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Posted at 10:30 AM ET, 07/31/2009

Forecast: Sticky? Definitely. Stormy? Maybe.

By Camden Walker

Today's heaviest rain tracks north of D.C.

* Severe T-Storm Watch Until 9 PM | Cloud-to-Cloud Lightning *
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Today: Mostly cloudy and sticky. 60% chance of mainly p.m. showers and storms. Mid-80s. | Tonight: Evening showers/storms? Near 70. | Tomorrow: Partly sunny. A little less humid. Upper 80s. | Sunday: More clouds than sun. Humid. 50% chance of showers/storms. Mid-80s. | A Look Ahead


We're likely to see some showers today, and maybe a few strong storms, but the steadiest rain should miss us to the north. Showers and storms may bother us again on Sunday. Otherwise, we're in the thick of it in terms of humidity. As we start a new month, I can confirm that it will indeed feel like August for the forseeable future, though no extreme heat wave is imminent. Have you noticed talk of our non-humid and not-so-warm summer has waned?

Radar: Latest regional radar loop shows movement of precipitation over past two hours. Powered by HAMweather. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Today (Friday): Sticky feeling today with mostly cloudy skies, highs climbing toward the mid-80s, and the chance of a passing shower or two through early afternoon. Showers and storms become more likely (60% chance) from mid-afternoon into evening. But the heaviest rains should veer north of the area. Watch for gusty winds, heavy rain and maybe hail with any storms that do come through, as well as a slight tornado chance. Outside of storms, afternoon breezes increase to around 10-20 mph from the southwest. Confidence: Medium

Probability: 60%
Coverage: Scattered

Tonight: Some showers and storms may linger into the evening (50% chance). But after midnight, some partial clearing is possible as breezes briefly come out of the west and northwest. Lows around 70 through most of the region. Confidence: Medium

Any weekend storms? Keep reading for the forecast into early next week...

Tomorrow (Saturday): Morning breezes from the northwest could temporarily reduce the humidity a notch, though it should still be at least in the moderate range. Skies will probably be at least partly sunny with highs in the upper 80s, but patches of cumulus clouds may blossom by afternoon with an isolated late-day shower or storm not impossible. Confidence: Medium

Tomorrow Night: I know it's a good night to go out on the town, but consider the pocketbook umbrella with a 20-30% chance of an isolated shower or storm. Winds from the south/southwest will be light, but they'll feel somewhat balmy. Lows get down to around 70 in most spots. Confidence: Medium

Sunday: Shower and thunderstorm chances increase again come Sunday. Expect a 50% chance, especially by afternoon as the atmosphere percolates. Otherwise, I think we'll have more clouds than sun. Humidity should be back in full force. So highs in the mid-80s will likely feel quite muggy. Confidence: Low-Medium


A fairly "broken-record" end to our weekend on Sunday night with a 50% chance of some showers and storms. Skies remain mostly cloudy otherwise. Lows in the fairly familiar upper 60s to low 70s. Confidence: Low-Medium

Expect highs around the upper 80s on Monday and Tuesday. Each day has a 30% chance or so of seeing a shower or storm. I think I'll plan to take along my travel umbrella. Confidence: Medium

By Camden Walker  | July 31, 2009; 10:30 AM ET
Categories:  Forecasts  
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Next: Summer 2009: Northwest Sizzles, Texas Withers


Question for the Gang...with helicity rates running high and the airmass so tropical in nature, would any tornados that may spin up today tend to be weaker and rain shrouded, much like you see in the front right quadrant of a landfalling tropical system? We don't often have a tornado threat into late July/early August without a tropical system...

Posted by: DullesARC | July 31, 2009 8:34 AM | Report abuse

Hey DullesARC, I don't see a great threat from tornadoes today. But if the winds do bend with the off-chance of a very tall, strong thunderstorm today (1-2% chance of a 30,000ft+ CN in my opinion) accessing some of that helicity; yes, weak. weak is the key word. And certainly they would be involved with the southerly rain shield of the thunderstorm as is typical in the Mid-Atlantic region. But I view this as an academic discussion here. Nothing that I really see transpiring this afternoon! But I do miss talking about helicity :)

Posted by: Camden-CapitalWeatherGang | July 31, 2009 8:54 AM | Report abuse

Camden, I think we rarely see a "great threat" for tornadoes but this is one of the better of the year -- along with Wednesday. SPC upped the prob from 2% chance to 5% chance within the last hour.

Posted by: Ian-CapitalWeatherGang | July 31, 2009 9:10 AM | Report abuse

Hi guys - Seeing much more sun today than on Wednesday (I'm in Alexandria, on the river, just south of the airport). Does this extra sun increase our chances for storms / rain here in the immediate metro area?

Posted by: todd27 | July 31, 2009 9:26 AM | Report abuse

Thanks Camden - that makes a lot of sense...I figure that we have about 5-7 days a year where the conditions come together for the "possibility"...and today, unfortunately is one of them. Keep your eyes and ears open today ya'll, it may be a funky afternoon!! 5% is a statistically significant number - one in twenty? Probably better than the odds of both the Nats and O's winning tonight :)

Posted by: DullesARC | July 31, 2009 9:40 AM | Report abuse

There is a Gale Warning posted for the bay. That's got to be pretty rare for a non-tropical situation in July. Although, it probably speaks more to our wimpy gale warning criteria than any thing else.

Posted by: praxis22 | July 31, 2009 10:22 AM | Report abuse

Guys - fascinating discussion on the tornado chances today - how about we just get some measurable precipitation? This whole week of storm hold will wind up producing nothing - so far IAD only 0.06 in pathetic.

Posted by: LoudounGeek | July 31, 2009 10:46 AM | Report abuse

Nope, I see the DC split happening again today. The rain loves Pennsylvania at this time of year.

Posted by: rocotten | July 31, 2009 11:01 AM | Report abuse

Any sunshine is a positive for storm development -- on that front things are looking better than Wed around here. Overall it's a slightly better setup I think given the low track closer to the area. Problem with these "warm sector" events is that they are generally fairly isolated/scattered on intense activity. Certainly could be a case where there is not that much rain areawide. The similar setup earlier in the week did produce tornadoes up to EF2, so that's not terribly weak for the east coast.

Posted by: Ian-CapitalWeatherGang | July 31, 2009 11:04 AM | Report abuse

Area being monitored for a watch now.

Posted by: Ian-CapitalWeatherGang | July 31, 2009 12:13 PM | Report abuse

LoudounGeek, I'm just fine with the light precip. thus seem to forget that we were awfully close to ark-building just a month or two ago! [I also have a scheduled dance tonight.]

The continual sunny weather here increases the threat of something severe later this afternoon...I thought that a cloud deck advancing from the NW around 10:30 this morning would dampen severe activity around here, but the sun keeps coming out. We seem to have another cloud deck moving in; this could be the stormy weather arriving. Radar seems to show that the band of active weather is somewhat narrow.

Posted by: Bombo47jea | July 31, 2009 1:16 PM | Report abuse

Question for you guys. I stumbled onto your website because I was in the Sterling area yesterday afternoon where we were I believe in the middle of a formation of a tornado cell. I was looking for any archived radar for that area at the time of question.

We were on Route 7 heading toward Leesburg (between Rt 28 and Landsdowne). It was about 2:15 pm(7/31/09). It was clearly obvious that we were heading into a storm. Dark clouds, but no lighting or rain yet.

The 3 lanes of traffic came to a complete stop. Unable to bale out anywhere we just sat there for a few moments.

About 100 yards before us was a bridge currently in the building stages. I noticed a bit of dust blowing up from the construction site. Trying to figure out what they were doing before a storm, I kept watching. Then it kept getting larger...this is on the right side of our van at this point. The dust cloud (aka red Virginia clay) became so large that it started to blanket the cars ahead of us like a large big a jet plane. As we are watching this cloud going from our right to left, a huge gust of wind starts coming at us (we are way behind this dust ball) and there were trees in the median to the left of us. The dead limbs snapped and starting heading for us. The daughter saw it and actually let out a yell. I moved up and then was hit with a large orange construction barrel that the black ring weighted it was just spinning around in the road like it was a Frisbee. Then that was it. This all took about 45 seconds.

What the heck was that???? The beginning formation of a cell??

It then down poured for about a hour and half after that.

Any records of this on radar somewhere?


From: A Family Frighten by Mother Nature

Posted by: joannesmith1 | August 1, 2009 9:11 AM | Report abuse

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