The Washington Post
Hit-or-miss summer rains leave some areas parched — and they may get drier
Right around the District and especially its suburbs immediately to the north, rainfall has been abundant this summer, with numerous downpours and even some flash floods. Those living in this waterlogged urban zone might find it hard to believe that there are considerable parts of the surrounding area where the landscape is turning brown due to a notable lack of summer rainfall.
At Reagan National Airport — where the city’s observations are recorded — 12.99 inches have fallen since June 1, 1.31 inches above normal for the summer. But just 30 miles to the north, Damascus, Md., in northern Montgomery County has seen its driest summer in 49 years of records.
The rainfall disparities are a reflection of the hit-or-miss nature of summer downpours. During the colder months of the year, precipitation is more evenly distributed. But precipitation during the summer is much more random.
Damascus has seen only 6.7 inches of rain since June 1, which is less than the next-driest summer total of 7.17 inches, wrote Robert Leffler, a retired National Weather Service climatologist, in an email. He said the record-low summer total is roughly half of the recent average.
Even in the areas that have seen above-normal rainfall for the summer, precipitation has been declining over the past several weeks. An analysis of rainfall since Aug. 14 reveals that most of the area has seen belownormal amounts, with spotty exceptions in northeast Maryland and Central Virginia because of pop-up storms.
Despite the recent rainfall deficits, drought or even abnormally dry conditions do not yet appear close to the area in the U.S. government’s Drought Monitor. Only coastal areas of Maryland are teetering near drought in its analysis.
However, the drought in the Northeast has been creeping west and southwest.
While not explicitly shown in the Drought Monitor, Leffler believes a drought has commenced in some of Washington’s northern suburbs.
“The most intense area of drought is centered in northern Montgomery and Frederick Counties, Md., with a very strong gradient seen to very wet areas in close-by D.C.,” Leffler wrote. “[ The] area is about 75 miles long and 20 miles wide (1,500 square miles) and shaped like a torpedo.”
The dry conditions could expand, given the forecast.
No rain is forecast through Saturday, and then just a small chance of late-day showers and storms returns Sunday into early next week. Generally, high pressure is predicted to dominate, which limits cloud cover and rain chances.
Longer term, the outlook for rain is less clear. September and October are Washington’s fourthand fifth-wettest months on average.
But the La Niña pattern now in place historically favors near to slightly below-normal precipitation between September and November, according to Matt Rogers, founder of the Commodity Weather Group and Capital Weather Gang contributor.
The Weather Service’s Climate Prediction Center is generally forecasting drier-than-normal conditions over the next several weeks, which is supported by the European modeling system forecast.
A substantial portion of earlyfall precipitation in the region often comes from tropical systems and their remnants, and they are difficult to predict ahead of time. At the moment, there are no tropical systems threatening the United States.
While many indicators lean toward a dry forecast, “all it would take is some tropical remnants [later in the fall] to mess up the numbers,” Rogers wrote in an email.
An overwhelmingly dry fall would place a much greater portion of the region in a drought situation, which would only become an issue for local water resources if the winter and spring continued to be dry. There is little confidence in predicting precipitation that far into the future.