A coastal storm develops and moves by the region tonight and Thursday. (Capital Weather Gang and Pivotal Weather)

Washington’s ten-day dry streak comes to an end tonight as low pressure rides up the coast and washes the region with several inches of rain. More than just an end to a dry spell, it’s also the first legitimate coastal storm for the capital this year.

The rain begins after dark, moving in from the south late this evening and early overnight. When it’s all said and done Thursday, widespread totals of one to two inches will have fallen across the Washington region.

Today, low pressure is taking shape off the Carolinas. While skies in the Washington area have featured filtered sunshine, the first signs of this storm have shown up in the form of higher clouds.


Precipitation forecast as of Wednesday morning from the Weather Prediction Center.

The area should stay dry through and even beyond sunset, but showers may move into Southern Maryland a few hours after the sun goes down. From there, the rain progresses northward through late evening. Raindrops could be falling by 10 to 11 p.m. or so, but the steady, widespread rain should generally hold off until after midnight.

With overnight temperatures dipping mainly into the upper 30s or mid-40s, and air aloft that is too warm to support frozen precipitation, this should be mostly or fully rain. A little sleet, or perhaps a few snowflakes, can’t be ruled out as it starts.

Some of the heaviest rain may target Thursday’s morning commute. Rain is, of course, better than snow, but it’s probably best to plan on lowered visibility, as well as ponding on roads for the morning drive.


Flash flood guidance generally suggests a few inches of rain is needed for flooding, but some isolated flooding is possible. (Mid Atlantic River Forecast Center/Mid Atlantic River Forecast Center)

Rain continues at its heaviest and steadiest from around sunrise through midday. Some spots could see as much as a half-inch to an inch of rain in this period alone. Although this dry spell is the longest since an 11-day stretch in December, and there’s been no significant rain in about three weeks, flash flooding can’t be ruled out. This is especially so in urban areas.

On Thursday afternoon, low pressure is close by and beginning to pass the region. Rain should begin to taper at this time. Additional totals from midafternoon into evening should generally be on the lighter side, but it will also stay damp, and drizzle may persist through sunset.

Highs Thursday are mainly in the 40s, but they may top 50 degrees, especially in the city and south or east.

This storm isn’t too strong as it passes, so winds are not expected to be a major concern. They’re out of the east and northeast around 10 to 15 mph during the day, with some higher gusts. It may be that winds increase after the storm passes and into Friday, as it will strengthen while heading northeast.


Low pressure forecast tracks from the Weather Prediction Center. (NWS/NWS)

From our area and north, the storm will probably track near the coast. Some shifts in track are still possible. But there is a general lack of cold air — partly because of the late calendar date and partly because of the absence of a cold high pressure to the north.

Much of the coastal plain from North Carolina to Maine can expect half an inch to an inch or more of rain from this system. The maximum areas of precipitation occur to the north and west of its track. This seems likely to include the Washington area and then northward through eastern Pennsylvania and New York, as well as western New England.

Accumulating snow is relegated largely to mountains in New England and northern New York, although light accumulation is possible in the Appalachians of the Mid-Atlantic and perhaps on the tail end of the event in parts of southern New England.