo Creek overflowed. A vehicle was stranded near the intersection of New Hampshire Avenue and Sligo Creek Parkway.
- Three vehicles were stranded just east of Silver Spring at Four Corners.
- Families have been displaced in Silver Spring over flooded basements and electrical hazards.
- In Chevy Case, Beach Drive was closed because Rock Creek overflowed between Connecticut Avenue and Kensington Parkway.
- Near Aspen Hill, part of MD-28 was closed due to overflowing water from Rock Creek, and water rescue was in place along Village Lane and Rippling Brook Drive.
Pete Piringer, spokesman for the Montgomery County Fire and Rescue, tweeted that emergency response teams responded to 449 incidents during the event.
Notably, very little rain fell in the south, while areas north of downtown Washington were flooded. Reagan National Airport increased just 0.53 inches, while Dulles Airport reported nothing measurable.
The torrential rain was triggered by a very slow moving front pushing south across the region. The Weather Service issued a flood warning in advance, citing the possibility of several inches of rain. In some areas, however, the amounts exceeded forecasts.
It initially appeared that the region could avoid the worst in the late afternoon and early evening hours on Saturday, when the onset of rain was originally forecast. Much of the storm activity was concentrated northwest of the area — near Frederick, Md., and to the west.
Summer in America is getting hotter, longer and more dangerous
But as the front slumped south after about 7 p.m., storms began breaking out in Montgomery County, sweeping repeatedly from west to east over the same areas, a phenomenon known as training.
1210a: Extremely heavy rain from McLean to Silver Spring to Laurel…several stranded cars and water rescues in Montgomery County tonight. Stay at home and do not try to cross a flooded street with your car. Avoid routes near creeks/streams. pic.twitter.com/hZWLrsGaAE
— Capital Weather Gang (@capitalweather) July 3, 2022
The storms could tap into enormous amounts of moisture. It had been a hot, muggy summer day, and rainfall, a measure of moisture content from high in the sky to the ground, was excessive.
The high-resolution NAM model simulated precipitation capable water levels between 2 and 2.5 inches over the region – in record territory for early July.
In a special bulletin issued at 11:24 p.m. Saturday, the weather service wrote that precipitation rates “could be as high as 2.5 inches/hour.”
A few other factors added to the storminess. The Weather Service Bulletin mentioned the approaching “shortwave energy” from the Ohio Valley, which helped weather the storms late into the night. The storms also fed each other. When a group of storms passed, their cool exhaust or outflow would help destabilize the atmosphere for more storms.
Finally, precipitation was likely increased by human-caused climate change. There is a well-documented increase in the intensity of the most extreme heavy rain events in the eastern United States, fueled by an atmosphere that is becoming warmer and wetter.
Climate change has increased humidity in DC, making it feel even hotter
This extreme rainfall event follows several others in recent years, including two historic floods in Ellicott City, Md., in 2016 and 2018 and one of the most extraordinary downpours since records began in Washington in July 2019, when it fell in just an hour 3.44 inches rained .
Such events are likely to become more frequent and intense in the coming decades as temperatures continue to rise.
https://www.washingtonpost.com/weather/2022/07/03/flooding-maryland-dc-silver-spring/ Flood rain inundated District and its northern suburbs overnight