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Posted at 5:00 AM ET, 09/29/2010

Forecast: Heavy rain takes aim on D.C. area

By Dan Stillman

Exact rain totals & timing uncertain; at least 1-2" likely

* Flash Flood Watch late tonight through Thurs. evening *
* Tropical system eyes East Coast | The rain that wasn't | NatCast *
* Outside now? Radar, temps & more: Weather Wall *

updated at 12:20 p.m.

Today's Daily Digit
 
A somewhat subjective rating of the
day's weather, on a scale of 0 to 10.

 

Highs near 70 to low 70s are comfy. But uncertain arrival time for rain makes planning difficult.
 
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EXPRESS FORECAST

Today: Thickening clouds. Chance of p.m. showers. Near 70 to low 70s. | Tonight: Increasing chance of rain. 60s. | Tomorrow: Rain, heavy at times. Breezy. Mid-70s to near 80. | A Look Ahead | Get Express Forecast by E-mail

FORECAST IN DETAIL

One good thing (among the many bad things) about heat and drought -- they are relatively easy to forecast. This week's dramatically different weather pattern has brought not only opportunities for beneficial rain, but also increased chances for forecast errors. That trend continues with the potential for flooding rains tonight and tomorrow as a tropical system tracks up the East Coast (losing its tropical characteristics as it does), but some uncertainty about the location of the heaviest amounts, when the first showers arrive and when the steady rain begins.

Today (Wednesday): Any patches of morning sun give way to increasingly overcast skies and highs from near 70 to the low 70s. The leading edge of the storm system approaching from the south may give us some afternoon (40% chance) or evening (50% chance) showers. Confidence: Medium

Tonight: A 50% chance of showers this evening increases to a 70-80% chance of steadier and heavier rain overnight with overcast skies and lows in the 60s. Confidence: Medium

How much rain and when? Keep reading for the forecast through the weekend...

Tomorrow (Thursday): The heaviest rain with this system falls from late tonight into or through Thursday afternoon along with the chance of isolated thunder. With most models showing the center of the precipitation shield passing over or near the metro area, a solid 1-2 inches is looking like a good-bet minimum (even if the center line ends up shifting a bit) with 2-3"+ and flash flooding possible for at least some locations. Winds shouldn't be a major issue with this storm, but could occasionally gust to near or over 30 mph as highs reach the mid-70s to near 80. Confidence: Low-Medium

What about the coast? On its expected track (or a slight variation thereof), similar rain totals are anticipated on the Eastern Shore. The rain combined with an extended period of onshore winds, sustained near 20-30 mph at times, could result in moderate coastal flooding and erosion.

Tomorrow Night: The rain should end or become spotty by evening as the storm continues north up the coast. Winds from the northwest begin to drain the mugginess out of the air with lows dipping to the 60s with maybe some upper 50s in the suburbs. Confidence: Low-Medium

A LOOK AHEAD

Can't rule out a lingering morning shower on Friday. But more likely we'll see clearing skies with occasionally gusty breezes from the northwest and highs in the low-to-mid 70s. It's a comfortably cool Friday evening with temperatures falling through the 60s and eventually to overnight lows in the 50s (downtown) to near 50 (suburbs). Confidence: Medium

Steady breezes from the north/northwest provide a cool and partly sunny weekend. Highs probably only make the 60s to near 70 on Saturday and 60s on Sunday (lows in the rather cool 40s to near 50 Saturday night) as autumn asserts itself. Keep in mind that with the atmospheric setup we expect this weekend, it's not uncommon to see a fair amount of afternoon clouds and even a sprinkle or light shower. Confidence: Medium

By Dan Stillman  | September 29, 2010; 5:00 AM ET
Categories:  Forecasts  
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Next: Tropical storm Nicole not so tropical

Comments

Waiting at the bus stop tomorrow should be interesting...

I can't wait for those highs in the 60s later on next week!

Posted by: Yellowboy | September 29, 2010 6:24 AM | Report abuse

Wow.... your RSS feed sent me for a loop this morning. The three articles I'm seeing right now are: "Alert: Weekend snow threat growing", "Forecast: Cold is here, weekend snow threatens" and "Weekend snow prospects increase".

At first I saw that and I thought, "Well, maybe a flurry or something in the mountains? But really??" Imagine my surprise when I opened the article and there was a significant chance for over 1 inch of accumulation.

Then I thought it was an April fools joke... but it's not April. Then I checked the date of article... 17 December 2009. Ahhh, the beginning of a fantastic snow season.

Oh, and fyi, your RSS feed is screwy :)

Posted by: B-Kraemer | September 29, 2010 7:41 AM | Report abuse

The past storm turned out to be quite beneficial in many areas http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=PNS&format=CI&version=1&glossary=0&highlight=off

But some areas got gypped notably Fredericksburg and north into PW county and into DC.

Posted by: eric654 | September 29, 2010 7:44 AM | Report abuse

WTF is with this forecast? Rain from TD16 tonight? NHC doesn't forecast this system to reach DC until late Thursday night.

Posted by: Langway4Eva | September 29, 2010 7:46 AM | Report abuse

@Langway4Eva

wow, that was loud.
show us the link from NHC.

Posted by: LoudounGeek | September 29, 2010 7:52 AM | Report abuse

With up to 5" inches of rain and 50 MPW winds predicted in NYC, decided not to head up to the Wet Apple.

So, please keep us updated re: the pending storm and congratulations to Jason on his full-time assignment here and the snow groupies hope he has plenty of opportunities this upcoming winter to use the SLCB.

Posted by: JerryFloyd1 | September 29, 2010 8:10 AM | Report abuse

Addendum to above, the NWS is saying winds could gust up to 60 MPH in NYC tomorrow because of the a high pressure area anchored in the North Atlantic interacting with the storm. Definitely, fuggedaboutit.

Posted by: JerryFloyd1 | September 29, 2010 8:20 AM | Report abuse

Is there a definition of drought-buster?

How much rain do we need to get out of the drought?

Either way, this is much needed rain, and we will still get a good weekend.

Posted by: jaybird926 | September 29, 2010 8:26 AM | Report abuse

jaybird926 - if we get 2", we can call this one a drought-denter, how about that? Some places in the panhandle of WVA & northwest VA need many more inches of rain to be out of moderate to severe drought :-/

Posted by: Camden-CapitalWeatherGang | September 29, 2010 8:31 AM | Report abuse

@Langway4Eva

There is rain associated with TD16 - or at least the tropical flume of moisture feeding it -- way out ahead of it which has already reached Richmond, Va. See the national radar: http://www.weather.gov/ridge/Conus/full_loop.php

Also, by the time the depression or its remnants reach our latitude, much of the rain will be done. Most of the rain will fall ahead of the actual low pressure center

Posted by: Jason-CapitalWeatherGang | September 29, 2010 8:48 AM | Report abuse

CWG, so how come in a year when many tropical storms and hurricanes have veered away from the East Coast, here we are almost into Oct. and we are about to get hit by a tropical depression? Did someone forget to change the batteries in the force field that has been pushing these things away? This seems like another aqddition to the weirdest weather year in this region in years.

Posted by: VikingRider | September 29, 2010 8:57 AM | Report abuse

It can rain all it wants when I'm at work during the week, as long as we get a good weekend & it seems like we will!

Posted by: wadejg | September 29, 2010 9:04 AM | Report abuse

@VikingRider

CWG's hurricane expert Grecovered this in a post last week: http://voices.washingtonpost.com/capitalweathergang/2010/09/hurricanes_keep_avoiding_us_wi.html

Posted by: Jason-CapitalWeatherGang | September 29, 2010 9:23 AM | Report abuse

Ensemble model runs indicate 90-100% chance of at least 2", and 50-60% chance of 4" in Metro region

Posted by: SteveT-CapitalWeatherGang | September 29, 2010 9:58 AM | Report abuse

Jason, but the winds won't be as gusty here as along the coast, correct? Actually, I don't know if the high/low pressures gradient interaction will affect the Delmarva much as it will further to the NE.

Posted by: JerryFloyd1 | September 29, 2010 10:06 AM | Report abuse

That's a lot of predicted rainfall.
We're going to go from drought to a flooded mudfest in a day.
OK, we need the rain. Put on the big plastic rain boots & bring it on.

Posted by: FIREDRAGON47 | September 29, 2010 10:07 AM | Report abuse

Just think if this were snow.....

Posted by: maestrojmk | September 29, 2010 10:13 AM | Report abuse

What's with all the rain on the radar??? You mentioned no morning rain and said there was only a 30-40% of afternoon rain. Radar shows Fairfax County has rain and even heavier rain just a county or two below us moving this way. I left all my windows open since it's cool out. My carpet is gonna be soaked now. Thanks for another forecast fail!

Posted by: rwalker66 | September 29, 2010 10:14 AM | Report abuse

New post up.

Posted by: snowedin85 | September 29, 2010 11:00 AM | Report abuse

Jaybird926,

It would have been helpful if Camden had been more specific in his response to your inquiry.

As Jason noted in his Post blog last night, National Airport is over 7" below normal for the year-to-date. Thus, we will need that much from this storm to eliminate our rainfall deficit for the year. As it stands, over 17" needs to fall over the next 3 months for DCA to simply reach its annual normal precipitation.

Hope this helps!

Posted by: TominMichiganParkDC | September 29, 2010 11:01 AM | Report abuse

@rwalker66

I'm not aware of any reports of rain in the metro area thus far. Could a shower still sneak in before noon? Maybe just barely. The 30-40% chance of afternoon showers means just that -- there could be some afternoon showers. But the precip, as has been evident on radar, will try to dry up a bit as gets closer to the metro area. Thus, showers may be mostly light to moderate and possibly scattered during the afternoon into evening until heavier stuff overnight into tomorrow. -Dan, CWG

Posted by: CapitalWeatherGang | September 29, 2010 11:04 AM | Report abuse

The good news: None of my dances are affected...my next possible dance is Friday evening at the Dulles Hilton, and my usual Tuesday evening Clarendon Ballroom dance on the 5th was bumped for someone's "private event" [Hmmm...wonder who's having a Tuesday evening wedding reception @ the Clarendon Ballroom next week...Katy Perry???].

Now for the bad news...this projected semitropical breezy deluge DOES interfere with some afternoon errands today and tomorrow in Ballston, plus anything for which I have to go outdoors [garbage, laundry, etc.] Let's just hope it doesn't get too bad. Perhaps things will start to taper off by tomorrow afternoon. Unfortunately the rain seems to be starting up this afternoon, though "Nicole" is still near Key West or even in Cuba at present. This system seems to be moving rather rapidly for a south-to-north tropical system near Florida. Normally such a system takes up to three days to affect us up here. I've seen systems [Fran, Floyd, Isabel] which took a full day to get here after striking the Outer Banks.

Posted by: Bombo47jea | September 29, 2010 1:17 PM | Report abuse

Hi CWG. My focus is narrow -- this is less rain than TS Hanna, right? I think my flooding issue is with more than 5" -- it seems we are in the 3-4 inch category? (Hanna was 6-7 if I recall). I would say please tell me I am right, but actually I have work to do tonight if I am wrong.

Posted by: erbele | September 29, 2010 1:39 PM | Report abuse

@erbele

I believe Hanna was on the order of 4-7"+ for the area. We should be looking at less from this, though you can never rule out localized extreme amounts. Take a look at the new post that just went up. May answer some more of your questions.

Posted by: CapitalWeatherGang | September 29, 2010 1:46 PM | Report abuse

The comments to this entry are closed.

 
 
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