** Flash Flood Watch for entire area until Saturday at 2 p.m. **
11:10 p.m. update: A flash flood warning has been issued for parts of Montgomery, Howard, Frederick and Loudoun counties into the early morning. Very heavy rain is impacting that region and much of the area as we head toward midnight. Additional flash flooding is likely. Turn around if you come across water on the road, or better yet stay home for the rest of the night.
10:10 p.m. update: While there was a brief break in the rain this evening, it has filled back in over the region as we head into the overnight. Moderate to heavy rain falling more often than not should be the story from here through the sunrise period or so. Some additional breaks become more likely around then.
MRMS Estimate as of 8pm pic.twitter.com/ZDz3AbAVMJ
— TerpWeather (@TerpWeather) July 29, 2017
When it comes to the airports, totals have a big range. The leader through 10 p.m. is National, with 2.43 inches of rain. That’s closing in on the record for the date of 2.90 inches, and it’s the wettest day in over two years for the city. At Dulles, “only” 0.84 inches has fallen, which highlights a story of lower totals out west so far. Up at BWI, 1.46 inches has been recorded. We haven’t seen an update on other totals since early evening, but even at that point some spots were in the 3 to 5 inch range.
From earlier…
We’ve got a rare and potentially dangerous heavy rain event developing over the region tonight. While some spots in the northern D.C. suburbs were drenched with anywhere from two to four inches of rain this morning, the main storm and associated energy is just beginning to approach our area. For most of us, the bulk of the heavy rainfall will occur from now through Saturday morning. It is during this period when most of the flood-related hazards will occur. And as always, you can get the latest warning information on Twitter from DC Weather Alerts and from the NWS D.C. office.
Through Tonight: Showers and thunderstorms will continue to increase in coverage this evening. Rain will be steadily falling through the overnight period, with several bursts of heavy or torrential rain and thunder embedded within the main rain shield. Rainfall rates could approach half an inch per hour in some of the heavier pockets. Flash flooding remains a high concern, especially in areas (Montgomery County) that received heavy rain this morning. Lows will be around 70 degrees with a north/northeast wind. Rainfall totals will range from one to four inches overnight, with localized higher amounts.
Tourists walk near the U.S. Capitol building during a heavy rain July 28, 2017, in Washington, D.C. (Photo by Oliver Contreras for The Washington Post)
View the current weather conditions at The Washington Post.
Tomorrow (Saturday): The heaviest rain should begin to rotate east of the District by Saturday morning. Nevertheless, light rain will persist for the much of the day as temperatures won’t make it out of the 70s. Winds from the north/northeast could become gusty in the afternoon at 10-20+ mph. Some scattered thunderstorms with bursts of heavy rain will develop in the late afternoon. Flash flood criteria will be easily met in any location where additional rain falls. Expect some drying out to begin Saturday evening, with just scattered showers remaining by the night. Low temperatures will settle in the low to mid-60s with a gusty north wind at 10-15 mph.
Sunday: Some clouds in the morning give way to bright sunshine by the afternoon. After all of the rain, Sunday will feel especially nice under mostly sunny skies. Temperatures will range from 78 to 83 degrees with little to no humidity to speak of.
See A Camden Walker’s forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter and Instagram. For related traffic news, check out Dr. Gridlock.
Lessons from Ellicott City: Sunday will mark the first anniversary of the Ellicott City flash flood event. Given our current weather situation, it appears that coincidence is not lost on Mother Nature. That said, make sure you stay safe, cautious and aware this weekend and adhere to the sound flash flood advice that the NWS provides. Too often, an event such as the one currently unfolding is not held in the same regard as a snowstorm or hurricane. But extreme rainfall and flash floods are just as, if not more, threatening. You need not look any further than July 30, 2016, for evidence of that fact.
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Ian Livingston contributed to this post.
