From the ABC 7 Weather team

DC Fall Foliage Season Just Around The Corner

September 21, 2014 - 07:24 PM
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A wet September and October is ideal for bright fall colors. On the contrary, a drier than average late summer and early fall accelerates the leaf-changing process and the leaves tend to fall before the best color can be reached.

In Washington, while the year has been wetter than average, September has been mostly dry. Rainfall deficits are 2.0 to 2.50 inches inside the Capital Beltway. Central Virginia is also a bit drier than average with rainfall deficits around 2.50 inches as well. The Interstate 81 is in better shape with Hagerstown, Md., and Martinsburg, W.Va., in a 0.80 to 1.10 inch deficit.

Therefore, the dry trend does not bode well for an exquisite outbreak of luscious colors. Looking ahead, the upcoming pattern doesn’t favor rain until the end of the month.

What else helps to create deep oranges and yellows, etc., in the fall foliage? Warm, sunny days followed by crisp, cool nights with temperatures above freezing. Therefore, high temperatures in the 60s and 70s with lows in the middle 30s to around 50 degrees.

peak fall foliage

The sharp temperature changes keeps sugars from reaching the leaf’s root system so the sugars are converted into pigments that produce the brilliant colors.

The upcoming pattern, while dry, favors a nice swing in temperatures with highs in the 70s and lows in the 50s. This trend is also right on par with climatological averages in the nation’s capital. A biting frost or early hard freeze is not on the near horizon in the western suburbs, which will help bring out the wonderful colors.

Frequent rain and wind events in the fall will bring the leaves down before they reach peak color as well.

peak fall foliage

So, while the month will likely end drier than average, the soggy summer will hopefully pull through and the favorable temperature trend could be the icing on the cake to a picturesque fall!

Here’s a look at when fall colors typically peak in the region; the colors first appear in the Alleghenies by early October and then the foliage season migrates into the District by Halloween. The eastern shore is the last to see the best colors; here it’s usually a few weeks prior to Thanksgiving.

peak fall foliage

Want to know the full process of how the leaves change color? Check out this detailed fall foliage blog by Alex Liggitt on the transformation the leaves go through to become vibrant in the fall.

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Only A Few Days of Summer Left Before Autumn Begins

September 19, 2014 - 02:19 PM
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Enjoy this last weekend of summer - because it is going to feel more like summer here in the Washington D.C. area! Temperatures throughout this last week of summer have been running below normal giving us a little taste of Fall.  However, by the time we head into this weekend, temperatures will top out in the 80s for much of the region thanks to high pressure clearing out cloud cover and helping us boost into the 80s with a light southeasterly flow.

A cold front will cross the area Sunday which will give way to some clouds and about a 30% chance of showers in the afternoon and evening hours moving from west to east. This cold front will also sweep away any of the summer-like weather we have left and leave us with another spell of Autumn weather around the region.

This is happening right in time because the autumnal equinox arrives at 10:29 p.m. on Monday! People celebrate this moment across the world and really the precise moment is when the sun passes directly over the equator! This happens twice a year as you may recall (the "spring equinox" and the "autumnal equinox"). 

 

ZZZZZ

 

In latin, the word "equinox" means "equal night" --"equi" meaning "equal" and "nox" meaning "night". This signifies the equal parts of daylight and darkness.

However, this is not always so "matter-of-fact." The sunrise on Monday is 6:55 a.m. and the sunset is 7:07 p.m. This isn't exactly equal. In fact, we have to wait until Tuesday, the first full day of Autumn to get the full equal light-equal night. The sunrise on Tuesday is 6:56 a.m. and the sunset is 7:06 p.m.

My colleague Eileen Whelan summed it up correctly when she wrote:

"We have the atmosphere to thank for this oddity. Also, the definition of sunrise and sunset. Sunrise occurs the moment the tip of the sun can be seen on the horizon and sunset is the last minute the sun can be seen before it dips below the horizon. Also, keep in mind our atmosphere refracts, or bends, light, which makes it appear as if the sun is rising or setting earlier.

The true equinox occurs when the center of the sun's disk crosses the celestial equator and this occurs at 10:29 p.m. EDT on Monday, September 22. At the same time the equinox occurs in D.C., it occurs across the globe."

Either way, you won't notice a different from Monday to Tuesday, from Summer to Autumn. However, you will notice that the hours of daylight start getting shorter until the Winter Solstice which begins on December 21, 6:03 P.M. EST (which is also the darkest day of the year meaning the day with the least amount of daylight.

However, as we make the transition into Fall, it may seem a little cooler according the outlook by the Climate Prediction Center:

 

ZZZZZ

But, also according to the Climate Prediction Center for the 8-14 day outlook, temperatures may be a little on the warmer side!

 

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So don't pack away those flip-flops yet for those boots. Fall is here to stay but bouts of summer may stick around until early October!

 

 

 

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Hurricane Isabel: 11 years later

September 19, 2014 - 05:00 AM
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Isabel made landfall along the Mid-Atlantic on Sept. 18, 2003. Photo: NOAA

Many of us remember enduring days - some weeks - without power. Flooding and downed trees and power lines were just some of the hardships faced after Isabel slammed into the East Coast on Sept. 18, 2004.

NOAA

Hurricane Isabel has gone into the record books as one of the most significant tropical cyclones to affect the Chesapeake Bay area since Hurricane Hazel in 1954 and the Chesapeake-Potomac hurricane of 1933.  Here are a images of Isabel's impact in our area.

Isabel Damage
Isabel Damage
Isabel Damage in Calvert County, MD

Isabel was the ninth named storm of the 2003 Atlantic hurricane season. It originated about 625 miles west of the Cape Verde Islands on Sept. 6, 2003. The storm tracked westward, gaining intensity and, at one point, reached Category 5 status with maximum estimated sustained winds around 165 mph. Check out Isabel's track:

NOAA

By the time Isabel made landfall near Drum Point, N.C. around midday Sept. 18, it was still a Category 2 hurricane with maximum sustained winds of 105 mph.

Isabel then tracked north-northwest, losing tropical characteristics, but still producing flooding rain and tropical storm force winds. Here's an image of the radar, as the center of Isabel tracked over North Carolina.

Wakefield, VA NWS

The copious amounts of rain, coupled with strong winds, tore down trees and power lines and even led to a few fatalities.

Locally, the Shenandoah Valley received 6-12 inches of rain. Between two and six inches of rain fell in western Maryland and eastern West Virginia, and the Baltimore/Washington region received a total of one to three inches of rain.

At the height of the storm, Reagan National recorded a wind gust of 50 mph.

NOAA

Unusually high storm surge accompanied the storm with some watersheds between six and feet above normal. The storm surge in the Chesapeake Bay and Potomac River reached the highest levels since the Chesapeake/Potomac hurricane of 1933.

USGS - http://md.water.usgs.gov/publications/press_release/2003/2003-10/

From emergency management reports, estimates of about 6 million customers lost power at some point during the storm in North Carolina, Virginia, Delaware, West Virginia, Pennsylvania, and Washington, D.C.

The estimated total economic loss from Isabel was about $5 billion, according to the American Reinsurance Group. With so many people affected by the tropical cyclone, it took a long while to fully recover.

Even with the advanced warning of the hurricane, thousands of people were impacted by Isabel.

Further information about Isabel is available from the National Hurricane Center, National Centers for Environmental Prediction, United States Geological Survey and the National Weather Service.

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Dry start to September in the D.C. area, dry outlook ahead

September 16, 2014 - 12:06 PM
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Over the past few weeks, a few locations saw some moderate to heavy rainfall from storms but they were highly localized. Here are some of the locations that have seen decent rainfall this month on our WeatherBug Network.

Monthly Rain and temps as of Noon Tuesday on our WeatherBug Network

Other parts of the area haven't been quite as lucky as of late, with official reports at the local observation stations capturing relatively little rain for the month of September. Officially, precipitation totals so far this month are running anywhere from 1" to 1.5" below normal. Unfortunately, the current outlook isn't going to bring appreciable rainfall anytime soon.

Rainfall by the numbers this month and for the year

Above is a look at how the region is faring as far as precipitation this September. Dulles Airport is struggling the most, with only 0.21" of rain in the first 16 days. The observation station is running over an inch and a half below average for the month.

BWI Marshall has been the closest to average precipitation but is still running around an inch below for the month.

Maryland Drought Monitor

As far as the drought monitor is concerned, the region isn't even abnormally dry. This may change over the next week or two, but looking at the statistics for Virginia and Maryland, there aren't any regions with drought in Maryland and only a few abnormally dry spots south of D.C. in Virginia.

Virginia Drought Monitor

Much of this is due to the fact that the region has such a big surplus for the year and stayed around normal over the summer months. Precipitation is still running nearly 6 inches above average for the year at Reagan National and over 9 inches above average at BWI Marshall.

QPF today through next Tuesday morning from the WPC

The forecast looking ahead over the next few weeks doesn't look to good for rainfall chances in the D.C. area. The WPC forecast above only brings about a chance for light rain over the next week, and other modeling continues to depict dry conditions even through next week. A few showers may be possible with a cold front next Monday into Tuesday, but beyond that the region may not see decent rainfall until after the following weekend of the 27th and 28th. We'll of course keep you up to date with our latest 7-Day Forecast.

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Sunday Night "Mysterious Flash of Light" in the Sky

September 15, 2014 - 07:53 AM
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Many reports have been coming in of people in the D.C. region seeing a bright flash in the sky last night. It happened just before 11 p.m. Eastern Daylight Time. Most reports on the American Meteor Society website are described as a bright white or yellow flash that lasted around one second. Here is a map of all of the reports:

(Meteor Sightings via American Meteor Society)

So, what was it? Most likely, it was a meteor. Meteors are pieces of rock, ice and dust, usually from a comet, that explode and burn up as they enter the Earth's atmosphere. There are two meteor showers taking place in the month of September. First, the Southern Taurids, which are active for two months from Sept. 7-Nov. 19th. According to the American Meteor Society, they tend to produce few "shooting stars" but can be rich in fireballs and often responsible for an uptick in fireball reports to the society's website. In addition to the Southern Taurids, the less known Piscids will be near their peak in September and continue through October.  Check out this article from In-The-Sky.org. Let us know if you saw anything: Just go to our Stormwatch7 Facebook page and leave a note. 

Update:

This video was taken from Jesse Ferrell who works for Accuweather in State College, PA. You can see how the fireball completely lit up the night sky.

Here's another look at the meteor from Jeremy Settle, Assistant News Director at News 12 in New Jersey.

 

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Roller coaster temperatures this week, strong storms possible Thursday

September 9, 2014 - 08:46 AM
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The weather picture is rather complex this week and we've got a little bit of almost everything in the forecast, even SNOW! (Ok, the snow is for Canada, Montana and maybe the Western High Plains, but now I have your attention!)

Low pressure has been keeping us cloudy and cool in the Mid-Atlantic since Sunday night. The high in D.C. yesterday was 77 degrees and with mid-upper 70s again today, it will be the coolest stretch of temperatures since late May (thanks to Ryan Miller for that nugget). All of this is happening on the average last date of 90 degrees at Reagan National.

 

(This Afternoon)

 

As the low pressure system departs tonight, our focus turns to a potent cold front that is currently in the Midwest.  MUCH cooler air is coming in from Canada behind it where they have been seeing some snow!

 

(GFS Model showing possible snow in Western NE Thursday)

 

The cold front drops through the plains and spreads toward the east. Check out the chilly nights ahead for our friends to the north!

(Flirting with Freezing Thursday AM Midwest)

Notice on that forecast model that as the cool air invades the nation's mid-section, warm air will be drawn in ahead of that front it the east. It will be muggy in D.C. Wednesday as it warms up to around 80 and by Thursday we reach the top of the roller coaster with  highs back in the mid to upper 80s. Here's a look at highs from the North American Model.

 

(NAM Temperatures Thursday)

 

By the time it arrives in the D.C. area, this storm system will already have a history of producing severe weather. Today it will hit the Midwest and then the Great Lakes/Ohio Valley on Wednesday. By the time it reaches us, much of the energy will be to the north. However, with a strong jet in the upper levels of the atmosphere, the thunderstorms that develop over the D.C. region could produce damaging winds Thursday afternoon/evening. 

 

(Storm Prediction Center Severe Outlook Thursday)

 

This all should pass us overnight on Thursday and stall in the southeastern U.S. That puts us in the cool sector with 70s again for highs and overnight lows in the 50s even inside the beltway. The core of the cool air evades us, but it sure will feel like fall. In addition, a reinforcing cold front comes in on Saturday (bottom of roller coaster) with a few showers. Expect below average temperatures into next week.

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Shelf Clouds Common Prior to DC Storms Lately

September 7, 2014 - 07:58 PM
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Many social media sites have spotlighted these saw-like storm clouds. Just this past weekend, a north to south line of storms produced a long shelf cloud as it hurled from the Cumberland Valley to the nation’s capital.

What does it look like? The image below shows the low, horizontal wedge-shaped cloud. It forms along the leading edge of a thunderstorm’s gust front.

shelf cloud

To understand a gust front, consider the mechanisms in play in a storm. In a thunderstorm downdraft, heavy rain forces the cool air in the atmosphere’s upper-levels to spread to the ground. The air then fans out in all directions once it reaches the surface (since air can’t exactly dig into the ground). The leading edge of this cool air outflow ahead of the storm is called the storm’s gust front.

Shelf cloud 2

Where the gust front meets the warm air ahead of the storm, the air rises and forms shelf clouds. Immediately in the shelf cloud’s wake is where the heaviest rain and strongest winds can be found (such as shown in the image below from the storm that moved through Hagerstown, Md., on Saturday). Shelf clouds are found a few miles ahead of the actual storm.

Shelf cloud 2

Now, shelf clouds don’t precede every thunderstorm. Typically, they are found ahead of thunderstorms that form ahead of a vigorous cold front (like Saturday’s front), an upper-level low pressure or along the leading edge of a derecho. The more powerful the cold front or upper-level disturbance triggering the storm, the better opportunity to see this cloud feature.

So, the next time you see a shelf cloud, remember that often the worst weather is just in its wake. The milky color behind the shelf feature is the heavy rain shaft accompanying the thunderstorm.

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Coastal System Brings Clouds and Showers To Start the Week

September 7, 2014 - 05:07 PM
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Wow!  What a difference a day makes!  An absolutely gorgeous Sunday follows a hot, steamy, and stormy Saturday.  The cold front that slid through late Saturday night has now stalled off the coast.   That has kept the Carolinas rather warm and wet today, but has allowed much drier and cooler air to greet us in the mid-Atlantic and Northeast. 

Along the front, an area of low pressure will develop along the eastern Carolinas.  That will set the stage for an unsettled start the work week.  Cloudy skies will greet us Monday morning with a few sprinkles around.  With the clouds, and an easterly breeze, temperatures will only climb into the mid to upper 70s.  Here are forecast highs for Monday:

Showers will be sporadic, but it will be good to have the umbrella with you with rain chances possible through Tuesday night.  There is also some discrepancy between the model guidance.  The European model favors heavy rainfall Tuesday morning at 8 am along and east of the I-95 corridor, whereas the NAM has only a few sprinkles around.  See the difference in the snapshots below:

WeatherBell European Model 8am Tuesday
WeatherBell NAM Model 8am Tuesday

Folks along the coast will see the heaviest rain and strongest winds.  The Weather Prediction Center's Qualitative Precipitation Forecast (QPF) delineates the highest rainfall totals to be over the eastern shore of Maryland and VA Beach region through the day Tuesday.

NOAA Weather Prediction Center

One thing is for sure, it won't be a bright and sunny start to the week.  The weather pattern changes by Wednesday, as sunshine and more seasonable temperatures return.  Another strong cold front will slide through by week's end bringing another taste of fall to the air by next weekend. 

 

 

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Strong Storms Likely Saturday

September 5, 2014 - 08:19 PM
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It says September on the calendar, but it certainly doesn't feel like meteorological fall.  Temperatures have started out well above average for the first few days of the month, but big time changes are on the way!

A strong cold front is currently moving through the Midwest.  Ahead of the front, very hot and humid conditions exist.  Behind the front, much cooler and drier air.

Strong storms have been firing up along the front all day.  Tomorrow, as the front approaches the east coast, scattered strong and severe thunderstorms will develop.  It'll feel like summer tomorrow afternoon with highs back into the lower 90s, but feeling like the upper 90s with very high humidity.  The heat and humidity, combined with the approaching front, will trigger strong to possibly severe thunderstorms.  The greatest threat from the storms will be damaging winds.  As far as the timing, storms could pop anytime after 2pm.  Here's one simulation at 2pm showing a few storms firing up.

WeatherBell - NAM 2pm

A few other simulations suggest the storms will arrive after 6pm.  Check out our in-house computer model that shows widely scattered showers and storms around at 9pm.

Since it will be so hot and humid, you'll want to keep an eye to the sky for ominous looking clouds.  Storms could fire up at any time.  If you're planning on being outdoors, make sure you have the StormWatch weather app downloaded to your phone for radar updates, as well as dangerous storm warning alerts based on your location.  The greatest risk for storms will be between 2pm and 10pm Saturday.

The rain should wrap up overnight Saturday from NW to SE, as the drier air slowly filters in.  Humidity levels will be noticeably lower Sunday with highs around 80 degrees.  Check out a comparison of dewpoint temperatures (measure of humidity/moisture) Saturday and Sunday.

WeatherBell - EURO 2pm Saturday dewpoint temperature
WEatherBell - EURO 2pm Sunday dewpoint temperature

Saturday afternoon dewpoints will be in the lower 70s compared to upper 40 lower 50 degree dewpoint temperatures by Sunday afternoon. 

The front will stall off the coast Sunday and will keep temperatures slightly below average for the early part of next week.  We'll have to watch the front closely because an area of low pressure may develop along the front and could bring a few showers by Tuesday.  It's still too early to tell, but one thing is certain -- cooler and drier, more September-like, weather will return by the end of the weekend! 

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StormWatch 7 blog: Daylight disappearing quickly in D.C.

September 4, 2014 - 10:45 AM
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I've been talking to a lot of people lately that have noticed just how quickly the D.C. area has been losing daylight. In August alone, the area lost over an hour of daylight, from fourteen hours and ten minutes on the 1st all the way back to thirteen hours and four minutes on the 31st. Take a look at the graphic below, which will give you a good idea of the big milestones coming up.

(Duration of Daylight in D.C.)

So far D.C. has lost two hours of daylight since the solstice, but that will jump to over three hours lost by the end of September. Unfortunately the area will be below twelve hours of daylight by then as well. We'll have to wait until October 20th for eleven hours of daylight, and November 17th for ten hours of daylight.

To find the duration of daylight for D.C. or anywhere in the U.S., go to this site here and go to form A, or look around the world in form B.

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Lapse of the thunderstorms moving through Frederick, MD Tuesday

September 2, 2014 - 06:18 PM
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After seeing the potent line of storms form west of the mountains moving east towards D.C., we quickly scrambled to get all of the necessary information out before clicking a few buttons to record a time lapse! Check it out here.

Did you happen to see it? If you did and took any pictures or video, feel free to share them to our Stormwatch 7 Facebook page!

Here is a great picture sent in from Renee Rohwer from Mount Airy, MD this afternoon.

Shelf Cloud in Mt. Airy, MD from Renee Rohwer

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Severe Thunderstorm Watch until 10pm Tuesday

September 2, 2014 - 04:49 PM
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DOPPLER RADAR  |  HD CAMERAS

Numerous thunderstorms have developed across the region and some of them have become strong to severe. This prompted the Storm Prediction Center and National Weather Service to post a Severe Thunderstorm Watch for the D.C. Metro and points north until 10pm.

Severe Thunderstorm Watch until 10pm

Storms will have the potential for damaging wind, large hail, heavy rain and frequent lightning. Stay tuned to ABC 7 News for the latest updates and please follow @SteveRudinABC7, @alexliggitt and @DevonLucie for updates on twitter.

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Hottest stretch so far this year looks to continue into September

September 1, 2014 - 08:16 PM
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After a hot end to August, the heat doesn’t want to go anywhere for the beginning of the month. Check out the 7-Day forecast here. Tuesday through Saturday all appear like they will at least be close to the 90 degree mark, with the hottest day for the remainder of the week Tuesday. Oddly enough, Reagan National Airport hasn't recorded four days in a row with highs at or above 90 degrees this year. The 15th through 21st of July 2013 was the last time we've experienced a prolonged period of high heat, with 7 days in a row at or above 93 degrees.

Last September also started off on a hot note, but beyond the first few weeks there was a nice cool down with a long stretch of days in the 70s. The average high is 84 degrees to start the month, but falls to 74 degrees by the end of the month.

90 degree days as of September 1

Temperatures should get back near normal come Sunday as cooler air moves in after a cold front. For the year, D.C. is still below the normal number of 90 degree days, with 19 as of Monday, compared to the 28 we were at by September 1st in 2013, and compared to the 36 average D.C. typically records in a year. With the recent hot summers, however, this is nothing compared to the record 67 90-degree days in 2010 or even the 56 in 2012, so at least it has been nice!

Monday's rainbow over D.C. captured by Richard Barnhill

Check out this beautiful picture from Richard Barnhill. You can find him on social media here and here, and check out his other pictures on flickr here.

What about storm chances the rest of the week? After a stormy past two days in parts of the area, a cold front will move into the region late Tuesday bringing an additional chance for afternoon storms. A break in the action will be likely Wednesday and Thursday before chances return Friday in an isolated nature and more widespread action with a potent cold front on Saturday.

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Labor Day Weekend 2014 weather forecast

August 28, 2014 - 04:07 PM
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Labor Day Weekend. For as long as I can remember, it has never been an easy forecast and has rarely featured perfect weather. Last year was really hot, with Saturday through Monday seeing temperatures of 92, 93 and 92 respectively. 2012 recorded 1.64" of rain to start the holiday weekend, 2011 ended the weekend with 1.36" of rain, and 2010 was near perfect, with plenty of sunshine, temperatures in the 80s and low humidity with dew points in the 40s and 50s.

That leads us to this weekend. The forecast has been favoring higher levels of heat and humidity to return to the region this weekend and hanging around for the start of September.

A warm front will be knocking on D.C.'s doorstep Saturday and high pressure will be centered in the northern Atlantic. This will lead to the aforementioned increase in humidity levels, meaning more clouds and dew points back in the mid to upper 60s. At this point, Saturday looks to be the coolest part of the weekend with highs in the mid 80s under partly sunny skies. It may even be mostly cloudy to start the day, but sunshine should filter overhead by midday. Even with the frontal boundary, Saturday should feature the lowest threat for rain, with the highest possibility in the mountains.

Temperatures should be the highest on Sunday (Image Courtesy WeatherBell.com)

By Sunday, the warm front will move north bringing in warmer air overhead. OK, let's call it hot air, as high temperatures are forecast to be in the lower 90s by the afternoon hours (See image above). Combine that with high dew points and energy sliding in from the west and afternoon thunderstorms appear to be a solid bet. Some storms may also be heavy rainmakers, as there will be abundant moisture in the atmosphere.

Below is a look at the forecast precipitable water values for Sunday, which when are this high in the 2 inch range, may mean the potential for some very heavy downpours. Be sure to keep an eye on Doppler Radar this weekend, and if you're out at the pool, find us on your phone!

Precipitable water values forecast for Sunday per the ECMWF Model (Image Courtesy: WeatherBell.com)

Monday will have similarities to Sunday, as the heat and high humidity won't be going anywhere fast. Troughing east of the mountains will set up by the afternoon again allowing for storm chances later in the day. Highs Labor Day aren't forecast to be quite as hot, topping out in the upper 80s to near 90 degrees.

Labor Day Weekend forecast updated Thursday Evening

 

Delmarva Beach Forecast

Rehoboth Beach, DE HD Camera  |  Ocean City, MD HD Camera 

Rehoboth Beach HD Camera Thursday Afternoon

How will the beaches fare this weekend? With the slight easterly component to the wind on Saturday, it may be on the cooler side to start, with highs around 80 degrees under partly sunny skies Saturday.

Sunday and Monday do look pretty nice at the beach. Temperatures should be in the low to mid 80s each day under partly cloudy skies. There is a slight chance for a few showers and storms late in the day, but right now the possibility is only around 20-30%.

Beach Forecast as of Friday morning

The rip current risk should subside by Friday and ocean conditions should calm down through the weekend. Regardless, you may want to double-check with the lifeguard before entering the water if you're not a strong swimmer.

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Hot End to Summer, What's Ahead?

August 28, 2014 - 07:47 AM
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August has been a crazy cool month, but we get one last hurrah from summer as the month ends.  So far there have only been two days when the mercury has reached 90 degrees or better in D.C. and none at Dulles.  Reagan National is running about a degree below average while Dulles had the 3rd coolest first half of August on record, and the month is ending about 4 degrees below average as of today.  However, the tables are turning and we will be close to 90 starting Saturday and continuing at least into the middle of next week.  Check out the latest 6-10 forecast showing well above average (85) temps.

 



6 to 10 day Outlook NOAA

 Typically as we enter September the temps wane.  Days get shorter and shorter with a loss of more than an hour of daylight by month's end.  Less heating of the earth means the average temperature drops from 84 at the start  of September to ten degrees cooler when it ends. 



September Climatology

 Two other notables for the first meteorological month of fall...  hurricanes and allergens.  First we'll talk hurricanes as Cristobal continues to churn in the Atlantic today.  Click here for the latest advisory from the National Hurricane Center. A high risk of rip currents continues on the Mid-Atlantic coast. Check out Lauryn's blog on that.  September is the peak of hurricane season. More major hurricanes are recorded this month than any other.  Conditions so far haven't been that favorable for tropical development with wind shear and coolish temperatures.  However, there is still time for that to change. There are a few areas of possible development. One in the Gulf of Mexico and the other in the Caribbean. 



Areas of Possible Tropical Development- NHC

 Here in the Mid-Atlantic we should always be prepared for a hurricane this time of the year. 

     September is also a bummer of a month for allergy sufferers.  While pollen has been moderate, the peak of ragweed season is here.  The first week of September usual has the highest pollen count for ragweed in the D.C. area.

 

 

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Rip Currents: A Deadly Ocean Phenomenon

August 27, 2014 - 12:45 PM
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We definitely have been lucky in the tropical storm department for the most of this year along the eastern seaboard (with the exception of Hurricane Arthur in early July which did lead to some flooding). Hurricane Cristobal, which is churning just about 300 miles of Cape Hatteras, North Carolina, Hurricane Cristobal will continue to move north-northeast avoiding the east coast of the United States.

ZZZZZ

 

However, areas along the eastern seaboard will still indirectly get in on some of the action of Hurricane Cristobal and beachgoers are already starting to feel the effects.

All along the eastern seaboard, from Florida up through New York and Boston, a moderate to high risk for rip currents are being forecast as well as high surf advisories with large crash waves. Rip currents could occur so frequently that a lot of beachgoers for this last week in August are forbidden to enter the water considering the threat for rip currents is so high that it would be life-threatening to anyone entering the surf. These forecast include local Maryland, Delaware and Virginia beaches.

Heading into Labor Day weekend and with the unfortunate and untimely death of an 18 year old whom drowned Tuesday night in Ocean City, Maryland from getting caught in a rip current, I think it would be great to revisit rip current safety: how to recognize a rip current and how to properly save yourself. These currents can occur along any beach that features breaking waves (including the Great Lakes) and they are unfortunately subject to formation at any time during the day and more likely right before or just after low tide. The swells generated by Hurricane Cristobal and brisk onshore flow are creating the environment for a higher risk of rip currents.

According to the U.S. Lifesaving Association statistics, rip currents cause more than 100 drowning fatalities each year and 80% of all rescues on surf beaches nationwide are rip current related. Now, rip current speeds can vary and although rip currents at any speed are particularly dangerous for weak or non-swimmers, some have even been measured as fast as 8 feet per second-which is faster than an Olympic swimmer can swim! Generally though rip current speeds are typically 1 - 2 feet per second.

 So how do these things form and why? Well first what is a rip current? It can be summed up as a fast-moving narrow section of water that travels in the offshore direction. In some cases, the width of the rip current can extend to hundreds of yards.

ZZZZZ
ZZZZZ
ZZZZZ
(Photos courtesy of National Weather Service)

Now how do these rip currents form? As waves near the shore and heads from deep water to shallow water, they break. As the waves break, they generate currents that flow in both offshore/seaward (away from the coast) and alongshore directions. Currents that flow away from the coast are called rip currents.

ZZZZZ
ZZZZZ
(Photos courtesy of National Weather Service)

Although all beaches are susceptible to rip currents, the shape of the shoreline, the location of jetties, sandbars, groins and piers and the nearshore bottom design or bathymetry can all influence rip current development. Therefore, there are some beaches that are more prone to rip currents due to their topography.

So how to you identify rip currents?

Look for either one or more of these clues:

1. a channel of churning, choppy water

2. an area having a notable difference in water color

3. a line of foam, seaweed or debris moving steadily seaward

4. a break in the incoming wave pattern

Some rip currents can be weak and slow and be little to no threat for experienced swimmers, however, that can all change with a size or intensity of the next incoming wave. A strong wave can causes pulses in the strength of a rip current-so always be aware although most of the time, rip currents are not easily identifiable. *Safety tip - Polarized sunglasses make it easier to see rip currents*

Now on to the next: How do you survive rip currents?

First thing first: if you find yourself caught in a rip current, REMAIN CALM. A rip current is a horizontal current. They do not pull people under water but instead, pull them away from the shore. Most of the deaths that occur from rip currents happen when people are pulled offshore and are unable to keep themselves afloat because they can't swim to shore.

So here are some tips: Once you calm yourself, you can think more clearly so remaining calm is number one!

Secondly, DON'T FIGHT THE CURRENT. Swim out of the current parallel to the beach/shoreline. When you feel that you are out of the current, swim back towards the shore. If you are unable to swim out of the rip current, float or calmly tread water until you feel that you are not being pulled anymore. Don't exert any extra energy. Now, if these tips do not work, draw attention to yourself: face the shore, wave your arms and yell for help.

 

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(Photo courtesy of National Weather Service)

 Contact a lifeguard or 911 if needed! Many people drown while trying to save someone else from a rip current. The best thing you can do it throw the victim something that floats and yell instructions on how to escape.

ZZZZZSo enjoy the beach for the rest of this summer but remember that rip currents can happen along any beach with breaking waves! Keep you and your family safe and take the warning seriously.

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Fog Season Arriving in the Washington Area

August 24, 2014 - 06:22 PM
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Fog is a subtle weather condition that can quickly become dangerous for commuters, walkers, bikers and runners without advanced warning. It doesn’t come with a bang like a thunderstorm or can be seen slowly piling up like snow, but rather slowly and quietly develops, usually at night, and can cause serious and abrupt visibility problems the following morning.

Fog is typically found in the cooler season because of the longer nights, which allow the temperature to drop to the dew point and condense suspended moisture in the air. Also, stronger storm systems often occur later in the fall (November particularly) which can produce foggy scenarios.

A recent study from the National Weather Service in Blacksburg, Va., showed that nearly 65% of fog events for the Blue Ridge foothills and Piedmont occurred November through February. Only 13% widespread dense fog events happen in the spring and summer.

Fog graph

In most of the fog events studied, a key feature was the position of a strong surface high pressure. High pressure produces sinking air, which results in clear skies and light wind (the perfect recipe for fog). When high pressure is anchored along or off the East Coast, the Mid-Atlantic tends to have foggy nights.

The upcoming pattern this week favors a similar set up where high pressure will be focused across the Mid-Atlantic and southern New England.

Surface map

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Tropical Storm Cristobal Forms

August 24, 2014 - 09:00 AM
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An Air Force Reserve Hurricane Hunter aircraft investigating a disturbance near the southeastern Bahamas determined that the system has become organized enough with a well-defined circulation to be classified Saturday night and as of Sunday Cristobal becomes our third tropical storm of the season.

Enhanced Satellite Loop

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The Threat of Rain Continues This Week

August 19, 2014 - 02:42 PM
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If you like cloudy, muggy and gloomy weather then this week is your week. Fortunately, temperatures will be held at bay, only reaching into the lower to mid-80s for daytime highs Tuesday, Wednesday and Thursday but the humidity will continue to stream into viewing area as the region is wedged between an area of high pressure to the north and an area of high pressure to the southwest (take a peek at the graphic below).

ZZZZZ

Courtesy of The National Weather Service Baltimore-Washington

A frontal boundary will also continue to be draped across our region and will continue to meander in the vicinity of central Virginia and the D.C. metro area at least through Thursday. That frontal boundary will be the main forcing mechanism for any showers or small thunderstorms that pop up around the region Tuesday afternoon. This means that generally any rain that pops up will be around the stationary front getting caught up in our easterly flow and will preside mainly just south of the Washington D.C. metro area on Tuesday afternoon and evening. Unfortunately, since there is so much moisture and the fact that there is no element that is moving these cells along quickly, are few could contain isolated downpours. Good news is that I don’t anticipate any widespread severe weather for Tuesday evening and into Tuesday night.

ZZZZZ

The frontal boundary is just to the south of Washington D.C. on Tuesday afternoon, draped across Fredericksburg through Southern Maryland and back to the west around the Eastern West Virginia Panhandle.

If you are headed out to Nats Park tonight, just know it will be a little on the steamy side but I do believe that we will remain dry. Plenty of clouds will stick around through the duration of the game against the Arizona Diamondbacks as temperatures drop through the 70s. There could even be some areas of fog that form while you make your way home from the stadium.

ZZZZZ

Overnight temperatures on Tuesday will only fall to right around 70 degrees in most locations and warm back up into the mid-80s once again tomorrow. There could be a few peeks of sunshine once again Wednesday but an upper level low, diving out of the northwest, will be headed this way.

A piece of energy out in front of that low will move into the region Wednesday afternoon through Wednesday evening. This means we have a good chance to see some showers and thunderstorms around the region. Most of the activity will die off in the evening hours as we lose our heating from the day but there is a about a 20% chance that a few showers or storms could linger into the late evening hours leading into Thursday.

By Thursday morning, that upper level low (reference the first graphic from the National Weather Service for more information on the upper level low) will be nearing our area, crossing through during Thursday afternoon and Thursday evening bringing us yet another chance of some showers and thunderstorms. This time, there is about at 50% chance of scattered showers and thunderstorms around the region on Thursday.


The best chance for a good soaking rain comes on Thursday but all in all expect less than a 1.00” in total rain accumulation from Tuesday throughThursday night. This will be good because if you have found yourself sniffling a little through the weekend and into the first part of this week, around the D.C. region mold, grasses and weed pollen is all running a little on the elevated side. So it will be good to get some rain to alleviate some of those allergies.

 

ZZZZZQPF or Quantitative Precipitation Forecast shows 1.00” of less of rain accumulation around the WJLA viewing area from Tuesday through early Friday morning

Due to the rain that we received through the first half of August, we are well over our normal averages for rain during the summer (June – August 19th) at Reagan National Airport as well as Baltimore-Washington Airport (in fact, the rain that fell on Tuesday, August 12th put BWI +4.38” over their normal rainfall amount for the summer). Dulles International Airport could still use some rain however, as they are behind a little over 1.50” for rain accumulation for the summer months.

And while we are at it, to be completely honest, I am still not sold on keeping Friday through the weekend dry. I have continued to have it dry in my forecast for the last two days but I believe it is going to be a wait and see game to if this pattern sticks through Friday and into the weekend or to see if high pressure can edge out bringing some more pleasant conditions. Either way, we will keep an eye on it for you and let you know as the picture becomes clearer.

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3rd Coolest August on Record at Dulles and Baltimore

August 16, 2014 - 09:15 PM
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While we have experienced some seriously beautiful weather so far this August we have also had several very chilly mornings in the Mid-Atlantic.  When you average the high and low temperatures together, we rank in the top three coolest months of August up to this point at Dulles and Baltimore.  Here is a graphic from the National Weather Service that shows our average temperature so far from August 1st through the 15th compared to the averages and records for the month.

 

 

 


August Statistics- National Weather Service

 

 

 

 

 Not once did the thermometer at Dulles or BWI reach 90 degrees in August of 2014.  87 was the hottest day of the month at Dulles, VA on the 5th.  If we take a look at Reagan National, while it was also cooler than average, it definitely tells a different story.

 

 

 


August Statistics at Reagan National Airport

 

 

 

  The average temperature here is less than two degrees below the normal of 77.1.  It did hit 90 degrees, but only once on the 5th.  And it doesn't even make the top ten coolest Augusts on record.  It really goes to show you how different weather can be just a few miles apart in our region.  Now that the month is half over, what can we expect as we end it?  Will there be a big warm up? 

 



6 to 10 day Outlook

Well, at least a bit of one...   The medium range forecast has temperatures near the seasonal average with above average temps nearby .  We could hit 90 in there for a day or two if we're lucky (yeah, I wouldn't mind one more).  So far, D.C. has had 16 days at 90 degrees or above.  On average, we get between 25 and 30 of them in a year.  The summers with the fewest 90 degree days were in 1905 and 1886 when there were only 7 days. (Thanks to Alex Liggitt and a previous blog for those last two stats). 

 

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