Our well advertised winter storm has already started in our area. We are seeing a wintry mix from near Bedford, IN and lots of freezing rain and sleet over western Indiana. Temperatures are cooling fast and we have a rough 24 hours ahead of us. Time to dive into this discussion.
Winter Storm Tonight / Friday
We are seeing a large ploom of moisture firing out of Oklahoma and moving in our direction. This is a huge area of rain/snow/freezing rain/sleet and it is all moving in our direction. Remember white to blue is snow, orange to pink is sleet / freezing rain, and green is rain.
Notice the precipitation has changed to sleet and freezing rain northwest of Bedford, IN as of 8 pm and that line will spread across the area tonight and Friday.
The temperatures are critical and I noted in my earlier newscasts that the computer models were not handling the cold terribly well. They are running a couple degrees warmer than what we are seeing and that means the transition to sleet and freezing rain will happen faster than what they are predicting.
AdvanceTrak has been doing a pretty good job of handing the waves of precipitation that will move through. It looks like a heavy pocket tonight, a lul near 3 am, then it will go heavy tomorrow mid morning through late in the day. It shows the transition line to wintry mix and snow gradually moving across our area on Friday. Notice the very fast transition to snow for our northern and northwestern counties, the transition to sleet early on Friday for Louisville, then to snow for the metro on Friday afternoon. As you look at the data, please keep in mind that the timestamp is on the top right part of each image.
The computer models are spitting out a little less snowfall today than yesterday... well other than the bullish EURO computer model. I have been saying for days that the EURO needs to be discounted since it doesn't deal with low level meteorology well and I still think it is bunk. The NAM captures our northern counties well, but not along the river. The GFS seems to have a better overall feel, but is too low for our northern counties. AdvanceTrak seems to have a pretty good handle on snowfall amounts on this latest run.
GFS Computer Model Snowfall Forecast Through Late Friday
EURO Computer Model Snowfall Forecast Through Late Friday
NAM Computer Model Snowfall Forecast Through Late Friday
AdvanceTrak Computer Model Snowfall Forecast Through Late Friday
My Thoughts... When The Changeover To Wintry Mix Occurs & Snow/Ice Accumulations
With this big mess heading in our direction, the NWS has a Winter Storm Warning for a good chunk of the area including Louisville starting at 10 pm tonight and going until midnight Friday night. Most of our southern counties are in a Winter Storm Watch, but the NWS will upgrade that to either a Winter Storm Warning or Winter Weather Advisory tonight. The NWS has told me they will wait until the late data rolls in before deciding.
Let's start by talking about the pavement. For any frozen precipitation to stick to the pavement, we need road temperatures either near freezing or a LOT of wintry precip. The pavement temperatures are cooling, but they are warm enough that they will knock some of the accumulations on roadways down. This obviously adds difficulty to an already difficult forecast.
I had a question yesterday about what is the difference between sleet and freezing rain, so let me quickly answer that. Sleet is ice pellets falling from the sky and freezing rain is liquid rain that freezes on contact. Freezing rain is absolutely toxic!
With that understanding, let's attack when the transition from rain to freezing rain to sleet to snow occurs. This transition will occur very quickly in our northern counties and gradually move southeast over the next 24 hours. As mentioned above, we are colder than all the computer models say and that was expected, so we cannot trust their timeline.
- Northwest Counties Including Seymour, IN to Bedford, IN to Paoli, IN to Bedford, IN - I think we are all snow in our far northern counties by around 10 pm - 11 pm tonight.
- Southern Indiana Including Salem, IN to English, IN to Scottsburg, IN to Madison, IN - Sleet or freezing rain is likely from now forward. You should go to all snow around mid to late morning on Friday.
- Areas Along The River Including Hardinsburg, KY to Louisville, KY to Carrollton, KY - Changing to sleet/freezing rain by around 2 am - 5 am early Friday. Changing to all snow from around 4 pm on Friday.
- South Central Kentucky Counties Including Leitchfield, KY to E-town, KY to Bardstown, KY to Springfield, KY - Changing to sleet/freezing rain around 7 am - 10 am on Friday. You should end with snow but it will take until late afternoon for you.
- Southeast Counties Including Munfordville, Greensburg, to Columbia, KY - Mainly rain for the duration of the first storm. Changing to light snow or sleet around 7 pm on Friday.
That covers the when, now let's cover how much. It is pretty clear that our northern row of counties will get the highest snow for our area. As we get to the river, we will see quite a bit of sleet accumulation before the snow gets here. For example, Louisville will likely get 1" of sleet before the change to snow at 4 pm. That gives the city about 4 to 5 hours to catch a snowfall accumulation. In southern KY, the transition comes so late that heavy rain is your greatest threat. Here are my specifics
- North Vernon, In to Seymour, IN Bedford, IN - 4" - 8" of snow
- Paoli, IN to Salem, IN to Scottsburg, IN to Clarksville, IN to Madison, IN to Carrollton, KY - 2" - 5" snow with up to 1" of ice.
- Louisville, KY to Hardinsburg, KY to Frankfort, KY to E-town, KY - 1" - 3" of accumulation of ice and snow. Note... I think we will see about 1" of sleet accumulation.
- Leitchfield, KY to E-Town, KY to Munfordville, KY to Springfield, KY - Up to 1" of sleet accumulation. You will see a ton of rain before the transition occurs.
- South of these areas are mainly rain, but we could see rain totals up to 3" in our area.
I urge caution when looking at snowfall or ice totals. These are RANGES, so please do not focus on the top number and you will have a reasonable expectation for your area. This system is going to cause a lot of problems. The snow will be heavy at times late tonight and through the day for our northern counties. The sleet will be very heavy in Louisville from around 9 am - 4 pm. Our southern counties will change later, but you will see still see sleet accumulation and icing. Road conditions may not be bad when you wake up in particular in Louisville, but at some point the heavy sleet will take its toll in the late morning or early afternoon. Driving late on Friday could be difficult in spots. Please use caution.
Lastly, we will drop to around 20 degrees Friday night and anything that is wet will freeze. This is what we call a "flash freeze" because it will go from wet to frozen nearly instaneously. This can be absolutely treacherous, so please use real caution driving late on Friday night or Saturday morning.
Sunday Storm System
We continue to see changes in the data regarding Sunday. I have warned all along that making specific statements about Sunday would be unwise until we get this first storm through. The data is slowing the storm down a bit on Sunday and showing two distinct waves of precipitation... one in the morning and another late Sunday night. The first will be wintry and the second is tough to say right now. The GFS and NAM show a cold enough profile for possibly snow on the northern edge Sunday morning and that has been a trend in the data. We have also seen the storm pushed further south in the latest data and that is likely because the computer models are starting to figure out how cold this air mass really is. The GFS shows the first wave on Sunday as mainly snow for Louisville and freezing rain near the KY parkways. You can see the precipitation type from the GFS in the data below with the legend on the right of each image. Notice the timestamp on the top right part of each image on the GFS computer model.
My Thought's On The Sunday Storm System
I still think the computer models are a touch too warm, but they are getting better on Sunday. It does appear the mid levels will be cold enough to support snow on the northern edge, but where that northern edge ends is in serious question. The latest data shows Louisville in several hours of snow early Sunday before going to freezing rain. The problem will be where that snow line ends and where the freezing rain line begins. I still think significant icing may occur in parts of Kentucky with this initial precipitation early on Sunday. The second wave of precipitation late Sunday could end up bringing icing to Louisville or southern Indiana. In all, icing of 1/4" to 1/2" are possible, but that location remains unclear. I also feel a 1" - 2" snow is on the table on the northern edge of that morning precipitation, but again feel the location is still unclear. We will watch it VERY closely in the coming days.
It is winter storm season and if you want to be one of my storm spotters, you can join me on my facebook or twitter page. Just follow the link below and click "like" or "follow".
If you ever have any question, please remember I can be reached on facebook or twitter easily! Just follow the link below to my facebook or twitter page and click "LIKE/FOLLOW"!