PM Update: Heat and humidity rise on Tuesday; northern United States severe weather


Radar & lightning: Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Another day dominated by clouds and marine influenced air. In much of the year, a bit of a downer. In July, fairly welcome! We head warmer and muggier tomorrow, with only a slight passing risk for raindrops.

Through Tonight: As isolated shower or storm remains possible into early evening, though that’s mainly a risk south of town. After that, we should be partly cloudy through the night as the gray of today tends to break a bit. Lows reach the upper 60s and lower 70s. Winds are light.

Tomorrow (Tuesday): It’s a partly sunny and summery day. Makes sense given it’s summer, right? These days you never know. Highs mainly reach the mid-and-upper 80s. Humidity makes it back to the oppressive range (as if today was a walk in the park!), with dew points near or above 70 throughout. We can’t rule out an isolated storm in the afternoon, but nothing significant appears on tap. Winds blow from the south around 5-10 mph.

See Jason Samenow’s 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.


Kenilworth Aquatic Gardens on July 19. (jdavidphotography via Flickr)

Pollen update: Tree and weed pollen is low. Grass pollen is moderate, as is mold.

Related: What to do during a thunderstorm if you react to pollens and molds


(Storm Prediction Center)

Moderate Risk: The northern Plains and Upper Midwest are under the gun for severe weather this evening as a powerful belt of jet stream winds pushes across the area, in combination with extreme instability at the surface. The main concern is over parts of North Dakota, and Minnesota, where the Storm Prediction Center has placed a “Moderate Risk” and is highlighting the potential for a widespread wind event/derecho.

Storms are still getting going across North Dakota, where a tornado watch is up through the evening. The pool of fuel (CAPE) to their east is large, and it highlights the potential for a big swath of wind later.


Surface convective available potential energy (CAPE) at 4 p.m. EDT. (Storm Prediction Center)
Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank.
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