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The heat and humidity climbed up a notch today, with afternoon heat indices near 100.  On Wednesday, it gets even hotter.  With all of this steamy air around, we need to monitor the thunderstorm potential, which is slight this evening but becomes a better bet during the day Wednesday.

Through Tonight: Muggy this evening, with a 20-30 percent chance of thunderstorms.  The highest chances concentrate in our western areas; activity closer to town should be isolated.  After dark, the storm threat fades.  It doesn’t cool down appreciably overnight, with lows from near 70 in our cooler suburbs to the mid-to-upper 70s downtown.  Light winds from the south around 5-10 mph.

Tomorrow (Wedneday): Hot and very humid, with numerous thunderstorms developing in the afternoon and evening hours.  Highs reach the mid-90s, and it feels as hot as 100-105.  The storms that develop could produce very heavy rain, strong – possibly damaging – winds, and hail.  We’ll take a deeper look at the thunderstorm potential in updates tomorrow.  Note that the National Weather Service Storm Prediction Center has placed us in a slight risk zone for severe weather.

See Matt Rogers’ forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter . For related traffic news, check out Dr. Gridlock.

Pollen: Tree counts are LOW, grass counts are MODERATE, weed and mold spore counts are LOW-MODERATE.

Tropical update: Satellite imagery suggests Arthur has become better organized throughout the day.  Its pressure has fallen some and we wouldn’t be surprised to see its estimated maximum sustained winds increased in the next advisory from the National Hurricane Center

View of Arthur at 3:45 p.m. ET (NOAA)


Update, 4:55 p.m.: The National Hurricane Center estimates Arthur’s maximum sustained winds are now up to 50 mph (from 40 mph this morning) with a minimum pressure of 1003 mb (down from 1007 mb this morning)

I put together a brief video overview earlier this afternoon:

The first tropical storm of the 2014 hurricane season will visit the East Coast between now and the July 4 holiday weekend. The Post's Jason Samenow explains where and when it will hit, and whether you'll need to change your weekend plans. (Tom LeGro and Jason Samenow/The Washington Post)