1915 posts categorized "Television"

04/26/2017

A Steamy and Stormy Weekend! Update on Severe Threat.

Following a nice start to the week, our weather gets active again as we head into the weekend with a round of showers expected late tonight and into tomorrow morning.  

Fortunately, this first round is expected to be sub-severe and fairly light with most areas picking up less than a quarter inch of rain.  Showers look to exit by afternoon behind a cold front that looks to drop temps back to near 70 for a high on Thursday.  

While Thursday night and most of the day on Friday appear to be quiet, as a strong low develops over the Southern Plains, a warm front will push into our region bringing a surge of warmth and moisture and the potential for strong storms as we head into Friday night.  

Friday Night

AdvanceTrak 5

While the Storm Prediction Center keeps the "greatest risk" (an enhanced risk in this case) to our west, they have placed much of the Lower Ohio Valley, including our viewing area, under a Slight Risk for severe storms late Friday and Friday night.

A quick analysis of the data shows that the wind profile would be sufficient for strong to severe storms and the warm front is expected to serve as the focus for storm development.  

However, instability may be limited for parts of our area with the GFS showing CAPE (convective available potential energy) on the order of 1,000 units or less for most of Southern Indiana.  CAPE does ramp up for our Kentucky Counties  with perhaps a better chance for seeing a few damaging wind or hail makers into the overnight on Friday night.

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Let's time it out with AdvanceTrak...

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AT shows most of the storm development late Friday evening and overnight before diminishing by morning.  

This seems to be in line with what most of the "synoptic" models are showing (i.e., the GFS/EURO) and could cause issues for the Great Balloon Race Saturday morning. 

As far as severe potential is concerned, I think it will be limited to areas along and south of the river with the main threats being hail and wind.  

Saturday/Saturday Night

Gfs cape2

Moving ahead into the day on Saturday, a surge of warmth and low level moisture will make it feel very summer-like.  This "juiced" atmosphere with temps well up into the 80's will increase instability for the entire area giving us expected CAPE values on the order of 1,000 - 2,500 units.  This would be more than enough to fuel thunderstorms.  However, we will be lacking a "trigger" or forcing mechanism to get storms started as the warm front will have lifted north into Central Indiana by Saturday afternoon.

Gfs sfc01

This means that after the morning round of showers/storms, we will be mainly dry through the afternoon hours on Saturday. 

That could change Saturday night with model data indicating that scattered showers/storms will develop late as the "low level jet" (wind flow a short distance above the surface) increases helping to aid in the development of "elevated" as opposed to surface based storms.  

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While a few of these could be strong, a lack of instability during the overnight should mitigate any real severe threat. 

Sunday/Sunday Night

Moving ahead into Sunday, the Storm Prediction Center keeps the Slight Risk (15% risk area) to our west/south.

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The slow moving storm system to our west approaches and deepens producing strong storms into the Lower and Middle Mississippi River Valley during the day on Sunday.

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Ahead of this storm we will see a strong southerly flow and good heating which may help to increase instability.

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This could set us up with a west to east moving squall line of storms Sunday evening/Sunday night.  

Analyzing the data we see that because of a significant warm layer of air aloft, instability might be mitigated some with the GFS showing around 1,000 units of CAPE for most of our area late day Sunday.

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While this is on the lower end of what you would expect for severe storms, it might be enough when combined with a ROBUST wind field that develops in response to the approaching low with the GFS showing 70+ knot winds a short distance above the surface (at 850 mb level).  

Gfs 850 wind

So what do I think?

I think that heavy storms are likely for much of the area Friday night and a few severe storms will be a possibility especially if they get going into our Southern Counties where instability will be maximized.  Overall I think the tornado risk is low with this set up though.  

Despite the Storm Prediction Center forecast, there could be a legitimate severe threat Sunday evening if the squall line arrives near peak heating.  The later it comes in, the lesser the threat.  However, considering the amount of wind energy aloft, it might be able to overcome less than impressive instability.  Damaging winds would be the main threat.

The other factor to consider this weekend is just how much rain will we see?  While the GFS keeps the heaviest stuff to our west into the Middle Mississippi River Valley, rainfall totals of 2 to 4 inches, if verified, could cause some flooding concerns. 

Gfs precip total

That's a lot of rain!  We'll be watching.  

WDRB Meteorologist Jeremy Kappell

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04/25/2017

NOAA: 2017 U.S. tornado season off to a whirlwind start

The 2017 tornado season across the United States has gotten off to an active start. As of April 17, 570 tornadoes have been reported (preliminarily), which is almost a hundred more than average. The season jumped out of the gate with an incredibly active January: 134 tornadoes in total—more than triple the long-term average—and an especially radical departure from the past three years, during which the average number of January tornados was just 16.

Tornados_2017todate_620

The image above shows the running tally of preliminary tornado counts in 2017 (gold line, through April 22) compared to the 2005-2015 average (beige bars). The data were provided by Patrick Marsh of NOAA’s Storm Prediction Center. As the daily numbers add up, the line rises like an irregular staircase, with this year far steeper than normal. The graph is overlaid on a picture of a tornado looming over a farm in Benton County, Minnesota, on August 24, 2014.

Severe weather encompasses not only tornadoes, but also thunderstorm winds faster than 58 miles per hour and hail larger than three-quarters of an inch in diameter. Severe weather is at a relative minimum during the winter months, as you can see in this animation of the historical probability of severe weather. When it does occur, the highest likelihood is for it to be somewhere across the southeastern United States. As winter ends and temperatures warm, the highest activity for severe weather begins to shift north and westward towards the southern Great Plains and Tornado Alley.

As mentioned above, much of the early tornadic activity in 2017 was focused across the Gulf Coast states, especially Georgia. Why does severe weather tend to occur across the Gulf Coast during winter? For tornado-producing thunderstorms to form, they need moisture, an unstable atmosphere that lets air rise easily, and something to force the air up in the first place. During winter, when much of the country is cold and dry, the Gulf Coast states can remain warm and moist due to the nearby Gulf of Mexico, which holds onto its summer warmth longer than the atmosphere. When the warmth and moisture combine with winter storm systems that can be found racing along the jet stream across the southern tier of the United States, thunderstorms—some severe—can be the result.

By spring, as warm air begins to re-invade the country, the jet stream—an area of fast moving winds high in the atmosphere that serves as a storm highway and reflects a boundary of cold air to the north and warm air to the south—begins to move north. As warm and moist air which originates over the Gulf of Mexico penetrates farther into the interior of the United States, the locations with the highest chance for severe weather begins to shift northward and westward to the aptly named Tornado Alley.

As for the current tornado season, with a preliminary total of 558 tornadoes, the 2017 season is already more than halfway to the seasonal total of just a year ago. However, an overactive start to the tornado season doesn’t mean it will stay that way. (The flip side is also true: even a season that is slow to start may wind up being unusually active by the time it’s all over.) Regardless of seasonal totals, the way to stay safe is to be ready for any severe weather event, so pay attention to the latest forecasts from NOAA’s Storm Prediction Center and your local National Weather Service office for any severe weather updates.

Image and information courtesy NOAA

WDRB Meteorologist Jeremy Kappell

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04/24/2017

NASA: A New Angle on Two Spiral Galaxies for Hubble's 27th Birthday

In celebration of the 27th anniversary of the launch of NASA's Hubble Space Telescope on April 24, 1990, astronomers used the legendary telescope to take a portrait of a stunning pair of spiral galaxies. This starry pair offers a glimpse of what our Milky Way galaxy would look like to an outside observer.

Hubbleimagestscihp1714af6576x7614Hubble Space Telescope images of spiral galaxies NGC 4302 (left) and NGC 4298 (right) in visible and infrared light. Credits: NASA, ESA, and M. Mutchler (STScI) A New Angle on Two Spiral Galaxies for Hubble's 27th Birthday | NASA

The edge-on galaxy is called NGC 4302, and the tilted galaxy is NGC 4298.

These galaxies look quite different because we see them angled at different positions on the sky. They are actually very similar in terms of their structure and contents.From our view on Earth, researchers report an inclination of 90 degrees for NGC 4302, which is exactly edge on. NGC 4298 is tilted 70 degrees.

In NGC 4298, the telltale, pinwheel-like structure is visible, but it's not as prominent as in some other spiral galaxies. In the edge-on NGC 4302, dust in the disk is silhouetted against rich lanes of stars. Absorption by dust makes the galaxy appear darker and redder than its companion. A large blue patch appears to be a giant region of recent star formation.

Hubblegalaxies2(CLICK ON IMAGE TO ANIMATE) This animation zooms through the Virgo Cluster of nearly 2,000 galaxies into tight Hubble Space Telescope images of spiral galaxies NGC 4302 (left) and NGC 4298 (right) in visible and infrared light. Located approximately 55 million light-years away, the starry pair offers a glimpse of what our Milky Way galaxy would look like to an outside observer. Credits: NASA, ESA, and G. Bacon, J. DePasquale, and Z. Levay (STScI) Acknowledgment: A. Fujii; Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO; B. Franke (Focal Point Observatory); and M. Mutchler (STScI)

Both galaxies are approximately 55 million light-years away. They reside in the constellation Coma Berenices in the Virgo Cluster of nearly 2,000 galaxies. Both were discovered in 1784 by astronomer William Herschel. Such objects were first simply called "spiral nebulas," because it wasn't known how far away they were. In the early 20th century, Edwin Hubble discovered that galaxies are other island cities of stars far outside our Milky Way.

A typical spiral galaxy has arms of young stars that wind outward from its center. The bright arms are regions of intense star formation. Such galaxies have a central bulge and are surrounded by a faint halo of stars. Many spiral galaxies also have bars that extend from the central bulge to the arms.

The edge-on NGC 4302 is about 87,000 light-years in diameter, which is about 60 percent the size of the Milky Way. It is about 110 billion solar masses, approximately one-tenth of the Milky Way's mass.

The tilted NGC 4298 is about 45,000 light-years in diameter, about one third the size of the Milky Way. At 17 billion solar masses, it is less than 2 percent of the Milky Way galaxy's 1 trillion solar masses.

The Hubble observations were taken between January 2 and January 22, 2017 with the Wide Field Camera 3 (WFC3) instrument in three visible light bands.

The Hubble Space Telescope was launched aboard the Space Shuttle Discovery on April 24, 1990 and deployed into low-Earth orbit the next day. From its perch high above the distorting effects of Earth's atmosphere, Hubble observes the universe in near-ultraviolet, visible, and near-infrared light. Over the past 27 years, the space telescope's breakthrough discoveries have revolutionized the fields of astronomy and astrophysics.

For more information about this galaxy pair and Hubble, visit: www.nasa.gov/hubble

Information Courtesy NASA

WDRB Meteorologist Jeremy Kappell

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04/23/2017

Pesky Low Departs... Summer-like Temps to Follow!

Pesky area of low pressure over the Southeast continues to influence our weather with clouds, cool temps and even a few showers this evening.  

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However, eventually, high pressure located off to our west will build in over the next couple of days with the return of sunshine and MUCH WARMER conditions.  

Let's time it out with AdvanceTrak...

AT shows clearing over Southern Indiana out the door with temps in the 40's.  Lower 50's into Kentucky with clouds remaining.  

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The solid overcast should give way to a sun cloud mix by afternoon with more sun across Southern Indiana and more clouds into Kentucky.

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Temps warm back into the lower 70's for areas that receive more sunshine.

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The warming trend looks to continue into the middle of the week.

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Following temps near 80 on Tuesday, middle 80's look to return with a strong south wind on Wednesday.  

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Beyond that, it looks like we are looking at a few rounds of showers/storms Wednesday night through Friday night.

If data holds true, we could be looking at temps NEAR 90 next weekend!!  

Jude has a full update first thing in the morning on WDRB News. 

WDRB Meteorologist Jeremy Kappell

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04/22/2017

Glass Half Empty or Full Sunday?

Following an improving day for Thunder Saturday, it will be a glass half full or glass half empty day on Sunday, depending on where you live as a slow moving frontal system drifts to the south over the next 24 hours with clouds and rain chances south of the river and sunshine/warmer conditions north.

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Let's time it out with AdvanceTrak...

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We're expecting a BIG warm up next week with temps returning to the 80's!  Katie has a full update first thing on WDRB in the Morning.

WDRB Meteorologist Jeremy Kappell

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04/18/2017

The Four Types of Thunderstorms... and the Dangers they Pose!

On average, Kentuckiana recieves approximately 45 inches of precipitation per year and while some of that falls as sleet or snow, most of it comes in the form of rain.  

Of the rain that falls, most of it occurs during thunderstorms during the spring and summer months.

There are several types of thunderstorms, but each of them starts out the same.  As cumulus clouds! 

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These cumulus clouds grow as moisture laden parcels of air rise, expand and cool causing water vapor to condense into cloud droplets/ice crystals and then eventually into precipitation.  These areas of rising air are called "updrafts" and essentially are what feed the storm.  

Once precipitation begins to fall, it carries a doward momentum of air with it known as the "downdraft".  The harder the rain/hail, the stronger the downdraft.  The downdraft is what you feel when a storm blows in "rain cooled air".  

However, this downdraft mechanism is also what essentially kills the storm.  You see, in the case of the typical "summertime thunderstorm" the updraft that creates the thunderstorm eventually gets overtaken by the downdraft and it runs out of fuel.  

Ordinary

This is the basic life cycle of the thunderstorm and a typical storm will form and then fall apart within an hours time.  

Single Cell Thundertorm

When a thunderstorm updraft goes up and then straight back down, as illustrated in the diagram above, it is known as a SINGLE CELL thunderstorm..  Also known as "pop up" or "popcorn" storms, these are very common during the heating of the day during the late spring or summer months.

Towering-thunderstorm

The single cell thunderstorm can bring brief heavy rain, small hail, gusty winds and dangerous lightning.  They also have the ability to bring quick relief from intense summertime heat!

Multi Cell Thunderstorm

Often times, single cell storms will combine and interact with other single cell storms to form a MULTI CELL thunderstorm.   

Thunder storm types

Multi cell storms are also very common during the spring and summer months.  In addition to bringing the risk of gusty winds, small hail and lots of lightning, these storms are capable of dropping a tremendous amount of rain over a short period of time especially when they "train" or line up moving continuously over the same areas.  This can lead to flash flooding.

Fountain Square Apts in Highview  Photo credit Scott Utterback

Squall Line Thunderstorm

Another common, and often times dangerous, type of a thunderstorm is the SQUALL LINE. 

A squall line is a large line of intense thunderstorm activity that can stretch across hundreds of miles of real estate.  These storms are common here in Kentuckiana especially during the spring and summer months and although they are capable of producing very heavy rain, lightning, hail and even quick spin up tornadoes, their biggest threat usually comes in the form of wind!

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Squall lines often produce winds in excess of 60 mph and have been known to produce wind gusts to over 100 mph!  They can be more damaging than even strong tornadoes because of their size that the amount of area they can affect.

When they become particularly strong, they are called a "derecho" which means widespread wind storm in Spanish. 

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The squall line can be easily identified on radar as well as the cloud structure.  The above image features a rather large and ominous looking "shelf cloud" which forms just ahead of the squall line.  

The shelf cloud forms in the presence of high speed downdraft winds that race out ahead of the heavy precipitation.  

The Supercell Thunderstorm

The other main type of thunderstorm is the supercell.  Fortunately, the supercell is also the least common because it is potentially the most severe of all thunderstorms.  

Tornadic_supercell

The supercell is characterized by having a rotating updraft.  This rotating updraft allows the storm to live much longer than normal single cell or mutli-cell thunderstorms and it also allows it to become more organized.  

On radar, the supercell often looks like a kidney bean and sometimes can display a "hook echo" pattern which can be an indicator that a tornado could be occuring.

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Like the Henryville EF-4 from March 2012, almost all violent or strong tornadoes form from supercell thunderstorms.

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In addition to tornadoes, they are also capable of producing extremely large hail, destructive winds, extreme lightning and flash flooding.  

WDRB Meteorologist Jeremy Kappell

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04/17/2017

THUNDER FORECAST: Rain Likely. Heavy Storms Possible!

While still several days away, confidence is growing on a wet forecast for Saturday.  Of course this is not good news for Thunder Over Louisville and the kick off to the 2017 Kentucky Derby Festival.  

The Storm in Question

Gfs jet

The storm is currently located over the North Pacific revolving over top of some high speed jet stream winds that are just now beginning to come onshore the West Coast.

By Friday the core of these upper level winds are expected to eject out of the Rockies and into the Southern Plains helping to develop a surface low over West Texas.  From there, the low is forecasted to deepen as it travels towards northeast and eventually into Kentuckiana by late Saturday and Saturday night.  

Let's time it out with the current run of the Euro...

The 12z run of the Euro shows an area of low pressure approaching out of Northern Arkansas with a large shield of rain extending into the Lower Ohio Valley Saturday morning.

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Widespread rain continues locally with thunderstorms developing near the low across the Middle Mississippi River Valley early Saturday afternoon.

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The low deepens arriving near Evansville by early evening with very heavy rain/storms approaching our area.

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The low travels right over our area Saturday night as widespread rain and storms continue.

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By morning on Sunday the bulk of the rain shifts east into Appalachia with wrap around showers locally.

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If the Euro is correct, then it rains all day Saturday and Saturday night potentially falling heavily at times with lightning and thunder.  This would mean that both the air show and the firework display would be negatively impacted.  In fact, it's possible that parts, if not all, of the air show could be cancelled due to low cloud "ceilings".  

What do I think?  

Unfortunately, I think the Euro might have the right idea.  This is a pretty classic set up for us this time of the year with a deepening Southern Plains low traveling northeast along an existing frontal boundary.  This would give it the ability to pull up abundant moisture over top of a strong "baroclinic zone" or tight temperature gradient presumably located over our area.  The latest run of the GFS supports this solution with the potential for heavy rain and storms especially late in the day.  

Is severe weather possible? 

The short answer to that is yes, it's possible.  However, a more likely scenario keeps surface temps too cool, likely in the 60's, for much of a severe threat in Louisville.  However, this doesn't reduce the potential for very heavy rainfall and thunderstorms.  

So how much rain?  

Data from both the Euro and GFS suggest that we could see widespread 1 to 2 inch rainfall amounts Saturday.

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Moral of the story... while I wouldn't cancel your Thunder Plans at this range, I would start preparing for what could turn out to be a very wet Saturday.  

Marc and Rick have your update on WDRB News this evening.

WDRB Meteorologist Jeremy Kappell

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04/16/2017

The Storm Prediction Center Monitoring Severe Risk

The Storm Prediction Center has issued a Mesoscale Discussion on the potential for strong storms in our area late this afternoon/evening.  Here is there discussion...

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SUMMARY...Isolated strong to damaging winds and perhaps marginally severe hail may occur with thunderstorms across this region through the afternoon. Watch issuance is unlikely owing to an overall marginal severe weather threat.

DISCUSSION...Scattered to numerous thunderstorms are ongoing across this region as of 1855Z along a pre-frontal trough extending from northeast to southwest across the OH Valley, and with renewed development in southeastern MO/northeastern AR along part of a MCS that formed overnight across the southern/central Plains. The airmass across the Mesoscale Discussion area is weakly unstable per 18Z RAP Mesoanalysis (MLCAPE generally 500-1250 J/kg), and is forecast to remain so through the remainder of the afternoon owing to modest 700-500 mb lapse rates (around 6.0-6.5 C/km). Still, steepening low-level lapse rates with diurnal heating and generally 25-30 kt mid-level flow may promote some strong to damaging winds with the more robust updrafts. This localized damaging wind threat may be somewhat greater in association with the eastward moving cluster of thunderstorms approaching southern IL/western KY. In addition to the isolated wind threat, there may be a marginal hail threat with any thunderstorm that can remain mostly discrete along the pre-frontal trough, as weak effective bulk shear is forecast to remain somewhat supportive of updraft organization. Overall, the lack of both stronger instability and shear will likely limit the magnitude of the severe threat, and watch issuance is unlikely.

So what do I think?

Cutting through all the weather jargon, I agree that the threat for damaging winds or hail is low.  However, like we've already seen today, the National Weather Service might issue a warning or two with some of the strongest storms.   

In addition, I believe the bigger threat will come in the form of excessive rainfall for parts of the area and flash flooding will be possible as we see multiple rounds of heavy storms developing as we head into this evening.  

Here's a look at the latest run of the HRRR, hi-res computer model...

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I'll be sure to keep you posted through my social pages as the storms arrive.  Stay tuned and have a safe Easter everybody!  

WDRB Meteorologist Jeremy Kappell

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04/15/2017

A Stormy Easter Expected. Strong Storms and Excessive Rain Possible!

The combination of a slow moving cold front, heating and abundant low level moisture will result in multiple rounds of heavy rain and storms for Easter Sunday.

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Some storms could be strong and in some cases the rainfall could be excessive.

Let's time it out with AdvanceTrak...

AT shows a batch of showers developing during the predawn hours on Sunday.

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This activity could linger to around sunrise. 

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A break in the activity is possible during the mid to late morning hours.

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We'll be tracking the development of a line storms into the early afternoon hours.

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This line of potentially strong storms pushes south into our southern counties by late afternoon.

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Following another possible break in activity, another round of heavy storms develops during the evening.

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The rain could linger well into Sunday night.  

What do I think?

While a few strong storms will be possible, wide spread severe weather is not anticipated.  However, any of the storms that get going during the afternoon/evening will be capable of some gusty winds, frequent lightning and very heavy rainfall.  Locally, the rain could be excessive.

So how much rain?  

Rainfall projection

Locally, better than two inches will be possible for some where storms are able to "train" over the same areas.  If this occurs, then flash flooding could become a concern.  

Stay tuned. Have a safe and blessed Easter everyone!

WDRB Meteorologist Jeremy Kappell

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04/10/2017

Front Brings a Scattered Showers and Storms

Following a pair of brilliant 80 degree days, the arrival of a cold front brings us some cooler temps and the return chance for showers and storms over the next 24 hours.

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Let's time it out with AdvanceTrak...

AT shows clouds increasing, but showers remain west of our area this evening.

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A few showers reach our western counties after midnight.

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Showers and a few storms develop by morning for central counties with locally heavy downpours.

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Showers remain scattered through noon.

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Thunderstorms redevelop with heating across our Kentucky counties tomorrow afternoon.

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Showers exit from north to south tomorrow evening.

How much rain?

Because of the scattered nature to the storms, there's probably going to be a good range in rainfall amounts with this system across our area with most areas receiving between a quarter and three-quarters of an inch of beneficial rains.

Dma rainfall

Fortunately, the severe threat will be low and sunshine is expected to return promptly on Wednesday!

WDRB Meteorologist Jeremy Kappell

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