From the ABC 7 Weather team

Severe Storms Possible Sunday and Monday

July 25, 2014 - 03:07 PM
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Say goodbye to the beautiful weather of Friday and hello again to summer in Washington, D.C. for the weekend. That means a return of heat and humidity as well as a return of summertime thunderstorms. Saturday will feature very warm temperatures, right around 90 degrees for a daytime high with increasing clouds and increasing humidity late in the day. Another thing that will increase on Saturday will be the chances of showers and thunderstorms. Albeit, it is only a slight chance of showers and thunderstorms through the PM and overnight hours on Saturday, but still a chance.


An upper level piece of energy will approach the region on Saturday night. Mainly our western areas will be the breeding ground for any action, but by Sunday, we all have equal chances to see showers and thunderstorms across the area as that disturbance passes through the D.C. area.

ZZZZZ

 

Also what we are watching after Sunday’s disturbance is a very strong cold front will be dropping out of the upper Midwest and down into the region for Monday. Therefore, we have a chance of showers and thunderstorms Saturday night – Monday, some of which could be strong to severe.
Above graphic, at the top, shows the slight risk area for severe weather Saturday through Monday. The risk moves from the Ohio Valley Saturday to our area on Sunday and Monday. On the bottom of the graphic, the surface features show an area of high pressure overhead bringing us very pleasant on conditions on Friday. Then through 8 p.m. Saturday, the area of high pressure scoots off the coast giving us a southerly flow bringing humid air from the south and transporting it right here into the D.C. area as a warm front approaches the region. By Sunday and Monday morning, the strong cold front is still to the north and west of the area.


So now that we know what is going on, what can we except through the weekend? Well considering that warm front is just to the south on Saturday night, lift from warm advection around the warm front and the piece of energy approaching us from westerly flow aloft will give us that about a 20% chance of storms on Saturday afternoon and evening continuing through the overnight hours. There will be a good chance of severe weather across our area through the day on Sunday as that disturbance moves through the region. One thing that still remains a question is temperatures on Sunday. Right now I have temperatures fairly warm, nearing 90 degrees. But, if we get some thunderstorms in the morning hours, that could down our temperatures for the afternoon and lessen the instability in the atmosphere. Either way, it will still be very muggy outside through the day on Sunday with mainly clouds hanging around. Some of our models do suggest that we get some thunderstorms during the first part of the day on Sunday.

 

ZZZZZ

 

Caption: Showers and thunderstorms around the region weaken slightly as they travel to our area from the north and west. This is around 11a.m. on Sunday.

We do know that any of these storms could produce damaging winds, possible hail and heavy rain. There will certainly be substantial moisture around the region given the nice southerly flow, therefore localized flash flooding is definitely a concern. Take a look at our precipitable water values:

 

ZZZZZ

 

You may have heard this term or “PWATS” quite a bit this summer. Really what preciptable water values are are the amount of water within a vertical column above the surface if it were all precipitated out. These values are over 2.00” in some spots and when we see that, we know there is enough moisture available to create flooding conditions.


By Monday, the chance of showers and storms remains through the day as the cold front finally travels through the region. Again, some of there could be strong to severe but by Tuesday, we are in for another treat.

ZZZZZ

A nice refreshing airmass moves into the region bringing low humidity and refreshing temperatures. Daytime highs on Tuesday are in the upper 70s to lower 80s! We just got to make it through some summertime storms to get the reward by mid-next week!

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Cherrystone tornado rated EF-1

July 25, 2014 - 11:46 AM
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The National Weather Service office in Wakefield, VA surveyed the damage from yesterday morning's storm in Northhampton County in southeastern Virginia and determined the damage was due to a tornado, straight line wind, and a large swath of hail.

Path of the tornado, straight line wind and large hail

Above is a look at the path of the tornado, wind and large hail. The tornado originated in the Chesapeake Bay as the storm rapidly intensified. The EF-1 tornado had estimated maximum wind speeds of 80 to 100 mph and was on the ground for 8 miles over a span of 15 minutes. It's maximum width was 150 yards. The tornado wasn't the only feature that caused damage in this storm.

A downburst resulting in straight line winds was observed in the yellow wind damage swath. Wind speeds were estimated between 65 and 75 mph and downed numerous trees and even contributed to overturning several camping trailers in the Cherrystone Campground.

The hail core fell mainly within the blue lines (first image above) in the size of golfballs to a few reports of baseball size. This caused considerable tree and leaf debris, crop damage and siding damage on homes in the path.

The storm caused 36 injuries and 2 fatalities.

See the rest of the preliminary storm survey here.

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Average hottest days in D.C. in the rearview, daylight diminishes

July 23, 2014 - 12:18 PM
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With temperatures forecast to be in the low to mid 90s, one wouldn't think the average hottest days are behind us, but the average high drops to 88 today. Don't worry, cold air isn't exactly going to march right into the D.C. area, as the average high temperature remains in the mid to upper 80s through the month of August. August also averages nearly 10 90-degree days, something we haven't seen too much of this year.

90 degree days in D.C.

In fact, D.C. is actually below average for 90-degree days so far this summer, with only 15 this year. Compare that to last year, which recorded 21 by the same time. Typically there are around 36 90-degree days per year in the D.C. area, so it appears this summer may go down as below average in that category. Ninety-degree days or not, this summer has still been above average, with temperature departures of +2°F in June and +0.5°F so far in July. We'll see how August fares.

Looking ahead, the heat will briefly subside Thursday and Friday but will return for the weekend. Highs should top out in the 90s both Saturday and Sunday, prior to a big-time cool down next Tuesday through the end of the month. Highs may only reach the 80-degree mark next Tuesday!

Duration of daylight for D.C.

Daylight continues to diminish since the summer Solstice, with 28 minutes gone in just a month's time. An additional 14 minutes of daylight will be lost by the end of the month, and over an hour more will be lost by the end of August, so enjoy it while it's here.

While this may be a depressing blog post for some, after summer, there's always cooler and crisp days, fall colors, the Nats playing in October, the Skins taking the field, and plenty of other great things to look forward to. Here's to a fantastic last 39 days of meteorological summer to go!

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45th Anniversary of Landing on the Moon

July 20, 2014 - 05:00 AM
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"One small step for man, one giant leap for mankind".  These are the words Neil Armstrong said 45 years ago today after he stepped onto the surface of the moon.

Astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins were all aboard the infamous Apollo 11 flight to the moon.

NASA

The three launched into space aboard Apollo 11 on July 16, 1969 via the Saturn V rocket at the Kennedy Space Center in Florida.  Armstrong and Aldrin then climbed into the lunar module Eagle (below) that would descend onto the moon, while Collins orbited in command module Columbia.

NASA

At 4:18pm EDT, Armstrong connected with mission control in Houston saying "Houston, Tranquility base here.  The Eagle has landed". 

At 10:56 pm EST, Armstrong set foot onto the surface of the moon.  You can see in the image below the American flag the astronauts planted on the lunar surface.

NASA

Buzz Aldrin then joined Armstrong on the moon and the two spent time deploying instruments that would be used for experiments, gathering samples of lunar soil, and taking pictures. 

Here's a great "Moonwalk Montage" that takes us back to that day:

 

The three astronauts accomplished something the Russians had not.  NASA states they did not want to focus on the "victory" of the mission, but rather emphasized the "peaceful lunar landing by the United States. 

The patch designed for the mission was created by Michael Collins.  On the patch, the American Bald Eagle is depicted landing on the lunar surface, delivering an olive branch of peace.   The words "Apollo 11" were chosen for the top of the patch above a distance crescent shaped Earth.

NASA

The United State's determination in exploration through the Space program has taken us to the point where we now have a rover on Mars.  The mission 45 years ago today reemphasizes the spirit of our country and the desire to explore and discover outer space.

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Severe Storms Likely Monday and Tuesday

July 13, 2014 - 06:39 PM
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We've reached the climatological hottest time of the year in D.C. with our average high now 89°.  Some big changes on the horizon, as a strong cold front approaches the area.  This cold front will bring a welcome drop in the heat and humidity by Wednesday, but it will come with the price of severe weather for Monday and Tuesday.

Ahead of the front, our airmass remains very hot and humid.  Forecast high temperatures Monday are in the low to mid 90s.  Factor in the humidity and it will feel closer to the 100 degree mark.

The cold front will slide farther east Monday increasing the atmospheric dynamics for severe weather.  Take a look at the surface features, as of Sunday night.

The viewing area will remain under the very warm and moisture laden air until the cold front passes late Tuesday night.  That will help fuel the fire for the strong and severe storms.  The Storm Prediction Center has the entire vewing area (shaded in yellow in the image below) under a 'Slight' risk for severe storms Monday.   This means damaging winds (60+mph), large hail, and isolated tornadoes will be possible with any storms that develop.

Storm Prediction Center

A big dip in the jet stream will allow temperatures and humidity to drop off significantly by Wednesday and the rest of the week.  The clash of airmasses; however, is what is causing this elevated risk for severe weather.  Check out an upper level map (500mb level) that clearly shows the large trough digging into the area.  The brighter colors indicate higher wind speeds, which leads to increased wind shear.  Wind shear can cause damaging wind gusts and tornadoes.

WeatherBell - European Model 500mb heights and wind speed/direction

As mentioned, behind the front much cooler and drier air.  Take a look at the difference in forecast dewpoint temperatures on Monday and Wednesday.  Dewpoints will go from the mid 70s Monday afternoon to the low 50s Wednesday.  You will certainly feel the difference by midweek.

WeatherBell ECMWF Dewpoint Temperature Monday
WeatherBell ECMWF Dewpoint Temperature Wednesday

Remember to stay updated with the StormWatch7 weather team for the latest weather updates.  We also encourage you to download the free StormWatch7 weather app.  You'll have access to Live Super Doppler within the app, so you can track storms on the go.

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Cooler Air, but Not Cold Air Infiltrating the D.C. Area Next Week

July 12, 2014 - 05:10 PM
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Once we get through the possibility of severe storms on Monday and Tuesday, cooler air will move right into our region for the end of next week.


Classification. Yes, we are a society that likes to name things: Snowmaggedon, Commutergedon, SnowGuinness, etc. Where a squall line is a “derecho” and where a spill of cold air from the north is coined the “polar vortex.” I get it. I really do. Classification of tornadoes or hurricanes is absolutely necessary, however, to call every snowstorm a “blizzard” just makes me shake my head-but then move on with my life.


Before 2012, we had NEVER heard of the term “derecho” and now it seems every storm that comes through during the summer is classified as that. Before last winter, we NEVER EVER heard the term “polar vortex” used before and now, several months later, we gravitate right to it.


It is all in the eye of the beholder and left up to interpretation amongst professionals in the meteorology field. Although I didn’t want to touch this subject with a ten foot pole, I feel that we are forced to say something. The storm on Tuesday night left so many people wondering whether a “derecho” in fact hit the area that we had to reach out to the Storm Prediction Center to include their thoughts. So now onto the “polar vortex” or let’s just say the “unusual pattern setting up for Mid-July.”


All in all, we do know that next week unseasonably cold air will migrate out of the north and into the United States, spreading out into the Mid Atlantic. There is so much misuse of several weather terms throughout the year that I thought we should revisit the term “polar vortex”.


Our friends at the National Weather Service in New York made this graphic after the hysteria in social media yesterday about “the return of the polar vortex.” They reminded everybody on their Facebook page that “the most basic definition for “polar vortex” is that it is a piece of energy that comes from the polar region. It is generated by the large difference in temperature between the tropics and the poles. The temperature gradient is strongest during the winter; therefore it is more likely to affect mid-latitudes (our area) in the winter. However, it can affect us in the summer, but it is not nearly as strong as it is in the winter.”

NWS

There are differing opinions in the meteorology field on whether this is a “true polar vortex’ and that is why you will see so many different articles ALL OVER the internet on whether this is or it is not. This is what the Weather Prediction Center put out yesterday:\


“A DEEP UPPER LOW... NOT THE POLAR VORTEX AS ITS ORIGINS ARE FROM THE NE PACIFIC... WILL SWING THROUGH THE GREAT LAKES EARLY NEXT WEEK WITH AN IMPRESSIVE COLD SHOT OF AIR INTO THE CENTRAL AND THEN SOUTHERN PLAINS AND THE MIDWEST.”


Great. So in the grand scheme of things I ask myself “does it really matter to the general public what we coin this?” The answer I give myself is “no”.
So here is what we know. We have some unseasonably cold air coming down from the north and spilling into the region. The Midwest will get the brunt of the cold weather where temperatures could be as much as 20-25 degrees below normal! That is very impressive for summertime climate. Our normal temperature in the D.C. area for this time of year is a warm 89 degrees. The Climate Prediction Center has given us about a 40%-50 of seeing below normal temperatures next week.

Climate Prediction Center

Now, I got to tell you, if you are expecting temperatures in the 50s/60s then you have to travel to the north and west of here. Temperatures next week (starting Wednesday) are going to fall below normal but we are still talking 70s/80s. Here is a look at our 7-day forecast:

However, before we even get to that cooler air moving in, as you notice on the 7-day we are heating up! Temperatures on Sunday, Monday and Tuesday will have no problem reaching into the 90s. With the added July humidity, we are talking about heat indicies approaching 100 degrees all with the added threat of severe weather each day. The Storm Prediction Center has ALREADY outlined us in an area for a shot at severe weather on Monday into Tuesday:

Storm Prediction Center

So all in all, are we cooling down slightly for the end of next week? Yes. Are we going to have to deal with heat and humidity and severe storms at the beginning of next week? Yes. It is going to be a roller coaster week and we will certainly welcome the cooler air by the end of next week, not matter what we want to call it.

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Full "Supermoon" Tonight

July 11, 2014 - 09:42 AM
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It's that time of the lunar calendar where we approach full moon status.  The moon will be full tomorrow morning at 7:25am.  But even tonight, expect a 14% bigger and 30% brighter full moon than full moons of 2013.  The reason?

The moon is in perigee.  The terms perigee and apogee refer to the distance of the moon from the earth.  During perigee the moon is closest to Earth.  The opposite is true when the moon is at apogee. 

NASA

Tonight's full moon will be the first of three supermoons this year.  The next will occur on August 10th and the final on September 9th.  The full moon tonight will be less than 224,851 miles away from Earth.  To put that in perspective, at apogee the moon is roughly 252,000 miles away from Earth.  Here's a photograph of the two full moons overlayed on one another. 

NASA

The July full moon is referred to as the "Buck" or "Thunder" moon.  The buck moon came from deer's antlers pushing out of their forehead.  The moon is also referred to as the thunder moon because July is the most common month for thunderstorms.

NASA

Weather conditions for supermoon-viewing will fairly good. Aside from a few scattered clouds, the sky should feature the bright moon rising at 6:46pm tonight and setting at 5:02am tomorrow morning. If you take some moon pictures, we'd love to see and share them! Happy moon viewing!

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Flash Flood Watch for the D.C. area until Midnight

July 10, 2014 - 03:48 PM
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DOPPLER RADAR  |  WATCHES/WARNINGS  |  STORMWATCH 7 FACEBOOK

A Flash Flood Watch is in effect through Midnight tonight for the majority of the D.C. area. Showers and storms along a frontal boundary are moving extremely slow, allowing for a prolonged period of heavy rainfall. Baltimore experienced its own storm earlier today which dropped a radar estimated 2.5 inches of rain. Additional storms may do the same for parts of the D.C. area through tonight.

Flash Flood Watch in effect until Midnight

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Rocket Launch from Wallops on Saturday

July 10, 2014 - 07:04 AM
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First it was engine trouble and then thunderstorms delaying the launch of an unmanned commercial rocket that will resupply the International Space Station.  As of today, all signs point to a "go" for the Cygnus Rocket launch at 1:14p.m. on Saturday at Wallops Flight Facility in Virginia. The rocket was rolled out onto the pad this morning at Wallops as shown here in a tweet by NASA.


Antares Rocket on the Launch Pad at Wallops Flight Facility

 The rocket will be carrying 3,300 pounds of supplies for the ISS, including food, science experiments to expand the research capability of the space station's Expedition 40 crew members, and tools.  Many student experiments will be on board as well.  This is the second of eight scheduled rocket launches for Orbital Sciences, a private company based in Virginia that has a contract with NASA for the resupply  missions.


Orbital Sciences

 Although the launch will take place in the daylight hours, the burn off from the rocket may still be bright enough to see, even here in Washington, D.C.  Weather looks cooperative with partly cloudy skies forecast. You need to look at about 5 degrees above the  horizon in the southeastern sky about a minute or two after the launch.  Here is a map where it would be visible.

 


visibility of launch expected from Orbital Sciences

 You can also watch it live on NASA TV starting at 12:30p.m. ET.  If the launch happens on time, it will reach the International Space Station on Tuesday, July 15th. 

 

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Storms possible through this evening in the D.C. area

July 9, 2014 - 03:35 PM
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LIVE DOPPLER RADAR  |  HD CAMERAS  |  WATCHES/WARNINGS

A Severe Thunderstorm Watch has been posted for much of the D.C. area until 10pm. This comes out after the Storm Prediction Center stated a watch would be unlikely for the D.C. area about an hour ago. After a few storms exhibited damaging winds, it appears they've changed their minds and decided to post one for the region through this evening and early tonight!

Severe T-Storm Watch until 10pm

Showers and thunderstorms will continue to be possible through the afternoon and evening, so please listen for the latest on where they are located and be sure to check Live Doppler Radar before going outside.

Storms will have the potential for heavy rainfall, frequent lightning and gusty winds. We will cover them live on ABC 7 News at 5pm and 6pm.

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Severe Thunderstorm Watch in the D.C. area Tuesday

July 8, 2014 - 07:06 PM
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As expected, a Severe Thunderstorm Watch has now been expanded to include the entire ABC 7 News viewing area until 11:00 p.m. Storms will likely bring periods of heavy rain, gusty winds and small hail. Wind gusts may exceed 70 miles per hour in some storms.The watch for western Maryland will expire at 8:00 pm. For the counties included, click here. Stay with ABC 7 News for additional update.

LIVE DOPPLER RADAR HERE

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July Weather in D.C.: Hot, Humid & Stormy

July 6, 2014 - 06:09 PM
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The mercury will soar into the 90s while heat indices climb close to 100 degrees early next week. In the meantime, a cold front will likely ram into this heat and humidity, triggering midweek thunderstorms once again.

Downpours and gusty winds are likely with the first round that breaks the heat spell either late Tuesday evening or Wednesday afternoon. This pattern is all too common across the Washington metro area.

Analyzing past weather trends since 1980, July tops the list for the most combined hail, wind and tornado events in the region (see table below).

July Climatology

The biggest threat from any single thunderstorm in July is wind gusts. In order to qualify as a severe thunderstorm, gusts must at least reach 58 mph. July also ranks #1 for the most tornadoes area-wide. On average, there are 6 tornadoes in the region (the western Maryland panhandle into the Shenandoah Valley, northern Virginia, the District and all the way to the Chesapeake Bay) during the month of July.

Notice the breakdown of severe weather reports per hour on any given day. Hail, gusty winds and tornadoes are most common at 6 p.m. (22 UTC = 6 p.m. between daylight saving time (in early March) and standard time (in early November). This makes sense given the atmosphere is generally most unstable late on a summer's day after the sun has been warming the ground all day.

Hourly Severe Climatology

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Arthur Update and Fireworks Forecast

July 4, 2014 - 09:05 AM
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Hurricane Arthur has put a damper on numerous firework's displays with many locations having to postpone or cancel.  Fortunately for us, the fireworks should be able to get off without a hitch in the Nation's Capital.  Here's a list of cities where fireworks have been rescheduled.

Hurricane Arthur made landfall near Beaufort, N.C. around 11:15 p.m. Thursday night.  Arthur was downgraded to a category 1 hurricane with winds at 90 mph as of the 9 a.m. update from the National Hurricane Center.  The storm has moved off the coast of the Outer Banks, NC and is quickly moving northeast.
(National Hurricane Center)
As a cold front slides through our area and Arthur moves farther out to sea, skies will clear from west to east, as drier air filters in.  It'll also be quite breezy, with winds gusting to around 30 mph through the day.
Winds will subside by the time the fireworks are set to go off downtown at 9:10pm.  And we couldn't ask for a more pleasant fireworks forecast.  It will be very comfortable, with low humidity and still just a bit breezy.  Click here for a full list of Fourth of July parades, events, and fireworks' displays.
The rest of the holiday weekend looks fantastic!  The humidity will remain low with plenty of sunshine and seasonable temperatures.

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Severe Thunderstorm Watch until 9 p.m. Thursday

July 3, 2014 - 01:24 PM
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LIVE DOPPLER RADAR

A Severe Thunderstorm Watch is in effect for the majority of the D.C. area until 9 p.m. tonight. Storms will continue to develop mainly southwest of D.C. and move into the region closer to the evening rush around 5 p.m. to 6 p.m. Very heavy rainfall will be possible in storms, which is why the National Weather Service also put the entire area under a Flash Flood Watch. Be sure not to cross any flooded roadways.

(Severe Thunderstorm Watch until 9 p.m.)

Storms will linger through late this evening but should diminish overnight. A few showers will be possible through the morning hours as the front continues to move through the region and Hurricane Arthur approaches from the south.

Find the latest on Hurricane Arthur here.

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Hurricane Arthur: First Hurricane of the Atlantic Season

July 3, 2014 - 06:14 AM
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As of the 8am update from the National Hurricane Center,  Arthur is now a Category 1 hurricane with max winds of 80 mph and moving north/northeast at 8 mph.  Check out the storm via satellite and radar.   

NOAA
Intellicast Radar

The storm is currently bringing rain to eastern South Carolina and is expected to pass over eastern NC later tonight.   Mandatory evacuations are already in place for Hatteras Island, NC.   Hurricane warnings are in effect for these areas, as heavy rain, gusty winds, coastal flooding, and dangerous surf are expected. 

NWS Morehead City, NC

Arthur is projected to brush the Carolina coast tonight and be off the mid-Atlantic coast by midday tomorrow.  Check out the latest track map from the National Hurricane Center.

National Hurricane Center.

Our local impact from Arthur will occur today.  As a cold front approaches from the west, and tropical moisture from Arthur feeds into our area, severe storms and flash flooding will be possible this afternoon and evening.  The Storm Prediction Center has our area in an elevated risk for severe storms with damaging winds.  The National Weather Service has also issued a flash flood watch for later today, as well.

Storm Prediction Center
NWS Sterling, VA

The cold front will slide east tomorrow morning and help push Arthur farther out to sea.  Drier air will slide in from west to east through the day tomorrow.  It should be rather delightful for the fireworks displays tomorrow evening with low humidity, comfortable temperatures, and a nice breeze.

The rest of the holiday weekend forecast looks great.   Have fun and be safe!

 

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Tropical Storm Arthur: Forecast Track

July 2, 2014 - 05:30 PM
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Tropical Storm Arthur as of 5 p.m. Wednesday has maximum sustained winds of 70 mph and is moving slowly to the north around 7 mph. It is currently centered around 220 miles south-southeast of Charleston, South Carolina. .

Arthur is encountering some upper-level dry air north and west of the center but conditions are still favorable for intensification in the next 24 hours or so. The forecast continues to show Arthur as a Category 1 hurricane with winds around 85 mph by the time it approaches the Outer Banks of North Carolina.

The storm is expected to continue to the north today before a slight turn to the northeast into Thursday morning. As it approaches the Outer Banks and Mid Atlantic, the system will start to push farther northeast into the Atlantic as it encounters the frontal boundary which will move into our area today and tomorrow. This will be the feature that you can thank for hopefully making for a dry 4th of July fireworks display.

8am NHC forecast track update

For Friday, expect cloudy skies, breezy winds and possible showers in the morning hours in the D.C. area. The best chance for rain will be east of the city. Conditions should improve by the afternoon, with a little bit of clearing and diminishing breezes. Temperatures will be more comfortable in the mid 80s and humidity levels will fall with dewpoints back in the low 60s and upper 50s. Not like our typical 4th of July!

WPC QPF forecast for this morning through Saturday morning

If you are heading to the beaches, including the Delmarva, heavier rainfall is more likely along with high surf and gusty winds. Thursday and Friday will be the worst. Heavy rain, high surf and gusty winds will be likely, so get your movie tickets soon!

Saturday and Sunday will be sunny and warm, but dangerous rip currents will continue to be a likelihood as the remnants of the storm move farther northeast into the Atlantic. Keep this in mind if you are heading there and be sure to check with the lifeguards before entering the water if you aren't a strong swimmer or familiar with rip currents.

Check back here for the latest updates.

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Severe thunderstorm watch until 8 p.m. Wednesday

July 2, 2014 - 01:11 PM
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High heat and humidity combined with an upper-level disturbance moving through the region will create the possibility for severe weather this afternoon. Strong to severe thunderstorms will be possible with the potential for damaging winds and large hail.

(Severe thunderstorm watch until 8 p.m.)

The watch continues until 8pm this evening. In addition, a Heat Advisory is still in effect for the majority of the D.C. area through 7pm this evening. Heat index values may approach 105°F this afternoon so please try to limit your time outdoors if possible.

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Tropical system may impact the D.C. area for the 4th of July

June 30, 2014 - 11:37 AM
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All interests in the Mid Atlantic and East Coast are turning to the Atlantic Ocean off the coast of Florida, as a weak area of low pressure continues to sit over the area. Conditions aren't expected to be conducive to tropical development with wind shear hampering development, but there are already reports of tropical storm forced winds in the system.

Visible satellite image of the disturbance

Above is a look at the system, which has very little thunderstorm activity at the moment. Much of the storm activity is situated south and east of the center of circulation, which is very poorly defined at the moment. An Air Force Reconnaissance Aircraft is on the way to investigate the system for the next few hours.

Model track guidance depicting the system to move north the rest of the week

Model guidance is depicting this system to drift southward a bit today before moving north along the east coast through the week. The timing brings the possibility of the system to the Mid Atlantic region by Friday morning and out of the area by Friday night.

Model intensity guidance depicting possibility of a Tropical Storm

Intensity forecasts depict the potential for a Tropical Storm by Wednesday or Thursday. This would make for a poor 12 to 24 hours if you are at the Outer Banks, Virginia Beach or north to the Delmarva and Jersey Shore.

While the track forecast doesn't directly impact D.C., the combination of a possible tropical storm along with the interaction of a frontal boundary and approaching region of high pressure from the northwest would result in clouds, the chance for rain as well as breezy winds.

QPF through Saturday morning

The heaviest rain should be limited to the coastlines. Sorry beach-goers. Gusty winds will also be possible along the coasts, though confidence is still rather low.

Your best bet as of now will be to monitor the latest forecasts through the week. We will be sure to keep you updated with the latest information

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Two Year Anniversary of the Derecho

June 29, 2014 - 05:00 AM
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It's a name and date we'll always remember.  June 29, 2012.  The derecho. 

Before that day, most of us had never even heard the term 'derecho'.  After that storm, it's a name we all remember. 

That Friday was one of the hottest days of the year.  In fact, one degree shy of the hottest temperature recorded at Reagan National.  The high reached 104 degrees (a record for the day).  With such high temperatures and humidity, the atmosphere was primed for severe weather.  Little did we know how widespread, and devastating, the severe weather would be.

The line of severe storms originated in Indiana, moved through Ohio and parts of West Virginia, before slamming our region between 9 p.m. and 11 p.m. that Friday night.  Check out the radar composite and infrared satellite from that night.


CIMMS (Cooperative Institute for Meteorological Satellite Studies

Here are a few stats from the meteorologists at our local NWS forecast office in Sterling, VA.  They have a thorough storm summary powerpoint you can view here. 

National Weather Service - Sterling, VA

Winds upwards of 70 mph brought down many trees, thousands were without power for days, and it was a long road to clean-up after the devastating storm. 

Fortunately, derecho's are not a common phenomenon in our area.  Here's a climatological derecho frequency graphic created by the Storm Prediction Center.  The SPC also has an extensive link on derecho's within the site.

SPC

It's one of those day's we'll all remember and a weather term we'll never forget.  I'll leave you with a link from the "Surviving Severe Weather" special the station aired last year.  Meteorologist Brian van de Graaff looks back at the infamous storm.

 

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Lightning safety awareness week: Local lightning detection

June 27, 2014 - 11:33 AM
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A few local golf courses have lightning detection systems, including Congressional Country Club, which is hosting Tiger Woods tournament the Quicken Loans National. With vivid lightning displays the other night which featured plenty of dangerous cloud-to-ground lightning, we wanted to re-post a video from our Surviving Severe Weather Special that aired last summer.

For your own lightning detection needs, there are a few places you can go. First, you can always download our Stormwatch 7 mobile app to your phone, which will send you a message if a dangerous thunderstorm is approaching. You can also check everything from our daily forecast, to our blogs and a radar map.

Another good app to have is the WeatherBug app, which has a an embedded feature showing you how close the nearest lightning strike is to your location. As of Noon on Friday when I wrote this blog, the closest strike was 332 miles away from my location. I think I am safe.

There are a few other places online you can go before heading out the door. Of course you can check our Live Doppler radar, but you can also check these lightning detection sites too.

Lightning Detection Map

D.C. Area Lightning Mapping Array

 

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