Capital Weather Gang - DC area weather blog, news - September 26, 2010

Forecast: Welcome Saturday serenity

How about instead of searing heat or flooding rain, we have some nice, fall weather? Saturday, at least, delivers that to us. Sunday is semi-serene, but clouds increase and some light rain could break out late in the day or at night. Monday looks like another washout, but nothing like what we experienced Thursday. Unsettled, cool weather may persist through Tuesday..

By Jason Samenow | October 2, 2010; 4:55 PM ET | Permalink | Comments (13)
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PM Update: Quiet and cool Friday night

Even though we saw a ton of sun the last few weeks and months and it's nothing unusual, I'm glad it returned in a big way today. After all the rain this week, today is a winner in my book. Highs have reached near 70 and into the low 70s most spots. The main downside is a stiff wind from the northwest that has gusted as high as 30 to 35 mph during the day.

By Ian Livingston | October 1, 2010; 3:30 PM ET | Permalink | Comments (11)
Categories: Forecasts
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Rain review: Took some time to get it right

Nailed the first half. Took several tries on the second half. That basically sums up our forecast performance for Thursday's record rainfall. We correctly warned ahead of time of the likelihood for heavy rain and the potential for flooding. And, for the first wave, we got the timing of heaviest rain right (late Wed. night into midday Thurs.) and essentially the amount. But we did not initially expect the rainfall double whammy in the metro region.

By Jason Samenow | October 1, 2010; 2:30 PM ET | Permalink | Comments (3)
Categories: Weather Checker
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Rainfall records for D.C., Baltimore

After months of mostly dry, it's been quite the wet week. Yesterday, September 30, 2010, Baltimore added another big record to its list for the year -- the one-day rainfall record for the month. The 6.02" of rain that fell at Baltimore-Washington (BWI) in a 24 hour period surpassed the previous Sept. record of 5.97" on Sept. 24, 1912.

By Ian Livingston | October 1, 2010; 10:50 AM ET | Permalink | Comments (15)
Categories: Floods, Local Climate
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Forecast: 'Rainageddon' out, cooler air in

Our tropical deluge -- just the latest extreme weather event in this crazy extreme weather year -- departs today after dumping several inches of rain across the area. It's another rough commute this morning as flooding remains an issue even after the heavy rains have gone. But once we get past today's lingering winds, we have a pretty decent several days in store if you're a fan of fall. Sure, there are a few rain chances along the way. But nothing like the drenching we just saw.

By Camden Walker | October 1, 2010; 5:00 AM ET | Permalink | Comments (45)
Categories: Forecasts
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Torrential rains swamping region

Intense rainfall, with rates as high as 1-2" an hour along the I-95 corridor, is dousing much of the metro region. Storm totals are now in the 3-6" range on average in the immediate metro area, with lamounts exceeding 8" from Baltimore south along the western side of the Bay. An additional 1-3" of rain is possible on top of what has already fallen.

By Jason Samenow | September 30, 2010; 9:45 PM ET | Permalink | Comments (35)
Categories: Floods, Updates
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Second wave of heavy rains advancing north

This isn't over. Another large area of rain extending southeast through North Carolina and into the Atlantic ocean is headed north and taking aim at the metro region. Rain will again overspread the metro region over the next several hours. Based on current radar trends and model guidance, it looks like another 1-2" of rain could fall in inside the beltway, around 1" in the north and west suburbs (with amounts decreasing further north and west of eastern Loudoun and Montgomery counties) and 1-3" in the eastern suburbs. As with this morning's rain, some locally heavier amounts are possible as well as flash flooding.

By Jason Samenow | September 30, 2010; 6:15 PM ET | Permalink | Comments (37)
Categories: Floods, Updates
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Some gusty storms, then possible rain round 2

A band of showers and thunderstorms is moving northeast along a front associated with the first low pressure that passed by this morning. This band may contain some severe weather, with damaging winds the main threat -- and of course the risk of additional flooding with any more rain. Also, winds are a factor this afternoon even where it's not raining, sustained above 15 mph most spots wth gusts near 35-40 mph common.

By Ian Livingston | September 30, 2010; 4:00 PM ET | Permalink | Comments (19)
Categories: Forecasts
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Rain takes a brief breather, flood risk continues

Rain is starting to diminish in coverage and intensity from south to north, after a general 2 to 4.5 inches since last night. The big exception is around the Chesapeake Bay - primarily counties on the west side - where totals have reached 5 to 8 inches and rain continues. Though rain is currently on the decrease in many locations, scattered showers remain likely through the afternoon. More importantly, a second wave -- positioned near the North Carolina/South Carolina coast -- is beginning to surge north. This wave, also rich in deep tropical moisture, may bring another round of torrential rain tonight - particularly along and east of I-95.

By Jason Samenow | September 30, 2010; 2:00 PM ET | Permalink | Comments (22)
Categories: Floods, Updates
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Deluge not done yet, flood risk remains

It's still raining buckets out there, with rain totals to the tune of at least 2-4" for most locations thus far. Locally higher amounts near and over 7" have been reported, especially along the western shore of the Chesapeake Bay, which has been pummeled by a seemingly endless stream of heavy rain and seen a few tornado warnings as well.

By Dan Stillman | September 30, 2010; 12:10 PM ET | Permalink | Comments (20)
Categories: Floods, Updates
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Rainfall mounts, flash flood warning continues

A vast feed of deep tropical moisture extending south of Cuba is shooting up a front draped across the East Coast producing copious rainfall totals across the entire region. Through 9 a.m., generally 1.5-5 inches of rain has fallen across the region, with the highest amounts near the Bay. In the immediate metro area, the highest amounts have been in south central Fairfax county to eastern Prince William county where 2.5-4+" have fallen.

By Jason Samenow | September 30, 2010; 10:55 AM ET | Permalink | Comments (37)
Categories: Floods, Updates
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Flash flood warning extended until 12:30 p.m.

One to three inches (localized amounts to near 4") of rain have already fallen across the metro region this morning. The heaviest rain has fallen from eastern Prince William county into central Fairfax county. At least another 1-3" is on the way as copious tropical moisture streams northward.

By Jason Samenow | September 30, 2010; 9:30 AM ET | Permalink | Comments (17)
Categories: Floods, Updates
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Flash Flood Warning for entire metro region

Torrential rains have prompted the National Weather Service to issue a Flash Flooding Warning for the entire metro region until 10:45 a.m. this morning. Excerpt:

By Jason Samenow | September 30, 2010; 6:20 AM ET | Permalink | Comments (2)
Categories: Alerts, Floods
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Forecast: Soaking, perhaps flooding, tropical rains

Allow plenty of extra time for your commute today as very heavy rain is possible across the area. The morning commute could be quite treacherous with standing water a real concern. Do not attempt to drive through flooded roadways. Once we get through today, ready yourself for a cool air intrusion this weekend with highs mainly in the 60s. Parts of the western exurbs might even dip into the upper 30s by Sunday morning. Some might argue with me, but I think it beats the heck out of days of non-stop 90s!

By David Streit | September 30, 2010; 5:00 AM ET | Permalink | Comments (3)
Categories: Forecasts
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Steady rain moves into metro region

After a long wait, rain has finally enveloped the metro region. Mainly light to moderate rain currently encompasses the area but much heavier rain is streaming north and northwest from the southeast. Just to the east and southeast of Richmond, doppler estimated rainfall has already exceeded 2-2.5" in spots. By 5 a.m. - the time of our next update -- 1"+ amounts will probably extend into the metro region.

By Jason Samenow | September 30, 2010; 1:00 AM ET | Permalink | Comments (3)
Categories: Updates
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The calm before the rainstorm

After some showers in the afternoon, we have a brief in the lull in the rain - auspiciously timed to allow the final home game at Nationals Park this evening. But a massive shield of rain fed by moisture deep into the tropics (cool water vapor loop) lurks to the south. We're sticking with our prediction for a general 2-4" rainfall event (with some locally higher amounts), but NOAA's Hydrometeorological Prediction Center is a little more aggressive: forecasting 3-6" (with some potential for 6-10" totals). The heaviest rain is expected between about 4 a.m and 10 a.m.

By Jason Samenow | September 29, 2010; 8:30 PM ET | Permalink | Comments (32)
Categories: Floods, Tropical Weather, Updates
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Tropical storm Nicole is no more

The bottom line here is that Nicole is dead but the incredible stream of moisture from the tropics that fed Nicole is being funneled into new low pressure that will spread very heavy rain over much of the mid-Atlantic and Northeast over the next couple days.

By Jason Samenow | September 29, 2010; 6:00 PM ET | Permalink | Comments (9)
Categories: Tropical Weather
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PM Update: Rain underway, much more to come

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.

By Ian Livingston | September 29, 2010; 4:05 PM ET | Permalink | Comments (19)
Categories: Forecasts
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NOAA: Rainfall may be "very dangerous"

NOAA's Hydrometeorological Prediction Center is sounding the alarm bells about possible flooding in the mid-Atlantic, including the entire D.C. metro region. In its "Excessive Rainfall Discussion" released at 2:41 p.m., it warned: ...VERY DANGEROUS EXCESSIVE RAINFALL/FLASH FLOOD EVENT FOR THE MID-ATLANTIC INTO NORTHEASTERN U.S... and cautioned: ...SETUP IS SOMEWHAT SIMILAR TO THE JUNE 26-29...2006 HEAVY RAINFALL EVENT...

By Jason Samenow | September 29, 2010; 3:11 PM ET | Permalink | Comments (11)
Categories: Floods
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Moisture from tropics to feed D.C. rainmaker

By the time tropical storm Nicole nears the mid-Atlantic coast, it will have transitioned into an entirely different kind of weather-maker more closely resembling a 'Noreaster than a tropical storm. Though the track of Nicole itself is now forecast to pass to mainly east of Washington, its deep plume of moisture will be feeding a new low pressure system riding up a cold front draped across the interior mid-Atlantic. The end result will be generous rainfall amounts with localized flooding and some gusty, but not likely damaging winds.

By Jason Samenow | September 29, 2010; 1:30 PM ET | Permalink | Comments (22)
Categories: Floods, Tropical Weather
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Tropical storm Nicole not so tropical

Tropical depression 16 (TD16) - though very close to tropical storm status - has thus far failed to intensify since forming yesterday in the Caribbean Sea, a little more than 100 miles south of Havana Cuba. The center of circulation is believed to be located roughly 230 miles south-southwest of Miami, Fl. TD16's maximum sustained winds are now estimated at 35 mph, four shy of what it needs to be named tropical storm Nicole. The poorly organized circulation is expected to continue a NNE movement at roughly 10 mph for the next day or so, with an increase in forward speed thereafter. Tropical storm warnings are posted for southeast Florida, where essentially a rainy and only modestly windy event is expected. The strongest winds and most intense thunderstorm activity are dislocated from the center by several hundred miles to the southeast. From our distant glance, it's difficult to identify classic features of a tropical cyclone.

By Greg Postel | September 29, 2010; 11:00 AM ET | Permalink | Comments (21)
Categories: Tropical Weather
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Forecast: Heavy rain takes aim on D.C. area

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.

By Dan Stillman | September 29, 2010; 5:00 AM ET | Permalink | Comments (24)
Categories: Forecasts
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NatCast: Rain threatens last home game of season

ine-height:15px;padding-left:18px;padding-right:18px;margin-top:8px;font-weight:normal">The steady and possibly heavy rain is coming at some point this afternoon or tonight, but it's hard to say exactly when. Which means all hope is not lost for getting this game in. Keep an eye on radar and check back for an update later in the day. If this turns out to be the season's last NatCast, then so long and we'll see ya next year.

By Dan Stillman | September 29, 2010; 5:00 AM ET | Permalink | Comments (8)
Categories: NatCast
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Tropical depression tracks aiming at metro region

Many of the latest track forecasts for Tropical Depression 16 (TD16), likely to strengthen to tropical storm Nicole tonight or tomorrow, have converged over the D.C. metro region. Although it is still quite likely that these forecasts will shift around some more, a heavy rain event for the metro region late Wednesday night into Thursday seems increasingly likely.

By Jason Samenow | September 28, 2010; 8:30 PM ET | Permalink | Comments (23)
Categories: Local Climate
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PM Update: Brief respite in stormy period

Since a cold front went through this morning, dew points have been steadily falling and the very muggy air mass of yesterday is gone for now. Under partly-to-mostly cloudy skies this afternoon, temperatures are rising to highs in the upper 70s and lower 80s across the area. Our break, and more pleasant conditions contained within it, won't last too long.

By Ian Livingston | September 28, 2010; 3:15 PM ET | Permalink | Comments (11)
Categories: Forecasts
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Tropical depression forms, eyes Florida, East Coast

A vigorous disturbance swirling in the Caribbean south of Cuba was classified a tropical depression late this morning by the National Hurricane Center. The depression (TD16), the 16th of the season in the Atlantic basin, will be named tropical storm Nicole if it strengthens as forecast later today. Tropical storm warnings (map) have been posted for much of South Florida, the Florida Keys, the Cayman islands, Cuba, and the northwest and central Bahamas. After passing south Florida tomorrow, this system is then likely to race up the East Coast, potentially impacting large areas with wind and flooding rain - including the D.C. metro region.

By Jason Samenow | September 28, 2010; 12:45 PM ET | Permalink | Comments (30)
Categories: Floods, Tropical Weather
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The rain that wasn't

It doesn't happen that often, but - once in a great while - we miss a forecast. Badly. CWG's predicted rain totals of 1-3", with isolated higher amounts didn't come close to verifying in many locations. The National Weather Service's forecast of 2-4" with isolated amounts over 5" fared even worse.

By Jason Samenow | September 28, 2010; 10:45 AM ET | Permalink | Comments (14)
Categories: Floods, Weather Checker
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Forecast: Showers to wind down, afternoon sun

After a mostly calm and quite warm September, we have been seemingly catapulted into a much more volatile, transitional weather situation. From our previous dryness standpoint, this is a good thing as we'll see frequent chances of precipitation. But from a daily outdoor planning angle, this creates complexity that challenges our confidence at times. In the coming days, we'll see the weather change quickly from one half of the day to the next.

By Matt Rogers | September 28, 2010; 5:00 AM ET | Permalink | Comments (14)
Categories: Forecasts
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Natcast: Nice weather window

* Our Full Forecast | Weather Wall | Nationals Journal * Nationals vs. PhilliesToday, 7:05 p.m., Nationals Park First Pitch9th InningWeatherChance of Rain7670Partly to mostly clear skies5%Game weather looks very nice tonight and a welcome reprieve from recent wetness NatCast appears on the day of every Nationals home game....

By Matt Rogers | September 28, 2010; 5:00 AM ET | Permalink | Comments (0)
Categories: NatCast
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PM Update: Periods of storminess into the night

It's pretty muggy out there today and when you mix in a lot of atmospheric action above the surface, we're under the risk of some heavy rain and even isolated severe thunderstorms. So far, the action today has been rather scattered and that may continue, but many spots have seen at least periods of heavy rain and by the time this is all done, 1-3" of rain is likely in most spots, with isolated 3-5" amounts.

By Ian Livingston | September 27, 2010; 3:30 PM ET | Permalink | Comments (28)
Categories: Forecasts
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Flood warning for E Montgomery and W Howard Co

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A FLASH FLOOD WARNING FOR WESTERN HOWARD COUNTY IN CENTRAL MARYLAND [AND] EASTERN MONTGOMERY COUNTY IN CENTRAL MARYLAND...

By Jason Samenow | September 27, 2010; 2:55 PM ET | Permalink | Comments (5)
Categories: Floods
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Tornado risk: why today's storms may spin

There is an elevated tornado risk today into tonight and tornado warnings have already been issued in the Maryland suburbs. What's the cause? It turns out there is an unusual amount of spin in the atmosphere due to changing winds in different layers of the atmosphere above us.

By Jason Samenow | September 27, 2010; 1:00 PM ET | Permalink | Comments (3)
Categories: Thunderstorms
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Tornado warning for Howard Co. until 12:45 p.m.

TORNADO WARNING FOR CENTRAL HOWARD COUNTY IN CENTRAL MARYLAND UNTIL 1245 PM EDT

By Jason Samenow | September 27, 2010; 12:04 PM ET | Permalink | Comments (7)
Categories: Alerts
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Hefty rainfall totals possible through tomorrow

During all of September, the region has received just 0.81" of rain through yesterday, 2.5" below average. Though the immediate metro region is not officially in "drought", the U.S. Drought Monitor does state the region is "abnormally dry". Parts of western Virginia and western Maryland are officially designated drought areas, with isolated locations in severe drought. Much of the region may make up at least the September portion of the current rainfall deficit in the next 24 hours, with 1-3" of rain forecast.

By Jason Samenow | September 27, 2010; 11:00 AM ET | Permalink | Comments (8)
Categories: Floods
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Forecast: A soaking, stormy start to week

Rain has been hard to come by over the last four to six weeks but a moisture-laden southern storm changes all of that over the next two days. Bands of showers and thunderstorms, sometimes heavy, pivot through the region through tomorrow morning, potentially producing up to 2 or 3 inches of rain. There's a slight chance of more rain Thursday into Friday before our first real taste of cool fall air settles in for the weekend.

By Jason Samenow | September 27, 2010; 5:00 AM ET | Permalink | Comments (8)
Categories: Forecasts
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NatCast: Rain likely, but how heavy & when?

Showers are likely and possibly thunderstorms. It's possible that the heavier rain holds off long enough to the get the game underway. But there's a decent chance of a delay, postponement or shortened game at some point.

By Jason Samenow | September 27, 2010; 5:00 AM ET | Permalink | Comments (5)
Categories: NatCast
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Forecast: Bye-bye heat wave, hello rain clouds

Today brings a rather abrupt change in the weather regime. Warm winds from south and southwest are replaced by cool winds from the north and northeast and some showers. The end result is temperatures 20 to 30 degrees below levels reached yesterday and Friday. Intermittent rain continues possible through Tuesday. We'll have to carefully monitor conditions late Monday into Tuesday as instability and spin in the atmosphere may trigger some severe thunderstorms.

By Jason Samenow | September 26, 2010; 4:15 PM ET | Permalink | Comments (39)
Categories: Forecasts
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NatCast: Cloudy and cool; showers?

* Our Full Forecast | Weather Wall | Nationals Journal * updated at 9:15 a.m. Nationals vs. BravesSunday Sept. 26, 1:35 p.m., Nationals Park First Pitch9th InningWeatherChance of Rain70-7268-70Mostly cloudy25%Temperature-wise, a much more comfortable afternoon for baseball viewing compared to yesterday. There is a chance of showers, though they would...

By Jason Samenow | September 26, 2010; 5:00 AM ET | Permalink | Comments (0)
Categories: NatCast
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Capital Weather Gang: September 26, 2010 - October 2, 2010