Community Corner

Derecho Conditions Heading for Northern VA?

Meteorologists are in disagreement: Some say weather patterns are right for a straight-line windstorm this week; others say it's unlikely.

Update, Wednesday, 2 p.m.

The National Weather Service has issued a flash flood watch for Fairfax County from 12 a.m. Thursday to Thursday evening.

The NWS says showers and thunderstorms will move across the region Wednesday night and produce heavy downpours and rainfall amounts from 1 to 2 inches.

Find out what's happening in Restonwith free, real-time updates from Patch.

With the ground already saturated from heavy rainfall this week, as little as an inch of rain in an hour could produce flash flooding of streams and in low lying areas.

Original story, Wednesday morning

Find out what's happening in Restonwith free, real-time updates from Patch.

Reston residents won't soon forget last year's deadly derecho that struck the area June 29.

That late Friday-night storm brought high winds and heavy rain. It killed at least two people and knocked out power to more than a quarter-million homes in Northern Virginia. The downed trees, multi-day power outages, problems with 911, cell phone service interruptions and triple-digit temperatures created a grueling mix for the area.

Now, some meteorologists are talking about a weather system that may have the potential to spawn another derecho, possibly late Wednesday or Thursday.

Fortunately, any power outages related to these coming storms may be easier to handle, as high temperatures are projected to be in the low to mid-80s over the next 10 days—not 100-plus degrees.

Of course, meteorologists don't always agree on weather forecasts.

Here's a breakdown of who's saying what:

Alex Sosnowski, senior meteorologist from AccuWeather: 

"Complexes of strong, drenching and locally severe thunderstorms will reach from parts of South Dakota and Nebraska to Illinois, Ohio, western Pennsylvania and the Virginias during the middle of this week.

Part of this area could be hit by an intense thunderstorm complex, known as a derecho."

Sosnowski, replying to comments about possible fear-mongering by uttering the word "derecho" in his forecast, said: "It is our duty to warn people of potential dangerous weather conditions. The weather pattern favors multiple MCSs (Mesoscale Convective System) spanning late Tuesday to Thursday afternoon. Of these there is a 'chance' one morphs into a derecho. Because forecasting the exact starting point of an MCS is difficult and exactly where the complexes will turn to the right of the flow, we can't say dead on which locations will be hit the hardest."

Jason Samenow, Capital Weather Gang in a post Monday headlined "Ratcheting down the derecho hype, but recognizing the risk (late Wednesday)"

The Capital Weather Gang's Jason Samenow examines the forecasts and concludes that he is "unconvinced there’s reasonable confidence D.C. will experience derecho conditions, and I cringe at sounding the alarm so soon."

Capital Weather Gang's Matt Rogers does not mention the "d word," but possible "strong winds" for late Wednesday:

"Another super-soaker system surges into the area  with potentially widespread heavy storms yet again (which *might* contain some strong winds). The models vary on timing and details, but we should be especially wary anytime after 8 p.m."

Greg Forbes, The Weather Channel forecast for Wednesday:

"Scattered severe thunderstorms, possibly in clusters or even a derecho (widespread damaging wind event associated with a bow echo thunderstorm pattern) in northeast IA, south WI, north half IL, north IN, south MI, OH, southwest PA, north and central WV, MD, DC, north VA."

Do you think meteorlogists are sounding the alarm too early, or do you like advance warning even if dire weather forecasts change for the better? Tell us in the comments. 


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