July 16, 2018 at 3:05 PM
In less than a month, Washington’s rainfall fortunes have switched from deluge to developing drought. From mid-May to mid-June, it rained incessantly. Now, we can hardly buy a drop.
For the first time in recorded history, no measurable rain fell in July’s first 15 days. Washington’s lack of rain dates to June 27, a streak of 18 consecutive days. The longest rainless streak on record in Washington is 34 days during September and October 2007, but it is not in serious jeopardy given rain in the forecast.
However, the current dry spell is packing a punch. As Capital Weather Gang’s Angela Fritz explained last week, it exhibits some characteristics of a flash drought, or one that begins abruptly, spurred by both heat and a lack of rain. (Note: There are varying definitions of a flash drought.)
Much of the immediate D.C. area has received less than 5 percent of its normal rainfall in the past two weeks. Even those lucky spots briefly doused by some spotty showers have tallied less than 25 percent of their normal rainfall. Most of the Eastern United States has witnessed such below-normal rainfall since the beginning of July.
Lawns and gardens that were previously lush and green are turning brown.
The recent dearth of rain stands in sharp contrast to circumstances in mid-May, when Washington received at least 0.4 inches of rain on a record seven straight days. In early June, thanks to another round of downpours, the Potomac River in Washington crested at its highest level since March 2010.
Adding together the rainfall and lack of rainfall over the past 60 days, the total comes out very close to normal.
The short-term rainfall deficit hasn’t yet built up enough for a drought to be declared by the federal government’s U.S. Drought Monitor. Whether it is will depend on how long rain continues to elude the region.
A cold front sweeping through the region Tuesday is likely to set off showers and storms, but rainfall will be highly variable. Then we’ll have several more dry days. Computer models have shown some potential for showers and storms at times this weekend, but they are inconsistent about their intensity and coverage.
The National Weather Service Climate Prediction Center is favoring above-normal precipitation next week across the region, possibly presenting an opportunity to break out of this dry pattern.