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Posted at 3:10 PM ET, 08/17/2010

PM Update: Rain arrives tonight; Heavy tomorrow?

By Ian Livingston

Flooding may be a threat by morning, especially S and E

* Flood Watch Wednesday for D.C. and generally S&E (see map) *
* Weather and war throughout history | How many 90s? Play to win *
* Outside now? Radar, lightning, temps & more: Weather Wall *

We've tacked on another 90+ day here in D.C., and we're down to 6 left to put us tied for number two all time. It looks like we won't be getting there right away though, as we drop back in temperatures for the next day or two. While it's been another warm to hot one today, humidity levels were a bit more bearable as some drier air filters in behind the cold front that moved through yesterday. Humidity should be back on the rise soon, and rain -- potentially a significant amount -- won't be far behind.

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.

Through Tonight: Moisture gathering to the south and southwest will begin to stream this way during the evening. First we'll notice clouds thicken, before showers become possible around sunset. Showers, and maybe a rumble or two, are then increasingly likely through the night. Lows reach near 70 to the mid-70s. By morning, some locations across the area could pick up .25"-.50" of rain or so.

Tomorrow (Wednesday): There are still questions as to where the heaviest rain sets up, but the morning commute could be nasty. If we get the heavy rain (with embedded t'storms) in here, it should focus on the morning and midday hours. Someone in the broader region -- greatest odds D.C. south and east -- could see a few inches of rain over a short period, which may cause flooding concerns. There is also a good chance of much less rain just to our northwest. The risk of rain, probably lighter intensity, continues through the afternoon and into the evening as moisture begins to pull away to the northeast. Highs struggle to get past the mid-and-upper 70s.

See Matt Rogers' forecast through the weekend. And if you haven't already, join us on Facebook and follow us on Twitter.

Just in case? Though it may be somewhat of an overreaction, the following message was sent out today by AlertDC regarding storminess expected through tomorrow: "The DC Department of Public Works announced today that District residents may pick up sandbags (up to four per household) at its New Jersey Avenue and K Street, SE site (entrance on New Jersey at I Street, SE). The sandbags weigh between 40 lbs. and 50 lbs. and residents will need to load them into their vehicles."

By Ian Livingston  | August 17, 2010; 3:10 PM ET
Categories:  Forecasts  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Weather and war throughout history
Next: Flood warnings for much of D.C. area this morning


This should be interesting...

By the way, it looks like you changed the radar to a wider view recently... I like that.

Posted by: spgass1 | August 17, 2010 4:00 PM | Report abuse

Sandbags?! Yikes... I don't think my property in NW is threatened with flooding at all, but it makes us all pause, doesn't it?

Posted by: Camden-CapitalWeatherGang | August 17, 2010 4:01 PM | Report abuse


We have both views, as we do on our Weather Wall as well. We pick which view to show depending on the proximity and type of precipitation.

Posted by: Dan-CapitalWeatherGang | August 17, 2010 4:02 PM | Report abuse

A limit of 4 sandbags?

If they're needed, what good are 4 going to do? Keep the doghouse dry?

Posted by: ah___ | August 17, 2010 4:15 PM | Report abuse

Well, there goes the power again I imagine. Oh well, had continuous power for four days, not a bad run for PEPCO.

Posted by: trollboy69 | August 17, 2010 4:20 PM | Report abuse

I know forecasting rain totals is tricky, but are you still estimating 1" of rain within the immediate metro area with closer to 2" south and east?

Posted by: wzitlau | August 17, 2010 4:29 PM | Report abuse

I had severe damage to my house from the storm last Thursday (a hole in the roof from where a huge tree hit it). Right now, we've got a tarp nailed down covering most of the roof. I'm really, really hoping that this significant rain will not include high winds that could dislodge the tarp. What do you think?

Posted by: lmd217 | August 17, 2010 4:47 PM | Report abuse

wzitlau, I'd say most of the area is at risk for 1-3" or so, but the highest odds seem to be D.C. and south/east. Not sure can give much more detail than that right now, maybe by later this evening once the players start showing up.

Posted by: Ian-CapitalWeatherGang | August 17, 2010 4:49 PM | Report abuse

lmd217, there should not be major wind, mostly light. I guess there could be a few gusts but hopefully not enough to cause you issues.

Posted by: Ian-CapitalWeatherGang | August 17, 2010 4:51 PM | Report abuse

CWG - based on your forecast we are NOT watering the garden this evening, even though it is dry. Hope we'll be woken up by the sound of heavy rain on the roof before dawn.

Posted by: FIREDRAGON47 | August 17, 2010 6:41 PM | Report abuse

I noticed the flood watches are posted for Fairfax (but not Loudoun or Montgomery), DC, and PG Co. (but not Howard, AA, or Charles.) This seems to be an odd pattern, such a thin line across the area for a watch. Is the rain really that focused? (I live in Silver Spring, surrounded on three sides by this watch, and on the other by my pile of basement carpet that we had to throw out after Thursday's storm. Should I be searching for sandbags?

Posted by: vtavgjoe | August 17, 2010 7:02 PM | Report abuse

Sandbagging in Washington? What's new?? Although usually the sandbagging takes place after certain types of "storms" blow up, not before.

Posted by: JerryFloyd1 | August 17, 2010 7:56 PM | Report abuse

OK....I'm not watering based on the forecast. As nasty as my sinus pressure is, I'm thinking the forecast is on target as I would like to drill a hole in my head!

Posted by: SPS1 | August 17, 2010 9:51 PM | Report abuse

4 sandbags per household! Classic DC good gubmint. Won't stop any water, but will help you get unstuck when the roads go unplowed this winter...

Posted by: KPosty | August 17, 2010 10:03 PM | Report abuse

Doubt we will c any flooding. Most times, the rainfall amounts r over estimated. Doubt there will anything more than some minor stream flooding, just don't c that much rain 2 cause any major problems. 1-2" of rain isn't going 2 cause that many problems. Much 2 do about nothing.

Posted by: VaTechBob | August 17, 2010 10:50 PM | Report abuse

I might not disagree totally with VaTech, but when you see outputs like this.. it's a lot of water falling in a short period of time. The models do often overproduce, but they are probably at least a bit more likely to be right this time of year with the extra moisture around as compared to winter when there is less overall.

Posted by: Ian-CapitalWeatherGang | August 17, 2010 10:58 PM | Report abuse

vtavgjoe, from the same model as above (tonight's 0z NAM), you can see the sharp cutoff to the northwest very well on total accumulated precipitation maps. This has been what guidance has been showing for a while in one way or another, though the "blob" has shifted a bit.

Posted by: Ian-CapitalWeatherGang | August 17, 2010 11:02 PM | Report abuse

So, we need 6 more 90+ days merely to tie for # 2...hmm, not sure it's worth it. To get actual bragging rights, we need how many to break the record? FIFTEEN? Totally not worth it. Bring on the snow.

Posted by: jhbyer | August 18, 2010 12:51 AM | Report abuse

If you've ever bicycled from Fairfax County into DC, you know it's all down hill, so it follows DC is low-down, but I bad to wonder who in the DC gubmint has a friend in the sandbag business?

Posted by: jhbyer | August 18, 2010 1:39 AM | Report abuse

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