* Severe thunderstorm watch until 10 p.m. for Fauquier, Loudoun and Frederick counties | Heavy afternoon rain floods roadways across the Washington area *

3:45 p.m. – Most rain/storms pushing east of Beltway. Watching and waiting what happens next

Rain continues to fall east of the Beltway, but outside Southern Maryland – where it is falling heavily – the intensity has generally eased.

From the Beltway and to the west, the sun has come back out and, while widely scattered showers and storms can’t be ruled out over the next few hours, it should be mostly dry. The late day heating may help provide fuel for storms that develop this evening, although models suggest they’ll be most numerous and intense in our far western and northwest areas between 6 p.m. and 10 p.m. or so, where a severe thunderstorm watch is in effect. Closer to town, storms may end up a bit more scattered.

While the heaviest rain has already occurred around the Beltway, a flood warning continues – as it does to the east, where it’s still raining. These warnings may be lifted in the next couple of hours, but lookout for areas of high water, especially near creeks and streams.


Areas under a flood warning. (National Weather Service)

Several reports of flooded roads and streams came in earlier this afternoon:

Through 3 p.m., Reagan National Airport had picked up 1.92 inches of rain, not far off the record for August 21 of 2.12 inches set in 1906 downtown.

This is the last update in this post. Stay tuned for PM forecast update, to be published between 4 and 5 p.m.

2:45 p.m. – Severe thunderstorm watch until 10 p.m. for western counties

Frederick, Loudoun, and Fauquier counties  and locations to the west are now under a severe thunderstorm watch until 10 p.m. Bands of vigorous storms are predicted to intensify through the afternoon and into the evening as a cold front approaches the region. Damaging wind gusts are possible, and a short-lived tornado isn’t out of the question.

While we can’t rule out storms, a few of which may be strong, to the east over the immediate area, the storms this afternoon have sapped the atmosphere of some of its energy and the front isn’t expected to arrive until well after dark, when less fuel for storms will be available.

For earlier updates, which have now expired, scroll down to the bottom of this post.

From 5 a.m.

TODAY’S DAILY DIGIT
A somewhat subjective rating of the day’s weather, on a scale of 0 to 10.

5/10: Polite temperature resumption with some rude thunderstorm interruption

EXPRESS FORECAST

Today: Partly to mostly cloudy, midday to p.m. storms. Highs: 79-85
Tonight: Evening storms, cloudy overnight. Lows: 68-73
Tomorrow: Partly sunny, shower chance. Highs: 84-88

View the current weather at The Washington Post headquarters.

FORECAST IN DETAIL

A cold front approaches today and triggers thunderstorms later this evening. Humidity starts to decrease late tonight. Thursday to Saturday looks fantastic, with temperatures, humidity and sunshine all very fine. Heat and humidity turn up a notch by Sunday, setting the stage for a return of hot August weather next week.

Listen to the latest forecast:

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Today (Tuesday): Partly to mostly cloudy skies with moderate humidity and scattered showers or thundershowers by midday into the afternoon (very scattered, hit-and-miss activity). Highs manage to reach around 80 or into the middle 80s in spots. More widespread thunderstorms late this afternoon into the evening might be strong to severe, with gusty winds and heavier downpours. Light winds (except around thunderstorms) come from an easterly direction. Confidence: Low-Medium


Tonight: Scattered evening thunderstorms could again be heavy/severe (with gusty winds and heavy downpours), ending by late evening. Humidity should start to drop off toward dawn as temperatures dip to lows in the upper 60s to low 70s. Light winds overnight come from a westerly direction. Rainfall totals for the whole day range from a trace to a half-inch, with locally heavy amounts up to one inch. Confidence: Medium

Follow us on Facebook, Twitter and Instagram for the latest updates. For related traffic news, check out Gridlock. Keep reading for the forecast through the weekend . . .

Tomorrow (Wednesday): Mixed cloud cover, with the best chance for sunshine in the afternoon. Lower humidity makes the middle 80s range more bearable, but we still run the chance of scattered showers, especially on the east and south sides of the area. Light winds from the northwest at 5 to 10 mph. Confidence: Medium

Tomorrow night: Clearing, cooling and turning more comfortable, with lows ranging through the 60s and dew points dropping off to drier levels. Light breezes again blow from the cooler north to northwest direction. Confidence: Medium


A duck at Constitution Gardens on the Mall on Sunday. (Miki Jourdan)

A LOOK AHEAD

Thursday and Friday are a pair of spectacular days, with highs in the lower to middle 80s and low humidity under mostly sunny skies. Lows both Thursday and Friday night should range through the comfortable 60s under mostly clear skies — and the outer western and northern suburbs could dip slightly more, into the upper 50s. Wow! Confidence: High

Our weekend is a split story. Look for Saturday to continue our very nice weather, with highs in the lower to middle 80s under mostly sunny skies and with relatively low humidity. Dew points and a few clouds creep back into play Saturday night. Lows should be in the middle 60s to around 70. Sunday sends back some summer, with humidity increasing to moderate levels and highs rising toward the upper 80s or 90 along with partly sunny skies. A late-day shower or storm is possible Sunday, too. Confidence: Medium

Summer is not finished with us yet: Next week’s temperatures look to range in the low-middle 90s with moderate to high humidity.

Expired updates from earlier rain/storm coverage

2:30 p.m. – Rain totals mount, reach one to three inches as flood warnings continue

The heaviest rain has mostly shifted north and east of the District, but some of the rainfall totals are impressive.

Doppler radar showed widespread amounts of 0.5 to 1.5 inches inside the Beltway, with heavier pockets up to three inches to the west along Interstate 66 around Centreville and to the southeast near Clinton.

Through 2:20 p.m., Reagan National Airport had picked up 1.28 inches of rain. Remarkably, Andrew Air Force Base registered 3.18 inches in a single hour between 1 and 2 p.m.

1:55 p.m. – Flood warning expanded over eastern part of District and Prince George’s County

Some of the heaviest rainfall has now shifted east of downtown Washington, prompting a flooding warning for the eastern half of the District and all of the Prince George’s County, until 8 p.m.

Up to 1 to 2 inches of rain have already fallen and another one to three inches cannot be ruled out.

Much of the immediate D.C. metro area is now under a flood warning until this evening, although we expect the heaviest rain to end by late this afternoon.

Avoid driving routes near creeks and streams that may overflow. If you encounter a flooded road, turn around – as the water level is difficult to judge and you may become stranded and require rescue.

1:18 p.m. – Flood warning for central Fairfax County into NW D.C.

Torrential rain has now dispensed up to two inches of rain around Centreville, prompting the National Weather Service to issue a flood warning for central Fairfax County, Falls Church, Alexandria, Arlington, Manassas, central Prince William County, and western parts of the District until 7:15 p.m.


Area under flood warning until 7:15 p.m. (National Weather Service)

Additional heavy rainfall is possible over the next hour or so.

“Excessive runoff from heavy rainfall will cause flooding of smallcreeks and streams, urban areas, highways, streets and underpasses as well as other drainage areas and low lying spots,” the Weather Service warns.

12:55 p.m. – Storms pushing inside Beltway

The warm front, which we expected to move through this morning, has slowed down and strong thunderstorms have developed right along it as it pushes north. Storms with lightning and heavy rain, which have already unloaded up to an inch of water in some of our south and west areas, are moving inside the Beltway.

A quick half inch to inch or so of rain is likely with these storms, which could produce some ponding of water on the roads and even isolated pockets of flooding in poor drainage areas.

These should pass through by midafternoon in the immediate area and our northern areas by late afternoon.

After these storms have moved through, the atmosphere may be somewhat worked over, reducing the chance of strong to severe storms when the cold front comes through late tonight. Showers and storms along this front are most likely between about 9 p.m. and midnight, most likely west and north of the District.