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Flood warnings in light green and flash flood watch in dark green (National Weather Service) Flood warnings in light green and flash flood watch in dark green (National Weather Service)

Overview: A deep plume of tropical moisture from the Gulf of Mexico is surging up the East Coast with a stream of moderate to very heavy rain.  Flood warnings and flash flood warnings are in effect through this afternoon and evening.  Two to five inches of rain have fallen from this storm system already, and another inch or so is possible through tonight.  Streams are overflowing their banks and flooding is also possible in low lying and urban areas.

Radar & lightning: Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Storm total rainfall is likely to reach 2.5-6 inches by Thursday morning, with locally heavier amounts possible. In addition to the flooding, there is a slight risk of severe thunderstorms that could produce damaging winds, hail, and a few tornadoes, especially in the southern part of the region. The most likely timeframe for possible severe storms is 6-11 p.m.

Along the Tidal Potomac and Chesapeake Bay, coastal flood warnings and advisories are in effect as southerly flow pushes tidal levels about one and a half to two feet above normal.    In the District (at Washington Channel in Georgetown), high tide is at 10:04 p.m. tonight.

4:45 p.m.: A severe thunderstorm and tornado warning is in effect for parts of Southern Maryland (Charles, Calvert and St. Mary’s County).  Our post on the severe weather threat this evening has the latest. See: Risk of severe weather, tornadoes focused south and east of Washington this evening

This is our last update in this post. We expect additional heavy rain and possible thunderstorms this evening, and more flooding is possible. For the latest, see our PM Update: Flood warnings through this evening, outside chance of severe storms; nicer Thursday

4:05 p.m.: Doppler radar shows widespread 2-5 inch rainfall totals across the metro region (and it’s not over).  The heaviest amounts are focused west and north of the District, with the bulls-eye in northeast Montgomery and central Howard counties.

Doppler radar estimate of total rainfall, click to enlarge (Courtesy Jordan Tessler, @TerpWeather)

Even though the rain has diminished west of I-95, standing water is still a problem for the late afternoon commute.  The next surge of rain arrives between 5 and 6 p.m.

This is dangerous…

3:45 p.m.: Radar shows the rain train has shifted just east of I-95, giving areas along and west of I-95 in the metro region a much-needed lull in the precipitation. I’m not convinced it will last long as more heavy storms are developing in central Virginia which could streak back into the region after 5 p.m.

Areas east of I-95 look to get hammered by training showers and storms (i.e. rain that tracks over the same areas repeatedly) for the next couple of hours.  1-2 inches of rain could fall in a short time and a flash flood warning is in effect for southeast Montgomery, northern Prince George’s, western Anne Arundel, and southeast Howard counties through 6 p.m.

3:30 p.m.: Flooding is ongoing and we have a report of yet another high water rescue, this time in Chevy Chase, Md. on the I-495 underpass at 9550 Cedar Lane.  TURN AROUND, DON’T DROWN.

Additional reports, via Twitter:

3:20 p.m.: We have a fresh update on the risk of severe thunderstorms and tornadoes this evening in this post: Risk of severe weather, tornadoes focused south and east of Washington this evening

2:40 p.m. There have been multiple reports of high water rescues today so let this be one additional reminder that it is extremely unsafe to attempt to driving across flooded roads.  You endanger yourself and first responders.  When you encounter high water on a road, turn around and find another way to your destination.

2:25 p.m.: Several locations have now picked up over 4 inches of rain from this event.  The National Weather Service reports 4.14″ in Gaithersburg and 4.5″ in Sterling.  Dulles Airport has received 4.18″, and 2.85″ today alone,  a daily record, and just 0.05″ off its wettest April day on record, 2.9 from April 20, 2008.  Reagan National Airport has also set a daily rainfall record, with 1.52″ so far (previous record 1.16″ from 2005).

2:05 p.m.: How much rain is falling today across the eastern U.S.? USA Today reportsAbout 2 trillion gallons of water will fall today in the eastern USA, according to an estimate from the U.S. Geological Survey. That’s figuring roughly 3 inches of rain across 370,000 square miles, which is about the area of the eastern seaboard.

1:55 p.m.: Flash flood warnings have been extended north and now include the Baltimore region (through 4:45 p.m.). More or less the entire area along and west of I-95 from D.C.’s southern suburbs to Baltimore’s northern suburbs are under flash flood warnings.  Reports of water rescues continue to trickle in from around the region, the latest from around Bethesda and Bowie:

(Note: a flash flood warning is more severe than a flood warning, as it conveys extreme rainfall over a very short time period)

1:40 p.m.: Rainfall totals through 1 p.m. (since Monday) are very impressive.  Dulles Airport has picked up 4.03″ (0.73″ noon-1 p.m.), National Airport 2.8″ (0.64″ noon-1 p.m.), and BWI 2.99″.  Keep in mind, Reagan National’s average rainfall for the entire month is 3.06″, which should be exceeded from this single event.

1:20 p.m.:  A flash flood warning has been issued for NW D.C., Falls Church, Fairfax, Manassas and Arlington, Fairfax and Prince William counties through 4:15 p.m. Writes the National Weather Service:


Radar indicates heavy rain cells training – or tracking over the same areas repeatedly – just west of I-95. Downpours capable of cause creeks to overflow their banks and flooding low lying areas is likely or already happening in this area.

1:10 p.m.: The recent very heavy rainfall rates have prompted a flash flood warning for Montgomery and Howard counties until 4 p.m. Writes the National Weather Service:


BethesdaNow reports vehicles trapped in water on Bradley Boulevard.

1:05 p.m.: Here’s another photo of the coastal flooding in Annapolis from this morning’s high tide.

Downtown Annapolis flooding this morning (Brian Mead via Facebook)

The next high tide in which there may be flooding issues is around 7 p.m. in Annapolis and around 10 p.m. in Old Town and the District.

12:45 p.m.:  Motorists are reporting lots of standing water and ponding on roadways – so take it slow.  ABC7’s Jaqui Jeras shot this video on I-395 near South Capitol:

Here are a few more reports of flooding in the region:

* List of flooded roads in Fairfax County

* Edwards Ferry Road in Leesburg

* Baptist Church Road in St. Mary’s County

12:35 p.m: This latest round of downpours (with embedded thunder and lightning) is causing an uptick in flooding reports.

* The National Weather Service reports that  Bradley Rd. is closed at the intersection with Fernwood due to flooding in Bethesda

* In Prince George’s County, Governors Bridge Road has been closed (before the bridge) due to high water. Motorists are advised to take an alternative route.

Here are some fresh social media flood reports:

12:30 p.m. A bit of lightning is evident in the storms cycling through the region right now, which have very heavy rain.  There may a bit of a break in the rain after around 1 p.m.

11:55 a.m.  Not only has there been coastal flooding in Old Town, but also in Annapolis, per Twitter:

11:35 a.m.  The heavy rain coming through tends to focus in narrow bands – which can lead to significant variability in totals.  For example, in the last 3 hours, here are the totals at the three airports: Reagan National 0.38″, Dulles 1.0″, BWI 0.8″. A very heavy wave of rain in Prince William County has its eyes set on the immediate metro region for the lunch hour.

10:55 a.m.:  National Weather Service reports indicate 24-hour rainfall totals of 1-2 inches (storm totals are higher, over 2 inches in many areas, see 10:20 a.m. update). Link:  List of totals

10:35 a.m.: Cameron Run in Alexandria has surpassed flood stage:

10:20 a.m.: Here are storm rainfall totals (since Monday), through 10:00 a.m.: Reagan National 2.06″, Dulles 2.79″, BWI 2.06″

Image below shows doppler radar estimated rainfall totals – in the 1-3 inch range across the region:

Doppler estimated rainfall totals since Monday (Weather Underground)

10:10 a.m.: Road closure reports are increasing. Via Twitter:

10:00 a.m.: We’re seeing spotty reports of street flooding around the area. Here are a few reports from Twitter:

9:45 a.m.: Some tidal flooding has been reported around Old Town this morning. Pictures: