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01/28/2014

Some data suggests a BIG storm in our region next week! We are assessing the threat to our area...

If winter were to come to an end tomorrow in Louisville, it will have already been a very notable one with multiple bouts of severe cold and several rounds of snow.  However, we still have February too look forward to, which climatologically speaking, is the snowiest month of the year in Louisville.  

Now that we are beginning to focus on mid and long range models that go well into the start of the new month, it is becoming apparent that the start of this February will be an active one.  

We are tracking two systems that will be arriving during the first week of the new month with the first one arriving Saturday and the second one arriving Tuesday and into Wednesday next week.  

You can see these systems below in the upper level jet stream winds over the North Pacific.  (I've placed a small star over Louisville for location reference)

Jet stream NA

Obviously, we have a lot of territory between us and the oncoming systems but already a few things are already becoming clear.  The first system on Saturday looks to be accompanied by too much warm air for much, if any, threat of wintry weather.  At this point you can chalk this one up to just some plain ol' rain for our area and this is where the discussion about Saturday's system will end.  

It is the second one that is already creating quite a bit of buzz on the internet and social media.  There have been several runs of our two primary longrange weather models, the GFS and EURO, that could potentially bring significant accumulations of both ice and snow for portions of our area.  

The latest run of the GFS (18z) is particularly concerning as it shows a strong low pressure system running right up the spine of the appalachians Tuesday night and into Wednesday.

Gfs_op_apcp_f192_us

Traditionally, this is a good snow track for Kentuckiana and snowfall plots from this run show a large stripe of heavy snowfall running from along the Ohio River and up into Central Indiana.

Gfs_3hr_snow_acc_east_65

The hi-res 12z run of the EURO is showing a similar scenario.  This close up snowfall plot centered over Indiana shows a massive swath of 12"+ snowfall from near Scottsburg to Lafayette along I-65 (a distance of about 150 miles).  

The brighter pinks in the plot would represent between 15 and 18 inches of snow.  That would be an absolutely crippling snowstorm for the Hoosier State.  

1779761_10203107139858206_832998019_n

Now before you go running to the grocery to stock up on milk and bread, know that this system is still a week away and is located thousands of miles from here.  

With that said, it's not too early to be talking about potential tracks.  Below I've plotted the last two runs of the EURO (Generally more reliable than the GFS at this range) with the southerly track being last night's 00z run and the northerly track being this morning's 12z run.  

StormTrak 1

Last night's run brings the low from Southern MS into the Southern Appalachians near Chattanooga, TN and then off the East Coast.  

This morning's run brings it MUCH FURTHER north with the track going from Northern LA right up the Ohio River near Louisville and then into the Eastern Great Lakes.

So what does this mean???

A simple distance calculator will tell you that the distance between Chattanooga and Louisville is roughly 250 miles.  This means, that even if the snow is as robust as what the latest Euro says (See Above), then the margin for error on who sees the signficant snow is HUGE!!!

The fact of the matter is that the potential is there for us to see either very heavy rain, significant icying, heavy snow or all of the above. 

Obviously we'll be watching this very closely in the days to come.  

Marc addresses the potential for flooding and snow below...

Meteorologist Jeremy Kappell

 

 

Could This Be A Big Problem For Our Area? - By Marc Weinberg

 

Flooding Potential?

 

Jeremy and I have chatted a lot about this storm system. The amount of precipitiation coming out of this storm, whether it is rain or snow, is impressive. The latest GFS and EURO show about 3" - 4" of liquid falling from this storm. The GFS paints a massive 3" rainfall total over Kentucky, and on ground that is frozen nearly 2 inches down, this could cause flooding and flash flooding in our area.

 

Gfs_long_range_1

 

 

Pinpointing that area this far out is not possible, so we will monitor this.

 

 

Snow Potential?

 

The EURO and the GFS popped out big snowfall predictions for next week in their runs earlier today. To be honest, we see this all the time but in the age of the internet, people will fire the raw data to the public and cause panic. Normally I would avoid this conversation this far in advance, but with so many talking about it, I felt we should address this risk of a big snow in our area next week.

 

What we know is that we do not see significant snow in the Ohio Valley when there is significant southerly flow about 1 mile above the ground. This is an absolutely critical point to discuss with this storm. In my research, we need an easterly to northeasterly flow just 1 mile above the ground to see significant snow in the Ohio Valley. As we look at the data, we need to ignore their snowfall totals and instead focus on the actual raw data to make our own estimation. Let's look to see the direction and strength of the wind at that critical level of 1 mile above the ground on Tuesday / Wednesday of next week.

 

EURO Wind Flow 1 Mile Above The Ground Late Tuesday

Notice the EURO shows powerhouse south-southwesterly winds just 1 mile above the ground on Tuesday. This kind of wind will almost always leads to the data trending WAY warmer as we close in on the storm. We also notice the critical ENE wind that is favorable for snow in our area is in central Indiana.

 

EURO 850 Temp 2

 

GFS Wind Flow 1 Mile Above The Ground Late Tuesday

Notice the GFS has brutally strong south-southwesterly flow at this height late Tuesday. The winds on the GFS are nearly 100 mph just 1 mile above the ground late Tuesday. This means an enormous warm surge in the lower levels and the data will likely get warmer in the coming days. The GFS has that critical ENE wind that is favorable for all snow in far northern IN for Tuesday / Wednesday of next week.

 

 

Gfs_850_1

 

This means the front side of this storm prefers rain regardless of what the computer models show right now. The next question is could this storm produce any significant "wrap around snow"?  This is strictly dictated with how fast the storm will move. Notice the data shows this storm is a very fast mover.

 

Gfs_500_1

 

Historically this means we normally don't see huge "wrap around snow".

 

 

My Thoughts On Precipitation Type -- By Marc Weinberg

 

The GFS and EURO computer models spit out some significant snow in our region in the middle of next week and it ignited a firestorm online. I always say computer model data does NOT dictate the future and it is my job as a meteorologist to interpret it. The model may say snow, but it is critical to determine the type of precipitation as a meteorologist rather than taking a computer model's word for it.

 

As we see this storm right now, almost all the data shows a massive southerly flow just 1 mile above the ground for nearly our entire area late Tuesday and Tuesday night. In a scenario like this, almost every single time the temperature profile will warm more and more as the storm approaches. I cannot count the times I have heard people say "the data is coming in warmer and the snow potential is going down". In reality, what happened is the pattern supported a warmer storm and the data is simply catching up to what meteorology dictated all along. The climatology of a storm like this prefers the heaviest snow from Indy to northern Indiana and it could be a lot. For us, it appears to be mainly rain on the front of the storm with potentially flooding rain or even ice is possible.

 

As the storm passes Wednesday morning, it could produce some snow on the backside of the low or "after the front passes". On a fast mover like this, we normally see limited amounts of backside snow, but it is still very much worth watching. I don't see this as a monster snow for our area right now, but some snow on the back of the storm is entirely possible. This is something we will watch closely.

 

To us, the main threat appears to be flooding rain and windy conditions for Tuesday / Wednesday of next week.

 

Meteorologist Jeremy Kappell

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Comments

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I was talking to some friends at work and we are all talking about the forecasts coming from various outlets. The 1 thing all forecasters have in common is that you all use computer modeling to make up your forecast. Problem is that rarely are any computer models remotely accurate. That being said I have a challenge for you or anyone at WDRB. I challenge you to come up with a 7 day forecast. Here are the conditions:

- You can have no input from any person.
- You cannot use any forecasting software.
- You can only use available current data.

If you get are 80% or better correct I will pay for lunch for you on a day of your choosing.

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