East Coast storm: Flash flood warning, tornado warning, heavy rain

Sep 30, 2010

Capital Weather Gang chief meteorologist Jason Samenow will be online Thursday, Sept. 30, at 10 a.m. ET to discuss the latest weather inclujding flash flood warnings and tornado watches for the Washington metro region.

Latest from the Capital Weather Gang

An incredible moisture feed from the tropical Caribbean is streaming up the East Coast producing copious rainfall amounts.  Rainfall totals in the D.C. metro region are generally range from 1.5-5" so far with the highest amounts near the Bay and in south central Fairfax and eastern Prince William counties.  Flash flood warnings are in effect.

Several tornado warnings have been issued for locations near the Bay in Anne Arundel, Calvert and St. Mary's county.  A tornado watch remains in effect for DC and points east through 1 p.m.

Happy to take your questions.

I'm seeing lots of conflicting reports about what the rain will be doing between after 2. What are the chances the rain will be done by then, or at least just drizzly?

Yesterday, it looked as if the rain might cutoff by mid-afternoon, but the latest data indicate rain -- heavy at times -- could continue into tonight - prolonging the flooding threat.

Leaving around 6:30 this evening. What kind of weather will we encounter?

You may run into some heavy rains and gusty winds along the Eastern shore this evening.  The National Weather Service is calling for wind gusts as high as 50 mph there.  High surf and minor coastal flooding is also likely.

...or has this year had more extreme weather than past? One or two incidents (i.e. one snowstorm, extended heat wave, drought, tropical storm remnants) would seem normal, but this many has been hard to bear.

There's no doubt this has been an unusually busy and extreme weather year.  From the record snowy winter to the record hot summer to now this extreme rain event, we've certainly had our hands full.  Hot summers -- like we just experienced -- may become more common in the future due to global warming.

First of all, will my plane get off the tarmac at BWI? Second, will it be able to land, or does this storm peter out as it goes north or as I move away from the ocean?

This storm is vast and impacting much of the mid-Atlantic and Northeast with wind and torrential rain.  I would expect flight delays up and down the East Coast today.  Hard to say what will happen with an individual flight.

What are the chances for widespread power outages here in D.C.? Should I be keeping my fingers crossed for an afternoon off of work?

I'm not expecting widespread power outages in the immediate metro area. Winds will only be 10-20 mph or so -- with perhaps some modestly higher gusts in heavy rain bands.

Near the Chesapeake Bay there is a slightly better chance -- especially if tornadoes touchdown (there have been warnings in Calvert, St. Mary's and Anne Arundel counties).  And also in the vicinity of the Va./Md./De. beaches which  could see gales and gusts over 50 mph .  But even in these locations, outages probably would be isolated, not widespread.

Try to cross the Bay Bridge in the daylight . Gale force winds on the bridge no fun along with the heavy rain. It can be quite an adventure getting across depending on your vehicle.

Good point.  I've never experienced this myself, but have heard horror stories.

at National Naval Medical Center in 1959. This [is the] way summers used to be, etc. Nothing unusual and please do not blame global warming.

Average temperatures have warmed since the 1950s.  The data clear indicate that.

When do you see the largest amount of rain ending in the Wash Metro area?

This is a really tough question.  Rain -- heavy at times - should continue into the early afternoon.  There may be a break or lull at some point -- with coverage and intensity diminish as you go west of DC.  From DC and points east, however, the chance of a break is lower -- and another batch of heavy rain could even come through tonight.

Going camping this weekend in Shenandoah - how muddy should we expect our campsites to be?

The good news is that it dries out a bit tomorrow -- with a considerable sunshine in the Shenandoah.  That should prevent it from being a total mudfest.  The weekend looks nice'n dry.

Was in the remants of a Tropical Storm. 50mph gusts+ and roads to Bethany were flooded. That was 25 years ago. I still remember it vividly. Original poster should really leave in the daylight. Not that unusual that the roads near Bethany and Rehobeth flood in large stretches.

Great advice.  This is a serious East Coast storm and caution should be exercised.

Seven feet of snow, no rain for three months, now floods! This is all because the Redskins blew two early leads and God is angry with Washington!

If the Redskins performance is the barometer for weather, I fear protracted weather misery.

how much snow would it be?

On average, 1" of rain is equivalent to 10" of snow... so this would be 30-60" of snow or more.  But in winter, we never have this kind of deep tropical moisture feed, so those amounts would never occur.

My house is covered in those little critters. Will they drown?

I'm afraid the rain might push the stink bugs to take refuge inside.  I really hope not though.

Watching the radar, this storm appears to be a fast mover (it's just a large moisture area) - is that the case or am I just reading the radar maps incorrectly. If this storm was to hit during the winter time, how much snow would we get?

While this is a fast moving storm, the feed of moisture is really, really long -- all the way south of Cuba.  So we may get an additional wave tonight after the wave today passes -- but the exact track of the second wave isn't clear (probably more impacting DC and points east, rather than west).

Is it just me or does it smell like a day at the beach outside? Is it possible that the rain actually has sea water mixed up with it?

Though the salinity is mixed out of the rain, this storm is being fed by abundant Atlantic moisture.  The rain bands we're getting  originated over the ocean.

For what it's worth, I'm at my office in Albany, where it is raining. We're being told same as you guys down there - rain, heavy at times, wind, heavy at times, etc. etc. etc. Also, flood watch. Wheee!

This storm is remarkable in its north-south extent.  Thanks for the report.

I keep hearing 2-5" of rain, but nobody seems to know for sure. If we get say 4" of rain, where does that put us total wise for the year? Seems like it didn't rain for months.

Before yesterday we were 2.5" below average for the month.  I'm confident we'll erase that deficit with this storm.  National has already received more than 2".   I think the total there will be in the 3-6" in rain -- cutting the annual deficit of just over 7" in half, at least.

I have lived in this area since I was born at Johns Hopkins in 1948 and this was by far the hottest summer I can remember--it was instructive in showing us the dramatic difference between a 90 degree day a 100 degree day; a much bigger difference to the human body than that between 80 and 90. Also, while I remember two major snowfalls in the winter of 1959 (my mother had to cook over wood in the fireplace due to power outages) we never had two full on blizzards in the space of of a week as we did this past winter. The anomalies are too vivid to ignore.

Thanks for the comment. Long term temperatures show an increase but average snowfall has declined -- even when you factor in 2010's remarkable winter.  There's high confidence global warming will increase temperatures.  What it will do to snowfall is a more complex question.

Really enjoyed the chat.  A severe thunderstorm warning is in effect for northeast D.C., eastern Montgomery and northern PG counties for heavy rain and the potential for damaging wind.  And, the flash flood warning has been extending until 4:30 p.m.  Be careful today and remember do not attempt to cross a flooded roadway.  Turn around, don't drown.

Stay tuned to the Capital Weather Gang blog and follow us on Twitter (@capitalweather) for updates throughout the storm.

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Jason Samenow
Jason Samenow is chief meteorologist with the Capital Weataher Gang.
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