1/20 - 2:45pm - Bitter Cold Air is Arriving Soon!

Temperatures in the 30's were common last night in West Tennessee and North Mississippi but temperatures are poised to drop much further than that tonight. A dry and relatively marginal cold front is moving through West Tennessee right now and that cold front is the first of two cold shots for the region. This will put lows down into the mid 20's in West Tennessee and lower to mid 30's in North Mississippi as cold air pours in behind the front. This cold air won't allow temperatures to rise much during the day tomorrow either, with highs in the upper 30's closer to Jackson, TN and closer to 50 down toward the Golden Triangle in Mississippi.

During the day tomorrow the second of two shots of cold air will pour in as another cold front passes by. This one will bring the über cold weather that we'll see on Monday night and Tuesday morning. The winds behind this front will be out of the north, meaning the source region (AKA where the air is coming from) for the cold air we'll see during this time will be in the Upper Midwest where they'll be below zero. While that kind of cold isn't expected, mid to upper teens will be common in West Tennessee with readings closer to 20 or 25 degrees down toward North Mississippi. A low of 16 or 17 degrees in Jackson, TN on Tuesday morning looks pretty reasonable given the intensity of the cold air spilling down. While our neighbors to the north may scoff at this being branded as "bitterly cold" in the South, this is still some incredibly cold air. Pets will certainly need to be inside during this time and people need to be bundled up as much as possible. Limit your time outside on Tuesday morning, if possible, and be sure to cover any exposed skin if you do have to be out. Temperatures during the day on Tuesday will warm to a more reasonable lower 30's in West Tennessee and lower 40's in North Mississippi.

Temperatures will moderate during the week thanks to the return of wind flow from the south. This return flow means more moisture in the air across the region. You might guess that this warmer air and more moisture will eventually lead to rain chances... and you'd be right! A low pressure system and associated upper-level shortwave disturbance will track through near the end of the week, bringing rain chances. There's some disagreement between various models over whether this will start on Thursday or Friday. The GFS model's timeline on this is posted below. My guess at this point is that the timeline you see below will be delayed by about 12 hours, so expect rain chances to creep into the region ahead of this low on Thursday afternoon and continue through the night into Friday.

It's not out of the realm of possibility that a little bit of wintry precipitation may fall on the backside of this system on Friday. If cold air flows in behind a cold front associated with this system fast enough then some of the last few rain showers could mix with or change over to a brief period of snow. The GFS identifies Kentuckiana as being the prime target for this but we all know that model has been trending too warm lately in all the winter weather events we've dealt with. So in my mind, West Tennessee is in a potential area for this mix or snow switchover to occur. We're too early for specifics on this so the forecast will have to be fine-tuned during the week. Stay warm!

12/30 - 8pm - Anyone Up for a Third Round of Wintry Weather?

With two winter weather events within a week's time in the books for Kentuckiana, it's apparently time for a third! Unfortunately the timing for this one is pretty bad. Just as folks are going home from New Year's parties in the early hours of Tuesday morning we could have snow, sleet, or even freezing rain falling in the region. The good news here is that regardless of what falls from the sky, there won't be much of it. Precipitation amounts will remain light since heavy rain and storms in the South will be stealing our moisture here up north in Kentucky and Indiana during the time of the event. As far as timing goes, a few snow showers will move through tomorrow afternoon as this system begins to move toward us. Going into the evening is when things get tricky.

As a weak area of low pressure continues to approach we'll see some warming aloft out ahead of it. This warming has the potential to turn our falling snow into sleet or even freezing rain. The GFS is leading the charge at the moment on the potential for freezing rain in Louisville as it has a layer above freezing from 4,000 to 7,000 feet at 4am on Tuesday morning that would support freezing rain. The NAM model keeps us all snow with the entire atmosphere being below freezing. Given that the models have overestimated temperatures aloft with the past two snowstorms we've seen lately, I'm inclined to think that Louisville will stay mostly or all snow. Another thing to focus on will be surface temperatures. Should they be just below freezing this snow, sleet, or freezing rain will stick to the roads and make for tricky travel on late Monday night. If they're just above freezing then only expect to see accumulation on the grass and elevated surfaces. We do have a bit of snowcover in Louisville now, so that might lean us more in the direction of below freezing instead of above for this event overnight Monday into Tuesday. We're going to be awfully close to freezing for much of the night regardless. Areas north of the city will likely stay all snow and below freezing while those areas to the south will see a wintry mix and temperatures just above freezing until the early morning hours. National Weather Service offices across the Plains have issued Winter Weather Advisories due to this system, in purple on the image to the left, but uncertainty about precipitation type and amounts in the Ohio Valley has NWS Louisville waiting for more agreement before they issue any advisories.

Like I said before, accumulations are going to be light for this event. The NAM (right) has up to an inch of snow in many areas and the GFS model has been a little more optimistic at times today with 1-3" across the area. Like the last two snow events, I'm thinking that the amount of precipitation being put out on the models will adjust upward a bit as we get closer to time (tonight and tomorrow morning). Given the trends I'm seeing right now I think we'll see 1-2" of snow in portions of Louisville and points northward with up to an inch of snow and mixed precipitation to the south. Once again... grumble grumble grumble... Louisville is right on the line between feast and famine with the snow. Southern Indiana has been the big winner with snow over the past week while folks south of the Ohio River are raising their hands in favor of more. That is, if you're a snow lover of course. So, we'll be looking to see over the next few hours how the models handle the amount of precipitation forecast, and temperatures both aloft and at the surface. Shifts in these could mean some significant changes to the forecast for many areas!

12/28 - 1:30am EST - Kentuckiana Winter Storm Number 2

Wednesday's winter storm didn't give much snow to folks in the Louisville area and instead confined heavy snow to areas of Southern Indiana. While differences in the models did exist over whether Louisville would get any accumulating snow or not, the overall situation was handled pretty well from a forecast standpoint. The highest snow report in NWS Louisville's coverage area was 7.2 inches in Washington County, IN while Louisville received a trace to a half inch.

The next storm on the heels of the last one is less than 24 hours away as a system arrives from the southwest and stays to our southeast as it moves through the region. This will start as some rain for the Louisville area but as colder air filters in we'll switch over to snow during the later evening hours. This exact time for switchover depends on how warm we get during the day tomorrow (lower 40's versus upper 30's makes a difference!) and how fast the cold air comes in. The 0z NAM that came in earlier tonight has about 3" for the city and after comparing this with other models I'm thinking this may be a number we'll see most commonly reported by Saturday morning in Louisville. Higher totals will be possible just a bit further north from Louisville.

But even as I say this there's a small fly in the ointment. The 3z RPM model is in and it has the possibility of 4-6" of snow just due east of the city and a few very small totals like this scattered throughout areas near the Ohio River. This suggests that totals closer to 4" might be more widespread than previously thought. You can click the RPM output on the left for a larger view. We've seen the trend of increasing snow totals today on the models and this run of the RPM just continues this. We'll need to watch for this trend tomorrow morning to see if other models catch on. Right now this isn't really a factor in my forecast since it's just one model. Below is my snow forecast map for the region. Realize that, like the last storm, a small shift in track or more/less cold air will change things for some folks drastically.

Also worth noting is that the Hyrdrometeorological Prediction Center (HPC) has us in a Slight Risk of a 4" snowfall (think of this like the Slight, Moderate, and High severe weather risks) while areas closer to Cincinnati are in a Moderate Risk. Expect to see Winter Weather Advisories being issued tomorrow for portions of Kentuckiana. There may also be a few Winter Storm Watches issued as well depending on if forecast amounts of 4" or more look to be more widespread. You can keep up with the latest on this storm tomorrow by following me on Twitter and Facebook. Good luck, snow lovers!

12/21 - 2pm - I'm Dreaming of a White (Day After) Christmas

How about that snow last night around Kentuckiana? Most places saw a dusting but areas in Southern Indiana near Orange County picked up about 3 inches since a snow band set up there for a few hours during the overnight. Here at my house in Southeast Louisville we picked up a dusting of snow that blew around a bit in the wind. Temperatures today aren't going to make it out of the mid 30's in Louisville today thanks to the cold air behind the front that passed through yesterday. Seems appropriate given that it's the first day of winter!

Temperatures will moderate for the weekend with southerly flow returning but an area of low pressure moving through will bring rain and even warmer temperatures for Christmas Eve. Booooo! Luckily Christmas Day isn't looking like a washout with just a few clouds and highs in the lower 40's. That's a different story further South in Mississippi, Alabama, and Georgia where rain will be setting up.

Now... onto the fun part. Over the past couple of days the forecast models have been jumping onto the idea of an area of low pressure moving from the Gulf states to the western side of the Appalachian Mountains the day after Christmas. This is concerning because this track favors a snow event for Kentuckiana and even some of West Tennessee. You need to be on the north and west side of these low pressure systems if you want to see some snow since that's where the cold air is confined to. The past few systems we've been on the south and east sides of the lows moving though so that has meant thunderstorms and warm weather lately.

The latest 3 runs of the GFS for this particular post-Christmas storm have been fairly consistent with the low track, which is good! The problem has been that there's been trouble determining how much cold air there will be to work with and how strong/large the low moving through will be. These issues have affected how much snow the Louisville area gets. The graphic on the left is a comparison of the last 3 runs of the GFS for December 26th. For entertainment purposes only, the 0z run had just shy of 8" of snow for Louisville, the 6z had about 3", and the 12z had around 2.5". It is still way, way too far out for specific totals and to worry about the cold air issues yet since things will change likely on the models between now and then. I will say though that the 6 and 12z runs seemed to have difficulty keeping the low as a single, compact system once it matured and instead wanted to go with an elongated large low that tries to interact with another low that develops east of the Appalachians. I've seen this kind of thing happen on the GFS earlier this year with the Nor'easters that we had. Eventually, based on what happened with these Nor'easters, these elongated lows should give way to more concentrated, compact lows on the GFS as we get closer to the actual event. This should help to clear up some of the murkiness with the cold air issues too.

The Euro has been fairly consistent with the track of the low as the GFS has been, but has also experienced a few issues of its own like the GFS. Yesterday's 12z run of the Euro had a blockbuster snow event in the Louisville area while the 0z last night backed off on that prospect thanks to, you guessed it, a more elongated low and trouble with cold air. I can't post the precipitation output from the Euro model since it's behind a paywall and copyrighted, but I can at least show you what the 0z run did with the low after it moved through. Lots and lots of cold air will be behind this system if you couldn't tell by the deep blues and purples on the map!

UPDATE 2:20pm - Today's 12z Euro model run is in and it has a blockbuster storm track for snow for us here in Kentuckiana and West Tennessee. That is quite a strong low in East Tennessee on the left-hand map compared to previous runs. Sheesh.

The CMC and the JMA, which are the Canadian and Japanese models, aren't worth showing here right now. The CMC has the storm running off the east coast and the JMA has a nice low track for some snow in Louisville. It's worth noting that this system might disappear all together on the models or make a radical change. It's still too far out for much certainty.

Also, West Tennessee may see snow from this storm should it take the track that we're seeing. It wouldn't be much snow but certainly more than an inch or so isn't out of the realm of possibility, especially in Northwest Tennessee. Once we get closer to time this will become a bit more clear.

The NAO, which is the North Atlantic Oscillation, frankly isn't agreeing that there will be support for this storm. A negative NAO means blocking near Greenland allows for cold air to flow into the Eastern US and stay locked in place. The current forecast is for a positive NAO during this time, but it has been flipping between negative and positive over the past couple of days. This storm doesn't have to have a negative NAO to happen, but it would help to have it for cold air support and for a storm track that rolls up to the northeast. This will, like the aforementioned models, sort itself out over the next few days.

 

Finally, NWS Louisville has been on board with this storm since yesterday. They're being cautious like they should be but mentioning at length the potential for this at 5 days out is something that they don't do very often. Here's their latest statement:

A much more significant weather system will arrive on the 26th. Both the 00z GFS/ECM and ensembles track a strong low pressure system just to the west of the Appalachian spine which may set us up for our first significant snow. If the low pressure system takes its current forecast track, precipitation would enter the area Wed morning with the bulk of precip occurring Wed during the day and then exiting late Wed night or Thurs morning.

Although there is still much uncertainty in the track of this weather system 6 days out, the possibility is there for significant snow based on the low track and anticipated thermal profiles. BUFKIT GFS showed 8 inches at SDF with a little more than 0.5 inch of qpf. The soundings denote a classic heavy snow sounding with subzero and deep isothermal layer super saturated. The synoptic features of interest are a 110 kt jet max entering a the base of a deepening trough.

For now will have 60% pops on the 26th with rain in the morning and then snow in the afternoon and Wed night. Bing Crosby`s I`m dreaming of a White Christmas may happen, just 24 hours later.

Stay tuned for upcoming forecast updates as this weather system may put a kink in holiday travel plans.

 

This will be a fun system to watch over the weekend. Hopefully there's some snow in our future!

 

12/11 - 10:30pm - Be Careful When Wishing for Snow... You Might Get it!

With all the warmth much of the eastern portion of the nation has been experiencing lately some folks are beginning to get antsy over whether we'll be able to fall into a more winter-like pattern in time for the holidays. The cold front that rolled through earlier this week has helped to assuage some of those fears as it brought much cooler temperatures and even some light snow/sleet to parts of Kentucky and Indiana.

So... What's next? First up is a system that will move through the region this weekend as a warm one. A low will travel from the Plains to Lake Michigan and keep the eastern half of the nation warm as it spreads rain from the Great Lakes to the South. This makes sense because the North Atlantic Oscillation (NAO) will be going neutral during this time, which generally means that cold air won't be able to spill down into the Eastern US from Canada. The Arctic Oscillation will be negative to support cold air coming out of the north, but that doesn't matter too much for us when the NAO isn't negative as well.

The system behind this weekend's is the one that is drawing some concern. A low will be moving across the South during the day on Tuesday and potentially spread some snow to areas that are north of it. At this point anywhere from West Tennessee to the Louisville area is in a potential corridor for snow. This all depends on the exact track of the low and how much cold air it will be able to bring down from the north. This scenario is supported by the NAO and AO both going negative during this time. The GFS model takes the storm along the southern border of Tennessee right to the Carolinas. The ECMWF (European) model starts out with the low a little further south along the Mississippi River but has it exit off the coast in about the same location as the GFS. The low would then become a storm that would ride up to the Northeast just off the coast. With the previous system pulling up toward the Chicago area, this low will likely stay suppressed to the south. So... the broad, general nature of this low's track isn't in too much question. My preliminary (read: subject to change!) thinking is that this will be a rain to light snow situation for portions of Tennessee and Kentucky since cold air would plunge in as the system is exiting to the east. Accumulations would be very light to none.

But here's an issue. The snow cover over the Northern Plains and Upper Midwest has expanded tremendously over the past week as a storm pummeled those areas with quite a bit of snow. We're now at 31.4% snow cover over the United States. Air moving from the north over that snow won't warm as quickly as it would over bare land and the computer models generally have a difficult time resolving that. With this snow cover, the air in place over us and the air coming down from the north may be a little cooler than the computer models think it will be at the moment. That could mean more snow from this system. We're still a week away from this event so while details are sketchy, it's now obvious that this is a system to watch. This likely won't be the only storm we'll have to contend with between now and the new year since a pattern is setting up that will allow cold air to sit close by to the Ohio and Tennessee Valleys while lows track through and just to the south of the region. There's hope for a white Christmas in the region but it will depend on whether we can get enough cold air and a storm to move through just before the 25th. It'll be fun to watch!

6/22 - 10:30am - Storm Chasing: Part 2

Tomorrow morning I leave Louisville for Denver as I set out for one last week of chasing storms with Storm Chasing Adventure Tours this year. This will be a late-season chase, meaning that the threat for severe weather will be much further north than where it was during the peak of the season in May. Unfortunately it looks like the pattern will be a little dull until the middle part of next week due to a ridge of high pressure that will be in place over the middle part of the country. By Wednesday an upper-level low will finally move across Alberta and Saskatchewan, which will bring southwesterly wind flow and maybe even a secondary short-wave disturbance through the Dakotas, Wyoming, and even parts of Nebraska. Moisture looks a bit modest at this point, but it's way too far out to judge that properly since model accuracy is low this many days out.

During the chase next week I'll be posting daily blog updates here and real-time chase updates on my Twitter and Facebook accounts. Each morning I should be able to post a weather briefing as I did back in May so that you'll have the latest on where we'll be headed to and why. Hopefully we'll be able to find some good storms!

6/19 - 3:15pm - The Last Day of Spring

Tomorrow marks the first day of summer as the summer solstice occurs at 7:09pm EDT. The summer solstice put simply is the longest day of the year in the northern hemisphere because the north pole is tilted toward the sun. The sun will be directly overhead at 23.5 degrees north latitude or the Tropic of Cancer, located on a line that runs between Cuba and Florida. Meteorological summer, the three month period that meteorologists consider summertime in weather terms, started on June 1st with hurricane season.

I'll tell you that it's been pretty warm in Europe over the last couple of weeks. My family and I enjoyed a very nice trip around the Mediterranean Sea and traveled to Italy, Croatia, Turkey, Monaco, and Spain. I'm still a little jet-lagged from the marathon flight between Barcelona and Philadelphia we were on Sunday, but I'm slowly acclimating to Eastern Time again. Crazily enough, a tornado touched down in Venice, Italy last week well after we had left port on our ship. Thankfully there were no injuries, but some damage was done in a place that rarely sees tornadoes. Read more about what happened here.

The heat we had in Europe followed me home to Louisville (not meteorologically of course) and now we're experiencing quite a heat wave. High temperatures are expected to be at or above 90 degrees for most of the week here, but we may get a small break on Thursday night/Friday morning thanks to a cold front approaching the area. This thing may run out of steam just as it's nearing the Ohio River late on Thursday so rainfall chances could be slim with this.

If it continues to chug along further south than expcted we could have some storms around during this timeframe. Areas in Western Kentucky and Northwest Tennessee do need the rain, but unfortunately this won't be enough (if it happens at all) to assuage much of the drought in that region. The US Drought Monitor from the University of Nebraska-Lincoln has portions of this area under a moderate to severe drought. 

In just four days I'll be heading to Denver to join Storm Chasing Adventure Tours for one more week of storm chasing this year. It's been a whirlwind of a summer break for me so far with three weeks of storm chasing and two weeks of travel in Europe under my belt, but I'm definitely excited for another week of chasing! It looks like storms may fire up early to mid next week in the Dakotas, Nebraska, and Wyoming as an upper-level disturbance inches onshore from the Pacific. It's a bit far out for specifics at this point, but I think moisture and upper-level support during this time might be decent if this disturbance comes onshore in time. The limiting factor may be capping (warm air) aloft since temperatures may be a little high up there. It'll be interesting to see how this develops over the course of the week!

Be sure to follow me on Twitter and Facebook so that you'll be ready to receive my instant storm chasing updates next week!

 

5/18 - 2:45pm CDT - Regarding Next Week's Chase

As we make our way back to Oklahoma City on our last day of this week's storm chasing tour, I'm looking over quite a bit of data for next week's severe weather potential. After a lengthy period of high pressure ridging across the Plains (A.K.A. no storms) we're finally seeing signs that a large-scale trough will begin to move onshore from the Pacific and begin to affect the Plains during the middle part of the week. A smaller trough will be coming through this weekend as well but not a lot of moisture and our inability to chase during its peak on Saturday due to our down day in Oklahoma City means it will not be discussed here.

This trough coming in next week will need some moisture to work with for severe weather to form. This is something we've had a problem with for a while now but it looks like the Gulf of Mexico will finally be "open for business" starting next week. As the trough begins creating southwesterly winds and diffluence aloft in Kansas extending into Northwest Oklahoma on Wednesday (5/23), southerly winds at the surface should begin to bring in some much-needed moisture. The degree to which this will happen is still very much up in the air at this point because the GFS model has been consistently overshooting actual dew points, meaning it's been too optimistic about moisture return. The European model does agree that moisture will begin flowing into the Plains on Wednesday, but to a lesser degree than the GFS on the right.

This setup will continue right into Thursday and Friday as the trough digs in and moisture continues to flow into the region. These two days may harbor better severe weather chances than Wednesday due to having more time for moisture to return. Given the possibility that small-scale weather phenomena like cloud shields and overnight storms could limit potential on any of these days it's very difficult to point out which of them will be the best for storm chasing. Not only that, but the aforementioned computer model issues and amount of time between now and the trough moving into the Plains creates an even bigger margin of error. It's safe to say right now that things are certainly looking more favorable synoptically (on a large scale) for severe storms, but calling for a tornado "outbreak" at this point wouldn't be logical due to the variability of all the smaller features involved. This setup certainly has our attention and we're keeping close watch! Our robotic streaming webcam has been sitting dormant since we haven't had any storms lately, but we're hoping that we can put it in action next week.

Follow my storm chasing updates on Twitter and Facebook!

5/17 - 4:15pm MDT - Some Fun in Denver!

Since good storms for chasing didn't form yesterday and won't form today, we're having a bit of fun in Denver, Colorado! Today we split into a few groups, one group that toured the Front Range of the Rockies, one that went to the Denver Art Museum, and another that went to the Elitch Gardens theme park in town. We all had a great time and will meet up this evening for dinner. Tomorrow we'll be heading back to Oklahoma City as Tour 2 ends and we'll be saying goodbye to our guests on Saturday morning.

For next week's tour, Tour 3, there may be a return of severe weather to the Plains. This may take until midweek though as a large-scale trough moves inland from the Pacific and moisture flows back into the region near the surface from the Gulf of Mexico. A lack of moisture in the Plains has plagued us for days now, so this return will be very welcome if what the long-range GFS model indicates pans out.

Be sure to keep up with my updates on Twitter and Facebook!
 

2/27 - 4:15pm - Two Shots of Severe Weather This Week

This will certainly be an active week across the Southeast as two storm systems cause trouble for many. The first of these severe weather events will affect West Tennessee and North Mississippi on Wednesday and the second should move through on Friday.

Wednesday

At this point it looks like we'll be tracking storms moving out of Arkansas into West Tennessee and North Mississippi on late Tuesday night after a few showers and possibly a storm pass through during the day on Tuesday. While these storms could have some potency over Central Arkansas, the thinking at this point is that they will weaken overnight as they lose the heating of the day. The best wind shear for these storms will be in the Jackson, TN area as they move through on Wednesday morning into the early afternoon ahead of a cold front, but without much of the needed instability that daytime heating helps to generate the storms shouldn't be too intense. They may very well reach severe limits with some wind and hail, but I think the worst of the storms will be more in Middle Tennessee where they'll have time to re-fire during the heating of the day. The Storm Prediction Center has 30% Slight severe weather risks over Arkansas into extreme West Tennessee on Tuesday and then has the same risk area in Middle Tennessee/extreme Northeast Mississippi on Wednesday. The worst severe weather will effectively leapfrog most of West Tennessee according to these two outlooks, and that looks like a fair forecast right now given the timing of the storms over the region.

Further south in North Mississippi the situation should be about the same, but with a little less wind shear support for severe storms and a later timing for them to move through (later Wednesday afternoon) since the cold front will stall near the MS/TN border for a while during the day (see left image from the 12 NAM). The NAM and GFS models agree that North Mississippi will have higher dew points (more moisture) than West Tennessee, but without great wind support this shouldn't lead to a noticeable increase in storm severity. I should point out that both locations could see a possible isolated tornado or two, but this should be a very low chance given the lack of good low-level wind shear.

Friday

Friday's severe weather event is not a clean-cut as Wednesday's is at this point, but it's looking more and more like this one will feature more intense storms. Another cold front passing through on Friday night will provide a focus for what could be a couple lines or clusters of storms. Right now the GFS and European computer models agree that this will likely not be a tornado outbreak because of the lack of low-level shear much like Wednesday's event, but the two models can't agree on how much moisture makes it northward from the Gulf. The GFS has 65 degree + dew points making it all the way into West Tennessee on Friday whereas the European is not as optimistic. This also plays into who sees the best instability too, so it's not clear right now as to who will see the most severe storms on Friday. It is safe to say that West Tennessee and North Mississippi may have to deal with high winds and maybe even some hail on Friday, and it will likely be more intense than Wednesday based on current data.

Southeast Severe Storms Symposium

To those who are attending the 10th Annual Southeast Severe Storms Symposium at Mississippi State University on Friday and Saturday, we will go on as planned even if there is severe weather in the region. While many meteorologists who will be presenting may not be able to attend because of the risk for severe weather in their respective coverage areas, we should be able to have most of them present their sessions to the symposium via Skype. I'm leading a group of meteorology students who will be live tweeting the symposium on the official Southeast Severe Storms Symposium Twitter account @SESSS12. Be sure to follow us!

2/11 - 5pm - A Wintry West Tennessee Forecast

A front that passed through West Tennessee last night brought rain showers during the overnight hours and snow showers this morning across the region. These have since moved out of the area, but the snow came down in some heavy bursts at times even though there was really no accumulation. High pressure will provide the setup for a very cold couple of days with highs in the 30's and overnight lows in the teens. Yikes! Tonight could be the coldest night of 2012 so far, which really isn't saying much since we've been pretty mild as of late.

Monday's forecast is flat-out complicated. Warm air overriding the retreating arctic air mass in place from this weekend will set the stage for a storm that could put down snow, sleet, and even freezing rain. Most indications are that this will start off as snow across most of West Tennessee on Monday afternoon as the lower layers of the atmosphere moisten up, but this snow could switch over to a period of wintry mix later on in the evening as the atmosphere warms up more (notice the warm "push" at 850 mb - 5000 ft on the left). Once we reach a certain threshold of warming on Monday night into the wee hours of Tuesday morning, all the snow, sleet, and freezing rain should transition to plain rain and the wintry weather headaches will be no more. Before everything switches over to rain an inch or so of snow could be on the ground around the I-40 corridor, including Jackson, according to the latest forecast models. Areas in Northwest Tennessee will switchover to rain a little later on than I-40, so there may be up to two inches on the ground. This is nowhere near set in stone yet and I'm willing to bet we'll see a few small changes in this forecast before the weekend is over.

The models agree that snow will fall across West Tennessee on Monday, but there are differences in when exactly this warm layer aloft will come in enough to switch the snow and wintry mix over to rain. The 18z NAM seems the most conservative on snow amounts at this point, with only a half inch in Jackson on Monday night. It also suggests that we might avoid a wintry mix and switch immediately over to rain. There's even a brief shot of rain just before the snow starts on that model. The GFS is bullish on snow amounts with over an inch in Jackson with the aforementioned wintry mix period (depicted as freezing rain on the BUFKIT output to the right) before the switchover to rain. The main issues seem are the timing of the warm air intrusion aloft and how strong it will be. So while this won't be a huge winter weather event by any stretch of the imagination, a few travel issues may crop up on Monday evening as the snow and wintry mix is falling.

Check out the video below from this morning's newscast on WBBJ for more details on your forecast!

1/17 - 5:15pm CST - A Day of Tornadoes in Kentuckiana and Mississippi

Two tornadoes have now been confirmed by NWS Louisville in Kentucky and Indiana. The first of these is an EF-1 that caused damage in the Springhurst area of Northeast Louisville (photos from John Belski's Weather Blog):

...EF-1 Tornado Confirmed in Jefferson County Kentucky...

Brownsboro Rd, Louisville

Damage Type: Tornado
Date: Jan 17 2012
EF Scale: 1
Wind Speed: 95 MPH
Path Length: 4.2 MILES
Path Width: 250 YARDS

Narrative: An NWS storm survey has confirmed an EF-1 tornado in Jefferson County, Kentucky.  The tornado touched down near the intersection of I-264 and Brownsboro Road.  The tornado tracked northeast to near the intersection of Hurstbourne and Brownsboro Road where it briefly lifted.  The tornado then reformed and crossed I-265.  The preliminary path length is 4.2 miles with a path width of 250 yards. This storm survey is ongoing and information in this statement will be updated as it becomes available.

The second tornado hit the airport in Madison, Indiana and carries an EF-0 rating with 85 mph winds:

...EF-0 Tornado Confirmed in Jefferson County Indiana...

Madison, IN Airport

Damage Type: Tornado
Date: Jan 17 2012
Start Time: 10:40 AM EST
End Time: 10:40 AM EST
EF Scale: 0
Wind Speed: 85 MPH
Path Length: 0.3 Miles
Path Width: 60 Yards

Narrative: An EF-0 tornado touched down at the Madison Municipal County Airport. Damage was confined to IMS Lane. The tornado touched down briefly along this path and moved an at least 500 pound dumpster 35 feet southeast. It also moved a Beechcraft/King Air plane 10 degrees and the nose gear was broken. The airport operations building had a disabled awning and post. Part of a hangar`s siding came off with siding and insulation up in trees. Several trees were snapped along the narrow path. A witness saw the swirl as the tornado touched down.

It's worth noting that the Storm Prediction Center did not issue a Tornado Watch today during this severe weather event. There may be more tornadoes confirmed in the Louisville area tomorrow as more surveys are conducted, especially in Clarksville, IN where damage has been well publicized. Two tornadoes were also reported in Mississippi this afternoon in Tippah and Marion Counties:

1800		3 NE DUMAS	TIPPAH	MS	3467	8880	TORNADO SIGHTED IN THE DUMAS PINE GROVE AREA NEAR HIGHWAY 4. (MEG)
2207		7 E SANDY HOOK	MARION	MS	3104	8969	PROBABLE TORNADO ... MOBILE HOME DESTROYED WITH PERSON POSSIBLY TRAPPED ... NUMEROUS TREES AND POWER LINES DOWN ... EMERGENCY PERSONNEL HAVING DIFFICULT TIME REACHING THE SIT (JAN)

Ratings on these possible tornadoes will likely come tomorrow when NWS crews are able to get out and survey the damage.

Unfortunately severe weather could become an issue again this time next week as a potent trough moves through the Southeastern portion of the nation. The GFS and Euro computer models indicate ample upper-level support and moisture return for a severe weather setup, but this is not set in stone yet as things can change in a week's time. Stay tuned!

12/26 - 12:30pm - Post-Christmas Snow Chance?

While many did not have a white Christmas yesterday, it certainly was a nice day across much of the East US with warm temperatures. We now turn our attention to a system that will be bringing much of the Southeast rain and possibly some snow as you head northward. This system is brewing in the Gulf Coast states right now and will bring West Tennessee rain this afternoon through tomorrow and the Louisville area rain tonight through tomorrow. While West Tennessee will likely stay all rain throughout the duration of this system due to warmer temperatures, Kentuckiana may have to deal with some snowfall during the afternoon tomorrow. The track of this storm from Tennessee to Eastern Kentucky is usually one that gives us our bigger snow events during the winter, but this time that won't be the case because of the lack of cold air we'll have to work with.

The forecast for snow is a tough one because we'll be dealing with colder air coming in on the backside of this system to give us our snow. This means that the atmosphere will cool from top to bottom and while snow will be falling it will likely not accumulate much, if any, because the air at the surface will still be warm while the upper atmosphere cools down. Nevertheless, a switchover to snow in the Louisville area will likely happen sometime tomorrow during the early to mid afternoon hours as cold air penetrates enough of the atmosphere to keep snow falling all the way to the surface. The NAM (left) seems to be the most aggressive on this switchover right now due to the surge of cold air it brings in early on in the afternoon in Louisville but the forecast sounding, or a vertical snapshot of the atmosphere at a given time, still indicates that we'll have temperatures just above freezing near the surface. This means that snow will be making it to the ground, but will likely melt on contact or accumulate lightly on the grass and elevated areas in heavier snow bands. Speaking of banding, that's another issue we could face. Snow banding is when you get a thin strips of heavy snow falling that look like bands due to winds coming together in these areas. These bands can produce snow accumulations even when temperatures are above freezing, just like in Jackson, Tennessee earlier this month when over an inch of snow accumulated with temperatures just above freezing.

Overall, I think areas in and close to Louisville can expect a dusting and maybe up to an inch of snow on grassy and elevated surfaces at some point tomorrow evening. If cooler air does not come in as quickly as expected this will remain a rain/snow mix or even just plain rain. Areas north and west of the Ohio River have the best shot for a light accumulating snow as they'll be slightly cooler and have an earlier switchover during the late morning hours. Most of the models are agreeing that we'll stay above freezing during most of this event, but we will be dipping down below that mark late Tuesday evening. This may create slick spots if any roads are wet from the snowfall during the afternoon. The 12z NAM (top left) is indeed the most aggressive on snowfall totals around here by looking at the snowfall output map, which you can see a larger view of by clicking. The 0z GFS (bottom left) is less aggressive, which is typical for it lately, and the Euro (which I cannot post here to copyright policies) keeps the snowfall along and north of the Ohio River. There are still a lot of small variables like exactly how fast the precipitation will move out of here and how much cold air will actually work into this process, so little details like these can drastically alter who gets snow and how much.