Wednesday, June 13, 2007

Sit and Spin
Pesky low pressure to spawn evening storms

** Severe Thunderstorm Watch in Effect Until 9 PM **


Warm, humid, scattered thunderstorms. The persistent low pressure area off the coast that Dan noted earlier today continues to spin counterclockwise, sending a moist flow onto the coastal plain and piedmont of the Northeast and Mid Atlantic regions. The scattered thunderstorms erupting in this flow are once again moving from northeast to southwest across the Washington DC metro region, prompting severe thunderstorm warnings earlier this afternoon for portions of MoCo and Prince George's. Hail up to 1" was reported from the Four Corners and White Oak areas of Silver Spring and NASA in Greenbelt, as well as Herndon, Reston, and Chantilly in Virginia.

A large batch of storms scattered across central and southeastern Pennsylvania is also moving southwest and is likely to affect portions of the metro region in the next couple of hours. The leading group of these storms was already reaching Baltimore City and County by 4:30. Temperatures peaked just over 80° at noon at National, but tumbled to the upper 60s in thundershowers by mid afternoon.

Conditions should be somwhat drier and cooler tomorrow, but temperatures will warm over the weekend.

Pictured: Map of surface pressure (solid lines) and 500 mb height (color shading) this morning over North America and adjacent Atlantic from Unisys. Click here for more explanation.

Tonight and Tomorrow

Scattered showers diminishing, turning cooler. Some scattered showers and thunderstorms may continue through the evening. Otherwise, tonight will be partly cloudy with lows from the low 60s downtown to some upper 50s in the cooler 'burbs. Tomorrow will be mainly cloudy with highs only 69-74°.

For the outlook through Friday and the weekend, scroll on down to Dan's post below.

Tropical Topics: 3-E is History

Depression 3-E in the eastern Pacific has been given last rites. The Atlantic is similarly comatose.

Climate Corner: How Many College Presidents Does It Take to Change a Light Bulb?

Yesterday's WaPo ("Colleges Pledge to Back Climate Initiative") described efforts by 280 college presidents to "raise awareness about global warming and limit their institutions' emissions in moving toward 'climate neutrality'." Local institutions participating include UMD, James Madison, and Howard Community. The subject was also covered by the Baltimore Sun and Chronicle of Higher Education (behind the pay wall).

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Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.