Archive for June 2013
The severe weather season in the Washington area has been unrelenting! Four tornadoes touched down in Maryland on June 10 and then three days later two more were confirmed. Reagan National had 2.77 inches of rain also on June 10th, which surpassed the former 24-hour rainfall record of 2.27 inches. There were NO daily record high temperatures set at either airport (Dulles or Reagan National).
Now that we are transitioning into the second month of meteorological summer, how do our odds stack up for severe weather? July leads the year with the most occurrences of high winds from thunderstorms, with an average of 92 reports across the region. Hail is less frequent in July with an average of 19 reports, compared to May, which leads the year with an average of 25.
Not such a good statistic here…. July averages the most tornadoes in the region, with 6. May, June and September tie for second place with an average of 4 tornadoes for each month.
Breaking down the severe weather coverage by hour, the least likely time for severe weather is 5 a.m.; 6 p.m. is the prime time for severe storms. Looking at the chart below, hail is most likely to occur between 4 p.m. and 5 p.m., damaging winds between 5 p.m. and 6 p.m. (21-22 UTC) and tornadoes in the 4 p.m. and 6 p.m. hours.
On our WJLA Severe Weather Special and in a previous blog, I showed cutting edge research regarding high wind tests at the Insurance Institute of Business and Home Safety (IBHS). Below is a look at a unique man-made hail storm intended to cause damage in order to better understand how to protect you and your home. It took the engineers at IBHS over a year and a half just to formulate the most realistic hailstone. Learn more and see the damage for yourself, here:
For last Friday's Severe Weather Special, Jacqui interviewed meteorologists at the Storm Prediction Center and found out how they issue watches and warnings for severe weather. They also revealed research that shows how cooler temperatures in May, such as those we experienced in Washington, may mean more severe weather in June and July.
As we enter the peak of severe weather season here in the Washington area, Jacqui helps you be better informed in this story:
We recently introduced you to David Hoadley of Falls Church, VA, who is considered the "Father of Storm Chasing." He has witnessed 222 tornadoes in his chasing career, and has some amazing stories to tell. He sat down with Doug Hill and talked live during our Severe Weather Special last Friday. There Hoadley talked about being under a mile from three fellow chasers that were killed by the El Reno EF5 tornado.
The pattern setting up late this weekend across the Washington metropolitan area is reminiscent of one a few summers ago at around the same time.
In late June 2006, a cold front approached the East Coast and then began to retrograde back to the west towards the Ohio Valley. This front was stretched out north to south and brought copious Gulf of Mexico moisture north as well as tapping plenty of Atlantic moisture.
Note the first image below; it shows a stationary front bisecting the region on June 24, 2006.
The upper level chart from late June 2006 shows a sprawling ridge in the West, which contributed to above average temperatures. The ridge was so persistent in June 2006 that Phoenix ended up with its warmest June on record with an average temperature of 94.6 degrees.
Even more striking, look at how the upper-level pattern is very similar to the setup we have now.
Now look at the next image showing the front retrograding west into the Midwest. This helped bring a surge of warm, moist Gulf of Mexico and Atlantic moisture into the region, helping to fuel very heavy rain.
Finally, look at the atmosphere profile similarity between the 2006 event and what is going on now. The dry air, evident by the far separation of the thick black lines at the 500 level (mid-levels of the atmosphere) on the second sounding below will become more saturated early next week as moisture returns in abundance. Winds are well-aligned in both profiles below and the amount of water, indicated by the PWAT number is very similar.
In all, this set up contributed to record rain across the District seven years ago in late June. Take a look at the daily record rainfall set across the Washington, D.C. – Baltimore corridor during this late June event.
While these numbers may not be achieved this time around, precipitation is already at a surplus for June and the year, so it won’t take much to push streams and creeks out of their banks and cause flooding in poor drainage areas as these strong downpours head our way.
This is the latest look at how much rain would be needed in 1 hour to produce flash flooding. Much of the region only needs 2.0 to 2.75 inches in 1 hour to cause flash flooding.
The heavier showers and storms could easily drop that much in an hour or less over the next few days. Be sure to never cross a flooded roadway because the water is typically deeper than it appears.
For the latest forecast, click here or tune to WTOP Radio for weather every 8 minutes, 24 hours per day.
A massive facility was constructed only three years ago in rural South Carolina where natural disasters are recreated to put homes and construction methods to the test. The Insurance Institute for Business and Home Safety (IBHS) conducts what they claim are the most realistic natural disaster tests to date. For our Severe Weather Special, which aired last Friday, I traveled to IBHS to gain insight into their research. See the destructive footage, and learn about inexpensive modifications to a home that can make a big difference against mother nature, here:
Lightning is one of the biggest weather killers and in the summer months is at its worst. So far this year in the U.S., 7 people have been killed by lightning, which is good stating that the 30-year average is 53. The threat still remains though, as lightning can be a killer even if the skies overhead are blue.
Just this week, 23 Boy Scouts and an additional 3 Scout Leaders were struck by lightning in New Hampshire. None of them were killed, but some suffered burns and a tingling sensation. The majority of lightning strikes aren't fatal, but major complications can happen afterward and affects can linger the rest of your life.
The D.C. area is no stranger to lightning deaths over the past few years, with a 12 year old boy struck and killed while leaving a little league game in 2009, two people struck on the same day in 2010, and a woman struck while waiting at a bus stop in 2007.
The easiest way to avoid being struck by lightning is to head inside as soon as you hear thunder. Stay away from windows or if you're outside and near a car, get inside the car. For those scouts, the best thing they could of done was try to get to a substantial shelter which may not have been possible. That's always a good reason to plan ahead on days with potential storms.
The safest place if stuck outside during a thunderstorm is away from tall objects such as trees and make yourself as small as possible. I even saw Bear Grylls do this once on an episode of Man vs. Wild.
Luckily for us, residents in the D.C. area are usually close to shelter or a vehicle. Our partner WeatherBug has actually developed a Lightning Detection System across the D.C. area, with one such system located at Congressional Country Club. It may get a lot of use over the next couple of days during the AT&T National Tournament! Check out how it's used in our Lightning Safety Segment of the Severe Weather Special last Friday.
As mentioned in a previous blog, for the next several days I'll be posting segments from our WJLA Severe Weather Special which aired last Friday. If you missed it on-air, you can catch some of the action online, so check back for unique severe weather stories.
Meet David Hoadley, the "Father of Storm Chasing," as he chats about his experiences tornado chasing and offers insight into the recent deaths of three fellow chasers. David was chasing the same tornado as those who perished. Doug Hill reports...
The summer solstice occurred last Friday, June 22nd and that was the last time the sun was perpendicular to the Tropic of Cancer. It was also the day in which we experienced the longest duration of daylight with a total of 14 hours 54 minutes. If fact we had a six day stretch of extended daylight. But today, things start to change. No you are not going to notice it right away – but in the DC metro region today we will experience only14 hours and 53 minutes of daylight.
Now that we have peaked on our daylight I thought it would be good to look forward to our shortest day of the year, the winter solstice, when the hours of illumination will be cut back a whopping 5 hours and 27 minutes! This translates to a loss of nearly 60% of our light over the span of about 6 months. That means only a measly 9 hours and 26 minutes of daylight light can be expected on the 21st of December. So it is gradual and hopefully easier to tolerate.
Now before you start to complain, keep in mind our friends in the upper northern most latitudes of Alaska. Located at the very top of the state, Barrow has a two-month winter period in which the sun doesn't rise at all! The sun is down for a whopping 67 days from November 18 to January 23. On the flip side the sun is up for 85 days for 24 hours straight from May 10 to August 2.
- courtesy alaskatravel.com
Quite a contrast and it must wreak havoc on their sleeping schedule. As an early to bed and very early to rise guy, I can say I look forward to earlier darkness! :)
In case you missed our ABC7 Storm Watch special "Surviving Severe Weather" last Friday, I'll be posting some of our segments over the next several days, so you don't entirely miss out on the action. Check back all week for more informative and sometimes lighthearted segments regarding severe weather, research, prediction and preparation.
We all remember the infamous derecho that struck Washington about one year ago. Here's the story of a local man, and his unique approach to the storm along with more background on derechos and how often they affect the D.C. area. Brian van de Graaff reporting:
Topics include everything from the devastating tornadoes earlier this year in Oklahoma, to the tornadoes last week in our area, as well as hurricanes, lightning, high heat, and the unforgettable derecho of 2012. Also, get a first hand look at a one of a kind natural disaster research center, and see what it's like to face 100+ mph winds.
These are just some of the topics discussed in the hour long special, which airs Friday night at 8 p.m. on ABC7.
- Find out what these are and how they can help protect you from severe weather
If you have any kind of questions about the weather during the special, be sure to ask us on our Facebook page or tweet to us. We will answer them as quickly as possible!
- Caskey felt tough until this pelted him with Category 3 winds
What a beautiful past few days we've enjoyed in the Nation's Capital. Slightly below average temperatures and low humidity. Who would have thought it was late June? And that the summer solstice was here?
The solstice occurs at 1:04 AM DST Friday, June 22nd. This is the time the sun is perpendicular to the Tropic of Cancer. It is the longest day of daylight and marks the celestial start to summer. Sunrise tomorrow morning is at 5:43 AM and sunset at 8:37 PM. That's a total of 14 hours 54 minutes. We couldn't ask for a better 'longest day of daylight' with sunshine, low humidity, and comfortable temperatures forecast for tomorrow.
To help visualize what happens on the solstice, take a look at the diagram below. The earth revolves around the sun along an imaginary axis. Notice the earth is tilted (23.5°). The solstice occurs at the time the sun is directly over the Tropic of Cancer, which is at 23.5°. For every place North of the Tropic of Cancer, the sun is at its highest elevation - directly overhead at high noon.
For the Northern Hemisphere, the summer solstice means the start of summer, whereas in the Southern Hemisphere the solstice marks the start of the winter season (the Earth is titled away from the sun, so less daylight, which leads to cooler temperatures). The reason we have seasons is because of the tilt of the Earth's axis. It also has to do with the amount of daylight and the atmospheric path length.
You may wonder, if the sun is at it's highest elevation at noon on the solstice and we have the longest hours of daylight, why it isn't the hottest day of the year, too. The main reason is because it takes much longer for the sun to warm the ocean, which absorbs and radiates the sun's energy over time. Typically, the hottest days occur in July and August. The deep, ocean water takes much longer to heat compared to the land. You also have to remember the Earth is made up of about 70% water. With all that water, it's going to take longer to warm up and, in turn, give us our hottest temperatures of the year based on the moderating effects of the ocean waters.
The amount of daylight will now slowly decrease until the winter solstice. The sunrise/sunset times surrounding the solstice, though, only fluctuate by a few seconds, so enjoy the added daylight and time outdoors!
NASA is looking forward to this weekend's supermoon. That's when the moon appears bigger and brighter because it's the closest it will be to earth all year.
Adam Caskey visited Goddard Space Flight Center in Greenbelt Tuesday morning. Dr. Michelle Thaller, a NASA Scientist says the moon will appear about 14 percent larger and 30 percent brighter than a typical Full Moon does.
The Moon will be at its closest distance to the Earth at exactly 7:32 a.m. on June 23, but you can still see it on the night of the June 22 as well.
Supermoons occur when the moon reaches the lunar perigee - its closest point to the earth on its elliptical orbit around Earth. Eileen Whelan pointed out last year that the Earth's perigee is about 50,000 kilometers closer to our planet than its apogee, which is the moon's longest distance from Earth.
In 2012, a supermoon was able to be seen on May 6, and a 2011 supermoon was visible on March 19.
Climate statistics for the month of May and the Spring months of March through May were released in the latest State of the Climate report. The D.C. area was actually slightly above normal temperature-wise for the month of May because of the three 90 degree days to end the month. Otherwise, it was a very changeable month with high temperatures in the 80s one week and 60s the next. Reagan National even recorded two days with lows in the 40s on the 24th and 25th of May, which was the latest such period of temperatures that cool in over 30 years.
Above is a look at the Spring temperature ranks for the United States. Much of the U.S. experienced its top 10 coolest Spring on record from the upper Midwest to the Southeast. The D.C. area was slightly closer to normal for temperatures and the Western U.S. including California and Arizona were well above normal.
See the full report here: NOAA National Climatic Data Center, State of the Climate: National Overview for May 2013
Overall, this was the coolest Spring period since 1996, and the 38th coolest Spring on record.
The above-average precipitation and below-average temperatures in the north-central United States were associated with a spring snow cover extent that was above average. According to data from the Rutgers Global Snow Lab, the spring snow cover extent was the eighth largest on record and the largest since 1984.
According to the report, temperatures for the year are now averaging 0.2 degrees C above normal. Although temperatures are still cooler than average for the year for much of the Midwest, Plains and Southeast states, near-normal to above average temperatures have been noted through the rest of the country.
As far as precipitation, it has been both good and bad. Record precipitation across the Midwest has caused flooding along many rivers including the Mississippi and Illinois Rivers. On the otherhand, California has been experiencing its driest month on record which has contributed to conditions enhancing the threat for forest fires. The Drought Monitor below continues to show exceptional drought for much of the western Plains and through the Southwest though areas along and east of the Mississippi are in good condition entering summer.
National Weather Service meteorologist Andrew Woodcock mentioned it this morning in his forecast discussion, and it got me thinking, so I dug a little deeper to compare the past five Junes, and I wanted to take a peek at the long range forecast for the rest of this month.
So far this June at Reagan National Airport (DCA), there have been only two 90 degree days with the warmest temperature being 91°. Compare that to 2012 when there were three 90 degree days by the 17th, but there were eight during the second half of the month for a grand total of eleven. Also, keep in mind that there was some serious heat during June 2012 with the warmest reading being 104° on the 29th.
Below is a table of the previous 5 Junes. Of note: June 2010 had eighteen 90 degree days, so over half the month featured highs at or above 90° with a maximum temperature of 100° on the 24th. Conversely, what a relief June 2009 was with only two 90 degree days and a maximum of a mere 91°.
- June Comparison
So what’s ahead for the rest of the month? Well, for the rest of this week, I think we’ll have only one shot at a 90 degree day, and that’ll be tomorrow. Also, Sunday and into the final week of June I think we have the potential to come close to 90° for a few more days, and should DCA hit 90°, I doubt it’ll exceed it by much. The Climate Prediction Center has the D.C. area within an increased chance of above average temperatures through the end of June, but no major heat seems to be in the works for the final two weeks of June for the Washington area. That doesn’t mean that it’ll be cool with below average temperatures – I’m just looking at 90 degree day potential.
The statement below was issued on Friday from the National Weather Service office in Sterling, VA. Additional surveys may be released at some point today discussing the Saint Mary's County tornado as well as the survey of the damage in the Thornburg, VA area.
...Public Information Statement...
Long track tornado confirmed through Montgomery County, Maryland.
One additional tornado confirmed in Saint Mary’s County, Maryland
One investigation continues in Spotsylvania County
One long track tornado has been confirmed through Montgomery County. A second tornado was confirmed in Saint Mary’s County affecting the Coltons Point area. A third area of wind damage is still under investigation near Thornburg, Virginia.
The Montgomery County tornado report follows. The Saint Mary’s tornado
report will be available on Monday as the survey team is still working on the details. The Thornburg event will also be detailed on Monday.
The National Weather Service in Sterling expresses its appreciation
to those who assisted in conducting surveys and provided information
used during the surveys...including members of the emergency management...skywarn storm spotters...and members of the public affected by these storms.
...Tornado confirmed in Montgomery County, Maryland...
Location...North Potomac to Burtonsville in Montgomery County, Maryland
Date...June 13 2013
Estimated time...3:41 pm EDT to 3:59 pm EDT
Maximum EF-scale rating...EF-0
Estimated maximum wind speed...75 mph
Maximum path width...150 yards
Path length...17.3 miles
Beginning lat/lon...39.091N / 77.269W
Ending lat/lon...39.108N / 76.947W
* The information in this statement is preliminary and subject to
change pending final review of the event(s) and publication in
NWS storm data.
Eyewitness accounts...radar imagery...and a ground survey concluded
a long track EF-0 tornado occurred in Montgomery County, Maryland
on the afternoon of June 13th 2013. Peak winds were estimated at
75 mph. Damage was almost entirely from downed trees. In that
regard numerous homes and a few parked vehicles were damaged by
trees falling onto them. No injuries have been reported.
First consistent damage was noted near the intersection of Turkey Foot Road and Jones Lane in southwest Montgomery County near North Potomac, Maryland where a few large trees were over the road. The tornado raced east nearly 60 mph to the northern section of Rockville,
Maryland. At least 14 homes were significantly damaged by uprooted
As it continued east to the Norbeck and Aspen Hill area 30 trees were uprooted in the Manor Country Club Golf Course as well as numerous homes damaged in the surrounding communities from tree damage. Tree damage was noted along the Intercounty Connector Route 200 at the Layhill Road exit. Finally a few trees were downed in Spencerville and Burtonsville.
Based on the damage, this tornado is rated EF-0, with estimated wind speeds of 75 mph. The 17.3 mile damage path length was covered in 18 minutes and had consistent small branch damage with occasional areas with significant tree damage.
Additionally there was a parallel 7 miles path of damage through south
Rockville and Glenmont, Maryland with similar tree damage. This area was found to be straight line winds from the outflow just south of the tornado from the parent supercell storm.
The National Weather Service would like to extend its thanks to Montgomery County Fire who confirmed the tornado on the ground during the storm and Montgomery County Emergency Management who provided invaluable assistance during the ground survey.
Severe thunderstorms were reported throughout the D.C. area yesterday with the strongest in the afternoon hours. These storms caused wind damage throughout the region and more tornadoes were reported just 4 days after the last event on Monday. What an active week!
A tornado was reported by the fire department in Norbeck in Montgomery County as it crossed Norbeck Rd. and Georgia Ave. In addition, funnel clouds were reported by trained weather spotters in Spotsylvania County, another in Loudoun County near Countryside by the Sterling Fire Department, and one more at BWI Thurgood Marshall estimated to be a few miles away.
I came across this video on youtube of a timelapse of the storms yesterday. Apparently this was taken near Columbia, MD and there possibly is a funnel around the 1:06 mark. I'm not sure how authentic this is but is worth taking a look at anyways because of the great timelapse.
This is what the publisher wrote about the timelapse below.
Published on Jun 13, 2013
Filmed a time-lapse of today's severe thunderstorm, and captured the Olney-Colesville tornado zipping by at 1:06. I can't confirm 100% that it is the tornado but it appeared exactly where and when it should have given the NWS warning a few minutes prior.
Later in the video you can see the bow shock and fast-moving winds that spawned a tornado in Rockville, MD.
Tornado or not, still a beautiful storm and an exciting day for storm-spotting in Maryland - enjoy!
5:53pm: Our WeatherBug station reports 1.24" of rain in Columbia, MD, 1.2" in Jessup, 1.11" in Hamilton and 1.04" in Germantown.
5:52pm: A Flood Warning is in effect until 9:45pm for Anne Arundel, Loudoun, Montgomery, Howard and Baltimore Counties. Recent rainfall of 1-2 inches will cause rises on some creeks and rivers.
5:49pm: Unfortunately for some, now it is time to pick up the debris left behind. Here is one example from Lexington Park, MD from Dawn Elliott of a large tree down in her backyard.
5:19pm: Here is a link to all of the local storm reports from the National Weather Service office in Sterling, VA which issues the watches and warnings for the D.C. area.
4:49 p.m.: Most of the major alerts and warnings have been canceled for many parts of the D.C. area, but the storm is making its way toward the Eastern Shore.
The Bay Bridge has been closed in both directions while the storm pushes through.
4:33 p.m.: Power outages are becoming a major problem for the entire area, with tens of thousands regionwide in the dark. Follow the latest numbers and find out who to call for help here.
4:22 p.m.: Passengers and staff at BWI Airport near Baltimore have been ordered to take shelter away from windows due to the severe storms.
4:17 p.m.: The National Weather Service says that confirmed tornadoes have touched down today in Laurel and Olney.
4:16 p.m.: Tornado Warnings continue to exist in portions of Anne Arundel, Prince George's and Montgomery counties.
If a tornado warning is issued, take cover in an interior room on the lowest floor of the building you're in.
2:35pm: A Tornado Warning is in effect just south of Fredericksburg, VA for Spotsylvania County in VA until 3pm. A funnel cloud was reported with this storm located 3 miles west-southwest of Fredericksburg and just west of I-95. The warning is in effect until 3pm.
2:06pm: Severe T-Storm Warnings are in effect until 3:15pm for the northern Shenandoah Valley. Storms are headed towards I-81 with possible gusts to 60mph.
Another area of severe storms are just southwest of Frederickburg in VA. These storms are capable of producing large hail and damaging winds.
1:51pm: The next line of storms is approaching the I-81 corridor as it exits the mountains and enters the Shenandoah Valley. Severe T-Storm Warnings are posted for severe winds and large hail. Be sure to keep an eye on Live Doppler Radar as these storms move into the region from the west.
12:28pm: A Severe T-Storm Watch is in effect until 7pm for the majority of the D.C. area. Damaging winds, large hail and an isolated tornado may be possible during the afternoon hours so be sure to stay tuned to the latest severe weather alerts.
12:07pm: Skies are beginning to clear ahead of the next line of storms. This will lead to added instability with additional heating and will help fuel these storms as they pass east of the Appalachian Mountains.
11:54am: A new Severe T-Storm Watch will be issued soon for the D.C. area and points south. In addition, a Moderate Risk for severe storms will also be placed over portions of North Carolina. The Mesoscale Discussion can be found here.
11:39am: Temperatures are on the rise into the low 80s around D.C. and south but still in the 70s with some stratiform precipitation and clouds lingering around the northwestern suburbs. Winds are currently breezy out ahead of the trailing cold front moving into West Virginia. Conditions for lunch will be fine so no worries about storms over the next hour.
- HRRR Model showing forecast composite reflectivity this afternoon
A severe line of storms is moving into WV and is expected to reach the D.C. area later this afternoon between 2pm and 6pm today but may linger even later as they cross the D.C. metro. Models are expecting a line a storms to develop west of D.C. and move east towards the Metro and I-95 corridor south of D.C. Storms may again feature damaging winds and large hail, though a weak tornado may not be out of the question as well.
This system is already developing strong storms over the mountains that I am concerned will continue to intensify once they get east of the Blue Ridge into a more unstable airmass. We'll keep you posted.
9:51am: Storms have weakened as they moved into the D.C. area. It looked as if outflow came through ahead of the storms and took away some of the strength from the line. The Severe Thunderstorm Watch has been cancelled for the majority of the D.C. area besides Calvert and Anne Arundel Counties which will follow shortly.
More storms are developing west of the D.C. area, with the strongest in Ohio and West Virginia. This is the area we will watch for additional development through the early afternoon. Severe storms will continue to be possible through the afternoon hours, and the D.C. area is still under a Moderate Risk for severe weather today.
We are still expecting more storms to fire this afternoon as some clearing is already being noted across parts of the D.C. area. This will help to destabilize the atmosphere, which doesn't need much more destabilization given the already strong dynamics as the area of low pressure and associated shortwave trough approach the reagion from the west.
Numerous showers and storms are expected to affect the D.C. area between 2pm and 6pm and another Severe Watch with Warnings will be possible. The storm activity later today has to potential to be stronger than what the region saw this morning, so don't let your guard down just yet. We will keep you aware of the latest developments through the day so you stay a step ahead of the game.
9:28am: Severe T-Storm Warning in effect for Prince Georges County and Anne Arundel through 10:15am. The majority of this storm is already out of Prince Georges County and the hardest hit areas will be in Anne Arundel from Annapolis and points north. This line will affect the Bay Bridge east to Kent Island and the Delmarva.
9:22am: Storms are rolling through the D.C. Metro currently and will be through the city over the next 30 minutes or so heading into Prince Georges County and Southern MD. Radar Here (Hit Control and F5 at the same time to refresh)
8:48am: Don't forget to check out our HD weather cameras, they are showing some pretty gnarly skies right now!
8:34am: Here are two pictures from Megan Bower. One near Woodstock, VA (top) and the other near Strasburg, VA (bottom).
- Shelf Cloud near Woodstock, VA
- Near Strasburg, VA
8:26am: Storms are beginning to enter Leesburg in Loudoun Co., VA as well as extreme western Montgomery Co. in MD. Damascus, Mt. Airy and Clarksburg will all be affected soon. Another strong storm is located in Western Fauquier County moving east towards The Plains, VA along I-66.
8:11am: Quarter to Half Dollar sized hail was reported in Libertytown, MD in Ferederick County.
8:04am: A tree has been reported down in Washington Co., MD near Keedysville from emergency managers.
8:03am: A Severe T-Storm Watch continues through the Eastern Shore as well through 11am.
7:49am: A Severe T-Storm Warning is in effect for Frederick in MD, Carroll, Washington, Berkeley and Jefferson Counties may have damaging winds up to 70mph and hail to the size of half dollars! The strongest part of this line is in Northern Frederick County in MD.
7:36am: A Severe T-Storm Warning is currently in effect for Frederick, Berkeley, Jefferson and Washington Counties until 8:15am. Winds in excess of 60mph are possible in this line of storms.
7:28am: A Severe Thunderstorm Watch is in effect through 11am this morning as a line of thunderstorms moves towards the D.C. Metro area. Damaging wind gusts will be the primary threat in this line of storms as it moves through the D.C. area by 10am. The Watch covers the majority of the D.C. area besides Stafford County and south in VA and St. Marys County in MD.
After strong storms ripped through the area on Monday, 3 tornadoes confirmed, another round of severe weather is possible Wednesday and Thursday.
The Storm Predicition Center has the the D.C. area under a Slight risk for severe storms both days. What does this mean? There is an elevated risk (15%) for damaging wind gusts, hail, and isolated tornadoes. The areas shaded in red, in the Ohio Valley, are under a moderate risk for severe weather Wednesday, which means probabilities for severe are between 30% and 45%.
- Storm Prediction Center
By Thursday, D.C. remains under a Slight risk for severe storms, as a weather system strengthens and pushes East. This is the convective outlook for Thursday.
- Storm Prediction Center
Atmospherically, a surface and upper level frontal system will track along the north central Plains into the Midwest and Ohio Valley Wednesday. With very high heat and humidity, coupled with strong winds aloft, the potential exists for a severe weather outbreak.
Even though strong thunderstorms are possible late Wednesday around the DC metro, the higher probability of severe weather arrives Thursday with more atmospheric dynamics at play. Take a look at the 500mb vorticity on Thursday afternoon.
The pink/white colors indicate high speed and directional shear, as an area of low pressure rapidly deepens and develops over northeast Maryland and Pennsylvania. Here's another view of the setup at different levels of the atmosphere on Thursday afternoon. Notice the precipitation field in the top right corner, as well as surface wind speed on the bottom left corner.
I highlight Thursday, as I think the dynamics are more inclined to enhance the severe weather threat in the D.C. area. There will be plenty of heat and humidity on Wednesday for strong and potentially severe thunderstorms to fire up. The forcing will be more prevalent on Thursday, but on both days it will be critical to monitor the changing weather situation.
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