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55 posts from December 2016


Active Pattern Resumes to Start 2017!

In line with what we've been seeing a lot of over the last 4 or 5 weeks., 2016 ended on a wet note with 0.07" officially recorded at the Louisville International Airport giving us more than 5 inches since December 1st bringing an end to the drought that had plagued the region over the past couple months.


Now we turn our attention to a pair of storms that promised to bring MORE rain to start the new year with the first one arriving late tomorrow and the second one into Monday night.


Let's time it out with AdvanceTrak...






AT holds off the rain until late afternoon/evening on New Years Day with only light stuff expected.  The gloomy conditions look to stick around all day.

The stronger of the two systems arrives Monday and into Monday night. 


While showers will be possible during the day on Monday, the best chance for rain looks to hold off until evening with a line of thunderstorms possible!


While the severe threat remains low, there will be the possibility of locally heavy rain! 

WDRB Meteorologist Jeremy Kappell

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Ending 2016 on a Damp Note

Showers are moving into the region from south to north and they will be widespread during the morning and early afternoon. However, they will not be clearing out completely for the evening. Most of the precipitation today will be rain, although earlier this morning there was a brief mix of snow and sleet and there could be a few times tonight this happens again. The bulk of the rain will be ahead of a cold front, which is just out to our west, however we still have a chance for a few pesky showers later tonight. 

12-31 surf map

Before we time out the rain, one thing to note, it has been gusty for a few days and today will be no exception. We will see winds around 20-25 mph and gusts up to 30-35 mph. This will make a damp and cold day, feel even colder and more miserable. Our highs will be in the mid 40s, but it will feel significantly cooler. 

12-31 wind speeds

Showers will be widespread by this afternoon, from the top to bottom of our viewing area. It will be all rain and generally light, besides a pocket here or there of moderate rain. 

12-31 AT 1 pm

By this evening, showers will become more scattered and begin to taper off. However, they will not completely clear the region. My suggestion for this evening is to keep the umbrella handy! 

12-31 AT 5 pm

Notice by 9 pm, there are still a few pesky showers. I do think the best chance for these showers will be for our southern counties, however, I cannot completely rule out an isolated shower for metro or southern IN. 

12-31 AT 9 pm

And when it is time to ring in the new year?

The coverage of showers is significantly less than this morning and afternoon, however you may still have to dodge a shower or two. Notice Advancetrak still has a shower in our north, metro and southern counties. They are spotty and light but they are there. I don't think they will have a huge impact on your night, but if your goal is to stay dry, be aware there is still a 30% chance for rain for the beginning of 2017!

12-31 AT 12 am

And although today's rain will be a bit pesky, we shouldn't expect much in terms of rainfall totals. Roughly a tenth to a third of an inch is what we can expect. 

12-31 rainfall totals

Here is the probability of precipitation for metro this evening along with the temperatures. It will be cold and breezy too! Dress warm! 

12-31 nye planner

The first week of 2017 is going to be an ACTIVE one. Potentially strong to severe storms to start the week with temps in the 60s and snow showers with teens to end it. Jeremy will riddle it all out for you this evening on WDRB News! 

I hope you have a very safe evening if you are going to be out and about! The rain could make the roads slick. Plan ahead and go slow! :) 

Happy New Year and I'll see you in 2017! 

-Katie McGraw 

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Do you want to build a snowflake?!

Q: How are snowflakes formed? 

A:  A snowflake begins to form when an extremely cold water droplet freezes onto a pollen or dust particle in the sky. This creates an ice crystal. As the ice crystal falls to the ground, water vapor freezes onto the primary crystal, building new crystals – the six arms of the snowflake.

That’s the short answer.

Snow flake formation

The Longer Explanation: 

The ice crystals that make up snowflakes are symmetrical (or patterned) because they reflect the internal order of the crystal’s water molecules as they arrange themselves in predetermined spaces (known as “crystallization”) to form a six-sided snowflake. 

Ultimately, it is the temperature at which a crystal forms — and to a lesser extent the humidity of the air — that determines the basic shape of the ice crystal. Thus, we see long needle-like crystals at 23 degrees F and very flat plate-like crystals at 5 degrees F.  

The intricate shape of a single arm of the snowflake is determined by the atmospheric conditions experienced by entire ice crystal as it falls. A crystal might begin to grow arms in one manner, and then minutes or even seconds later, slight changes in the surrounding temperature or humidity causes the crystal to grow in another way. Although the six-sided shape is always maintained, the ice crystal (and its six arms) may branch off in new directions. Because each arm experiences the same atmospheric conditions, the arms look identical. 

Q: So, why are no two snowflakes exactly alike? 

A: Well, that’s because individual snowflakes all follow slightly different paths from the sky to the ground —and thus encounter slightly different atmospheric conditions along the way. Therefore, they all tend to look unique, resembling everything from prisms and needles to the familiar lacy pattern.  

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-Katie McGraw 



New Year Brings Same Up & Down Wild Weather

From Jude Redfield...

     Sunrise on Saturday might have a glimpse of sunshine (briefly) before the gloom show begins. Light rain, *possibly* mixed with wet snow breaks out between 9am and noon. Air temps will be in the mid to upper 30s so don't expect problems on the roads even if the snow would happen to mix in. This is a weak system that produces scattered light rain on and off tomorrow. If the rain doesn't develop as predicted then air temps could make the mid-upper 40s due to such a strong south wind. If we keep the rain on and off as currently projected then it will be difficult to make it out of the low 40s. Either way Saturday ends up cloudy and cool.

    Most of the rain will be winding down by Saturday evening. This leaves us with a small chance for sprinkles, light rain and drizzle from midnight through Sunday morning. Air temps remain above freezing overnight Saturday so we should escape any road hazards.

Please see future radar images below for the estimated timeline.






*If clouds thin in southern and central Indiana overnight Saturday a brief drop to near freezing is possible. If this occurs the roads should be dry in these locations which would allow us to avoid any problems.*


    Sunday's rain chance isn't overwhelming coming in at 40% - 50%. Most of Sunday is completely dry.


    Next week is typical Kentuckiana weather. High temps in the 60s are possible Monday and Tuesday. Locally heavy rain with gusty storms develop late Monday into Tuesday. This is followed up by an arctic cold front. MUCH COLDER air invades late next week.  I am totally confident on this portion of the extended forecast. It become more fuzzy when discussing our snow potential late next week. We will need to watch energy coming out of the southwest. This COULD lead to a snow scenario somewhere in the Ohio and Tennessee Valley Thursday into Friday. Nothing more than something to monitor at this stage of the game.




Snow Squalls Possible: When and Where

A few hours this evening could be a bit hazardous on the roads due to the development of snow squalls that will result in low visibility and almost blizzard-like conditions. However, they will be more localized and for a much shorter period of time than a blizzard. But there could still be white out conditions for those that get caught in some of these intense snow bursts. There could be a coating to about half an inch of accumulation at best, but it could happen rather quickly.


The best chance for these snow showers is going to be from 5-10 pm tonight (Thursday 12-29). 

12-29 at 730

12-29 at 11 pm


Let's be clear, not everyone is going to see snow this evening. These snow bands are going to be similar to scattered storms we see in the summer that develop where the conditions are favorable. They are hard to predict *exactly* where they will develop but we try our best to get the general area right. It appears SE Indiana has the best potential to see this snow and it becomes progressively less likely the further south you go.

12-29 snow burst

It has been a gusty day all day and the windy conditions are going to make visibility an issue if snow squalls happen around your home or where you are traveling this evening. Sustained wind speeds could be up to 20-25 mph and gusts could be even faster. This is what could lead to the white out conditions. 

12-29 winds

Not only will visibility be an issue, but the roads will be slick as well. Take it easy on the roads!

12-29 snow talk

Rick will have update this evening on WDRB about this snow possibility and he is also tracking out another system for the last day of 2016! Be sure to tune in to learn all the details! 

We will be keeping you posted on social media as well. The links to my pages are below: 

Katie McGraw's Facebook Page

Katie McGraw's Twitter Page

-Katie McGraw 



Snow Bursts A Real Concern For Some

From Jude Redfield...

     After a day filled with sun expect clouds to puff up and eventually produce a few snow bursts. These will be brief, but intense snow showers that will be capable of dropping a quick covering where they roam. NOT EVERYONE IS GOING TO SEE THESE SNOW BURSTS.  Central Indiana should see development around 3-4pm. These will race to the southeast into southern Indiana around 5pm.  Please turn your attention to the future radar images below to get an idea of expected coverage and intensity. (radar images below do not show precip type because this color table shows the intensity much better)




    Initially a few of these could be mixed with rain/sleet/snow pellets. Since we will have the dots of bright colors showing up on the radar (pictured above)  it is pretty safe to bet on these isolated squalls causing some hazards.  IF, IF, IF you encounter one of the squalls plan on wind gusts of 30-40 mph and blinding bursts of snow. These wouldn't last more than a few minutes, but could quickly dust up the roads where they occur. I WOULDN'T BE TOTALLY SHOCKED IF A FEW OF THESE PRODUCE A COUPLE LIGHTNING STRIKES IN THE OHIO VALLEY


The most intense bursts will exit to the east after 10pm and become much less numerous.  Scattered flurries and light snow showers are possible through the overnight.


The map above shows where the bursts are most likely and vice versa. Make sure you understand even in locations shaded in blue we don't expect a 100% chance everyone will deal with snow squalls. These are very similar to how pop up showers and storms act in the summer months. Some get hit, some swing and miss. 

    Make sure to follow Katie McGraw and Rick DeLuca this afternoon and evening for a more in depth look at the snow shower potential. They will be able to track them as they pop up across Indiana. -Jude Redfield-


Watercolor Painting or NOAA Satellite Image???


A large dust cloud hangs over the Atlantic along the northwestern coast of Africa in this color-enhanced image captured by the NOAA/NASA Suomi NPP satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on December 27, 2016.

The bright colors shown here are the result of a "dust enhancement" -- an experimental data product created by scientists at the European Organisation for the Exploitation of Meteorological Satellites (aka: EUMETSAT). Based on infrared channel data, this RGB (red-green-blue) enhancement was created to help analysts monitor the evolution of dust storms. According to EUMETSAT, monitoring of dust in the atmosphere 24 hours a day can be a challenge because the appearance of dust in satellite imagery changes drastically from day to night. Incorporating VIIRS day/night band into the mix of channels used to produce these images makes it easier.

So where is the dust visible in this image? Well, it's not represented by the orange/brown color--that's atmospheric moisture. Rather, the dust appears as magenta or pink. The other colors denote the following: Reds mark thick cirrus clouds, dark blues are thin cirrus clouds, and the other shades of blue indicate the surface (land and water) of the Earth. The bright yellow is the hot surface of the Sahara. Compare this RGB image with the true color image found here.

To learn more about the effect of atmospheric dust on the Earth's weather and the various ways scientists use satellite imagery to detect it, click here.
Note: "experimental" data products are those that are still in development.

Image and Information Courtesy NOAA

WDRB Meteorologist Jeremy Kappell

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OUTLOOK: January 2017

A quick update to the blog from last night.  Data continues to support the idea of a prolonged cold wave as we head into January.  Today's runs of both the GFS and Euro support a full scale Arctic Invasion into the Central US by midweek next week.

The EURO EPS or European Ensemble Prediction System temperature anomaly map shows an ENORMOUS area of below normal temps that almost covers the entire US grid by next Thursday.  Locally this would represent temps running about 15°F below normal with highs perhaps not escaping the 20's and lows much colder than that!


With the cold will come snow chances too late next week.  Full discussion below...


As discussed with the release of the 2016-2017 Winter Outlook, I believe the months of January and February remain primed for harsh winter conditions over much of the Central and Eastern United States.  For the purpose of this article, I will focus on only next month. 

While we have seen a nice reprieve from the cold over the last few days, Arctic air remains firmly in place over Siberia, Greenland, Northern Canada and Alaska where temps remain well below zero.  In fact, a jaw dropping low temperature of  -79.6°F was recorded last week over Central Siberia breaking all-time records for the region!

GFS NH Temps

Eventually, this cold will spill over into our side of the hemisphere opening the door for major arctic outbreaks during the month of January.

The real question becomes when?  

While data from both the Euro and GFS agree that January starts off on a mild note with temps running in the 50's and perhaps even 60's early next week.  After that, it appears that we will go into a progressively colder pattern that could last for much of the next month to come.  

Taking a look at a forecast snapshot of jet stream winds from the GFS valid on January 9th reveal several telltale signs of what may be coming our way. 

Gfs jetstream

The first thing to notice are the lobes of high pressure over both Alaska (think EPO here) and also the North Atlantic (NAO).  The locations of these highs, as described in the Winter Outlook, help promote a "cross-polar flow" while trapping the exit of cold air intrusions out of Eastern North America.  Also of note is the presence of that giant low over Southern Canada, you guessed it, that's the Polar Vortex!  

Explaining a couple "teleconnections"...

A "teleconnection" is a connection or correlation between meteorological phenomena that occur a long distance apart and can help to signal changes in climate and weather patterns from region to region.

NAO - North Atlantic Oscillation

One of the most commonly looked at teleconnection patterns for weather forecasting. The value of the NAO is determined by the differences in pressures over the high latitudes and central latitudes of the North Atlantic. The positive phase of the NAO is characterized by a low difference in pressure between the two regions, a below average pressure over the high latitudes, and an above average pressure over the central latitudes. The opposite occurs during the negative phase. The NAO is significant in forecasting because its state affects the intensity and location of the jet stream and storm track in the North Atlantic. As a result, significant changes in temperature and precipitation occur in Europe and North America based on the NAO.


EPO- Eastern Pacific Oscillation

A dipole pattern similar to the NAO in the Atlantic, but located in the eastern Pacific. There is a tendency for heights/pressures/temperatures to be higher to the north and lower to the south in the negative phase and lower to the north and higher to the south in the positive phase. The negative phase corresponds to widespread cooling over central and eastern North America and the positive phase to warming.


The Euro and the GFS agree that both the NAO and the EPO look to go into their negative phase over the next week to ten days leading to a likely outbreak of arctic air into portions of the United States. 

Looking into the Crystal Ball...

While the medium range forecast models such as the GFS and Euro show arctic air arriving into the Northern US in about one week, you have to turn to the long range or "climate" models to get a handle on what to expect over the course of several weeks.  

Here's a look at three snapshots of temperature anomalies via the "Euro Weeklies" climate model during the month of January 2017...

EPS: Valid January 5 - 9


The Euro EPS clearly shows the arrival of a massive amount of Arctic air into much of North America with the heart of it building into the Northern Rockies and  Northern Plains.  Locally, temps fall a few degrees below normal for this time of the year, which by the way is pretty cold. 

The Climate Prediction Center


The folks at CPC wholeheartedly agree with this forecast with the vast majority of the Continental US expected to be below normal temperature wise in the 8 to 14 day range. 

EPS: Valid January 17 - 21


While the Euro EPS shows some modification of the arctic air mass over the Northern Rockies, the cold spreads throughout the Eastern US and remains firmly in place here locally during the middle of the month, which is also our climatological coldest part of the year.

EPS: Valid January 26 - 30


Finally, during the final week of the month the EPS shows temps gradually recovering to near normal in our area and a little above normal for much of the Eastern US.

So what do I think?

As mentioned in the 2016-2017 Winter Outlook, I remain confident that we are looking at a rough January with brutal cold for much of the month.  Keep in mind, that the above mentioned Euro EPS temp anomalies are with respect to "normals" for this time of the year and normal is cold with average highs running in the lower 40's and average lows into the 20's during the month of January.  So a prolonged stretch of below normal temps could mean highs routinely not escaping the 30's and even 20's especially if we get decent snow cover. 

What about snow?

While I remain confident that this will turn out to be a cold January, the prediction of snow is much more complex.  Typically you can't predict snow with much accuracy at all outside of a few days out.  However, with the expectation of plenty of cold this month, it certainly helps our chances.  Now all we need is the moisture. 


According to the Climate Prediction Center (CPC), in addition to the cold, we are looking at above normal precipitation during in the 8 to 14 day range with near normal precip during the remainder of the month. 

With that being said, and all else being equal, I remain bullish on the idea of catching some decent snow this month.  

The devil will be in the details however, so stay tuned!

WDRB Meteorologist Jeremy Kappell

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Trio of Storms to Impact Final Week of December!

It felt a lot like spring today.  The high of 76 degrees, not only establishes a new record for the date, but also ties the warmest temp ever recorded during the month of December previously achieved on December 3, 1982.  

Now, we monitor a trio of storm systems that will be impacting our weather over this final week of the year with the first one arriving in the form of a cold front this evening bringing more good rains and and end to the extreme warmth. 


The second two will make for a complicated forecast as we head into New years Eve and New Years Day. 

The upper low located over the North Pacific looks to deliver a shot of cold for the end of the workweek and into the start of the weekend.  

The storm off the Southern California Coast is then expected to ride in behind it increasing moisture and eventually bringing warmer temps too.  

The latest data from the GFS shows the progression of how New Years Weekend may unfold...


The GFS is currently showing precipitation developing Saturday morning with surface temps in the 30's and subfreezing temps a short distance above us. This would translate to a wintry mix of rain/snow and possibly sleet. 


From there, surface temps gradually warm as the cold air aloft pushes further north leading to a transition from wintry mix to a cold rain for our Kentucky and metro Indiana counties as the mixed bag continues into Central/Northern Indiana.


By Saturday night it's all rain across our area with heavy storms developing to our south into Dixie.


From there, rain comes to an end Sunday morning with temps well above freezing.


At this point it looks mild and mainly dry for New Years Day. 

So what do I think? 

While not a lock for wintry precip at this point, data suggest that the chance is increasing for the first half of the day on Saturday with the best chance for this occurring across Southern Indiana.  By late on New Years Eve precipitation should transition to all rain for the viewing area which is good news for those with travel plans as we ring in the new year.  However, it could be quite wet.  Stay tuned!  

Rick has a full update on WDRB News this evening.

WDRB Meteorologist Jeremy Kappell

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Spring Fling Fires Up Strong Storms

From Jude Redfield...


    Record warmth today as high temps end up in the low-mid 70s. This fuel will help storms develop in southern Indiana this afternoon. They will then begin a move to the south. While the entire line of storms will move slowly to the south the actual individual storm cells will rocket to the northeast at around 50mph. Strong wind energy is present so a few of the stronger storms could produce gusts in excess of 45mph. An isolated severe storm can't be ruled out, but widespread severe storms don't look likely. Rain amounts of a half inch to one inch are likely for a large chunk of Kentuckiana. Isolated higher amounts are possible. Posted below are future radar images indicating the estimated time of arrival.




Make sure to watch Jeremy Kappell between 11:30am and 12:30pm on WDRB News for the latest. Also Rick DeLuca will have live radar updates starting at 4pm on WDRB News as the line of storms approaches. -Jude Redfield-