PM Update: Thunderstorm threat up tonight, highest tomorrow; 4th Maryland tornado

*Flash flood watch midnight tonight through 8 p.m. Thursday*


Radar & lightning:Latest regional 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.

With all the thunderstorm talk, it might be easy to overlook that we hit 90 or higher in many spots today. This is the 6th 90+ day we’ve seen in D.C. so far this warm season. Fortunately, dew points have remained below oppressive levels thus far, thanks to a northwest wind, but they’ll creep up tonight and remain high into tomorrow.

Through Tonight: We should see a generally serene evening under partly cloudy skies and just an outside risk of an isolated storm. It’s still uncertain whether or not we’ll get storms overnight, but the odds are up as we get past sunset (30%), and perhaps up further by midnight (50%) or thereafter. We’ll be watching for any storm clusters which might form to the northwest and then drop across the area. Any of this activity might be severe, though the biggest overall threats tonight are probably potentially heavy rain and lightning. Storms or not, the air mass is soupy, with lows ranging from near 70 to the mid-70s.

For detailed discussion of the thunderstorm threat (tonight and tomorrow), please see this post: Dangerous thunderstorm set up for D.C. area Thursday; storms possible tonight as well

Tomorrow (Thursday): Any overnight activity should be gone by around sunrise if not prior, though clouds may hang around a bit. After that, we go to partly sunny skies with temperatures on the rise out ahead of an approaching low pressure and cold front. Storms may begin to form as soon as late morning to the west, with early afternoon being the preferred time around here for now, though possibly holding off until later. All types of severe weather are a risk, though damaging winds and heavy rain should be the main concerns, along with isolated tornadoes. Depending on the timing of the front and storm activity, highs should shoot for the mid-80s to low 90s.

See Dan Stillman’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.

Storms developing in the Midwest this afternoon. For a rapid-scan (1-minute update) view check out this link!

Storms developing in the Midwest this afternoon. For a rapid-scan (1-minute update) view, check out this link!

Dangerous storminess getting started: A Particularly Dangerous Situation tornado watch is up for parts of IA, MN, IL and WI until 9 p.m. CDT as the main body of the anticipated storm event gets underway. Storms are initially rather isolated, but they are expected to converge into a mesoscale convective system and accelerate east as the evening wears on. The MCS should track across the High Risk and Moderate Risk zones out to the west through the night. Ultimately, the low pressure associated with this activity should help spark our round of storminess tomorrow.

Pollen update: Trees LOW-MODERATE, grasses MODERATE-HIGH, Weeds LOW, Mold spores MODERATE-HIGH

Fourth tornado confirmed from Monday’s outbreak in Maryland: The National Weather Service office in Sterling has confirmed a fourth tornado touched down in Maryland, Monday, in Woodbine in Howard County.  The other three tornadoes occurred in Fork (northeast Baltmore County), Baltimore city, and Colton’s Point (St. Mary’s County).  All four tornadoes, with peak winds ranging from 65-80 mph, were rated EF-0, the weakest intensity on the 0-5 Enhanced Fujita scale.  More information: National Weather Service Tornado Damage Survey

Tornado as seen over Baltimore Monday (National Weather Service via WBFF-45)

Tornado as seen over Baltimore Monday (National Weather Service via WBFF-45)

Programming note: Our next update will be around 10 p.m., unless storms break out before that.

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