Updated forecast: Showers and storms overnight with heavy downpours

As locally heavy rain may fall in some of the storms in a short amount of time, the flash flood watch remains in effect until 4 a.m. Please be safe out there.

This is our last update unless severe weather redevelops.

9:35 p.m. — Flash flood watch expanded to cover entire region as storms erupt in our northwestern areas

The National Weather Service has expanded the flash flood watch, previously only in effect for areas north of the District until 2 a.m., to cover the area from Prince William County north (including the Capital Beltway and the District) until 4 a.m. Storms through much of the immediate area and our northern suburbs could see extremely heavy rainfall rates as storms come though the area.

Severe storms have already flared up in Frederick County, Md. and are showing signs of extending south some. For the next hour or two, most of the storm activity should remain north and northwest of the Beltway but toward midnight the chance of storminess will increase closer to the immediate area.

8:55 p.m. — Severe thunderstorm watch until midnight

Radar and short-term model forecasts suggest storms developing to our west and northwest will expand to the east over the next couple hours. The atmosphere is sufficiently unstable that some storms could be severe with some damaging wind gusts and the outside chance of a brief tornado.

The National Weather Service has issued a severe thunderstorm watch until midnight, although storms with heavy rain could continue until 2 or 3 a.m. A severe thunderstorm watch means conditions are favorable for severe storms and you should monitor conditions. If a severe thunderstorm warning is issued, it means a severe storm is imminent and you should seek shelter.

6:20 p.m. — Flash flood watch issued north of the District until 2 a.m.

Showers and storms this evening, probably heaviest north of the District, could cause some pockets of flash flooding. While average rainfall amounts of one-half to one inch are expected, “thunderstorms will contain very heavy rainfall with rainfall rates around 1 to 3 inches per hour,” the National Weather Service wrote in its flash flood watch statement. “Localized rainfall amounts of 2 to 4 inches are possible.”

Storms may develop after around 9 p.m. and could be rather numerous into the predawn hours. Remember never attempt to cross a flooded road in your vehicle. Turn around.

Original article from 4:45 p.m.

Highs in the mid- and upper 80s today felt on the summery side, thanks to relatively high humidity ahead of a cold front. That front is moving our way from the west. As it passes, it’ll deliver some showers and storms. Rain could linger into Thursday, but conditions should generally turn better with time, if they do.

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Through tonight: Although a random pop-up is possible earlier, scattered showers and storms are probable late this evening and tonight. Some of this activity could be strong, with the main risks being heavy rain, lightning and perhaps isolated damaging wind. As much as half an inch to an inch could fall where storms are consistent, with other spots seeing considerably less. Lows will be in the mid-60s to about 70.

View the current weather at The Washington Post.

Tomorrow (Thursday): There could still be scattered showers around in the morning. Otherwise, skies will turn clearer with time as rain becomes less likely into the midday. A pop-up late in the day isn’t impossible. Afternoon temperatures will aim for the mid-70s to about 80, depending on how quickly we get rain to end and sunshine to break through. Winds will be from the northwest around 5 mph.

See Dan Stillman’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 Gridlock.

Pollen update: Weed pollen, mold spores and grass pollen are moderate/high. Tree pollen is low. The first half of September typically features the peak of ragweed pollen, if you’re sniffling these days.

Gulf system: Tropical Storm Mindy has formed in the northeast Gulf of Mexico as a small low-pressure system approaches land. Tropical storm conditions are possible for parts of the Florida Panhandle as it comes ashore tonight. Heavy rain will follow the storm inland over parts of Georgia and South Carolina into Thursday. The same cold front passing this region will help sweep it out to sea on Friday.

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