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Posted at 4:05 PM ET, 09/29/2010

PM Update: Rain underway, much more to come

By Ian Livingston

Flooding risk increases as we get toward morning

* Flash Flood Watch thru Thurs | Wind Advisory (eastern counties) *
* Storm Timeline and FAQ | Nicole not so tropical | NatCast (updated) *
* Outside now? Radar, temperatures & more: Weather Wall *

The front edge of the massive swath of rain that will be with us through tomorrow has been somewhat slow to advance north, but much of the area is now seeing at least light activity. More consistent light-to-moderate rain, with some heavier activity embedded, should be entering into the area over the next few hours -- but we should get through most of the commute without anything terribly heavy falling from the clouds.

Through Tonight: We should see mostly light-to-moderate rain through the evening with occasional heavier bursts. Rain then continues through the night. There may be lulls in the action, but overall the threat for heavier rain should become greater as we head toward sunrise. Temperatures shouldn't fall much from where they are now, so lows in the low-and-mid 60s.

Tomorrow (Thursday): The a.m. commute could be a nightmare as it appears we may be into the heaviest action of the event during that time and then into the midday. Localized rainfall rates as high as about 2" per hour are not out of the question. Add in some training, and you have the potential for some very high totals in spots. Winds also pick up a bit, sustained around 10-15 mph with gusts to 25 mph or so during the afternoon. Higher gusts are possible to the east of the area. Rain should begin to wind down from south to north during the early afternoon, but showers will be possible through the rest of the day. Highs reach the mid-to-upper 70s.

We will update our rainfall map this evening, but in the meantime we are thinking a widespread 2-4" with some higher totals (a bit of a bump from earlier) is likely across most of the area.

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

Tropics: Tropical Storm Nicole became the season's 14th named system today, and we remain above average through the date (and season) in that department. CWG was in touch with Phil Klotzbach at Colorado State University today and he noted the following: "From August 22 - September 29, we have now had eleven named storm formations (Danielle - Nicole). This is the most storms that have formed in the Atlantic during this period."

By Ian Livingston  | September 29, 2010; 4:05 PM ET
Categories:  Forecasts  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: NOAA: Rainfall may be "very dangerous"
Next: Tropical storm Nicole is no more


OK, I'm ready in Falls Church. Flower pots moved, trashcans inside and gutters clean. Just a mist here now.

Posted by: tbva | September 29, 2010 4:12 PM | Report abuse

Hell must have froze over, it's been raining here in Spotsy since noon time.
Was on the Potomac 2day & the approaching low pressure had the bass really feeding 4 most of the morning. Great topwater bait.
Go Hokies & Steelers.

Posted by: VaTechBob | September 29, 2010 4:35 PM | Report abuse

The OCMs are saying to be prepared for power outages. I know, what's new...

So glad I did't go to NYC; it's may be a nightmare up there.

Posted by: JerryFloyd1 | September 29, 2010 5:00 PM | Report abuse

No rain in Dupont Circle yet, so I guess I should take advantage of the late start and head on home. There will be enough rain tomorrow.

Posted by: maralenenok | September 29, 2010 5:20 PM | Report abuse

What is an OCM?

I had enough of power outages after the Sunday July and Thursday August severe thunderstorms.

Posted by: Murre | September 29, 2010 5:20 PM | Report abuse

MEH, sorry, still not getting terribly excited about this. Just check current radar - most rain currently in the metro area is peeling off to the west, and if you look at the regional radars down into the Carolinas and Georgia, the big swath heading our way appears to have a small "fork" forming once more due south of D.C., with a small sliver heading eastward over the Delmarva, and the bulk of it coming up the Appalachians. I just don't think these 3"-5" amounts are going to verify (again).

Posted by: VAStateOfMind | September 29, 2010 5:31 PM | Report abuse

Clarification: I don't think there will be multiple inches of rain in the IMMEDIATE METRO AREA. Someone's gonna get a boatload of rain - from the look of it, out to the west - I just think there's another D.C. split looming...just my two centavos.

Posted by: VAStateOfMind | September 29, 2010 5:34 PM | Report abuse

@Murre, an OCM is an on-camera meteorologist, e.g. the weather folks on our various local TV channels.

Posted by: JerryFloyd1 | September 29, 2010 5:44 PM | Report abuse

So a relative is supposed to leave DC early tomorrow am for a drive down to Atlanta. If they decide to keep this plan, would going 66 W to 81 be better than trying 95?

Posted by: see1 | September 29, 2010 5:45 PM | Report abuse

Are you drinking the koolaid on this one too? Once a week is enough isn't it?

Posted by: jojo2008 | September 29, 2010 5:58 PM | Report abuse

Thus far, this is behaving less like a tropical system than a "Miller A". Thus far, per Doug Hill, we've had 0.04" at DCA.

If today were Dec. 5th, we would have about a half-inch of snow on the ground, but with a changeover to plain old rain about midnight due to the predicted east southeasterly winds.

Posted by: Bombo47jea | September 29, 2010 6:25 PM | Report abuse

What about the possibility of severe storms with this system? Some of the TV guys are including a significant possibility, with all this moisture and a strong low riding northeastward along the old frontal boundary and a lot of potential upward motion. And, if you look at the origin of this moisture plume all the way down in the Carribean, we're talking some serious precipitable water, too. This inflow of deep tropical moisture is more or less similiar to the setup we had with the February blizzards.

Posted by: MMCarhelp | September 29, 2010 6:32 PM | Report abuse

For fun's sake - assuming this was say late January - and the same overall pattern existed, would this be an all snow event, mixed precip, or rain? And if snow/mixed, how much?

Posted by: hrc2211 | September 29, 2010 6:38 PM | Report abuse

For those skeptics, take a look at Mosaic and watch the precip stream northward, unlike earlier this week when it took a turn to the NE. I don't think this storm is going to be a washout (in the figurative sense).

Posted by: JerryFloyd1 | September 29, 2010 6:49 PM | Report abuse

clean out your gutters and make sure your downspouts are not dumping water along your basement wall.

Posted by: walter-in-fallschurch | September 29, 2010 7:02 PM | Report abuse

MMCarhelp, the severe weather risk is not necessarily super high (rated slight from DC and east), but as with the other day there will be a greater than normal shot at tornadoes if anything is able to reach its full potential. If we stay too stable at the surface (which isnt uncommon when you get a steady rain) we might not ever realize much of the potential. In these situations, tornadoes tend (though not a rule) to be smaller/weaker/shorter lived than you might see on a hot day with a cold front moving in. Still, with a warm front scheduled to be overhead or moving west you want to watch things.. and if the low pressure does go to our west there may be some enhanced risk.

Posted by: Ian-CapitalWeatherGang | September 29, 2010 7:09 PM | Report abuse

JerryFloyd1, great mosaic radar you posted, thanks for sharing that - again, though, it looks like the bulk of that precip streaming up from the south is on a general heading to the N and W of the metro area...

Posted by: VAStateOfMind | September 29, 2010 7:22 PM | Report abuse

The radar right now might be somewhat deceiving because that pattern should not continue. The low pressure system the tropical moisture is interacting with is currently showing a negative tilt so everything in front of it is lifting in a general northwest direction. Modeling has shown this is about as negative as it gets and have it transitiioning more neutral (due south to north) from here out. It's not a given where the heaviest axis sets up, but it's unlikely to go well northwest of here.

Posted by: Ian-CapitalWeatherGang | September 29, 2010 7:48 PM | Report abuse

Why is everyone getting excited about rain? I could understand if there were accompanying strong winds.

Posted by: jab00 | September 29, 2010 9:51 PM | Report abuse

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