We will see our first accumulating snow of the year for many in our area this weekend. As always, the location of that rain-snow line will be critical to determining how much snow you will see in your area and tonight I want to discuss the coming storm. As I am sure you guessed, there are some complexities since the storm is over 2 days away, but let's go through the latest data.
Sunday Night Snow Potential
The complexity regarding the storm on Sunday night has a lot to do with the location of the actual storm system. We will see a complicated "phasing" of the northern branch and southern branch of the jetstream on Sunday that will allow a storm in northern Canada to combine with a storm over Washington state. The storm in northern Canada is nearly 2500 miles from our area and no where near the US right now. Until a storm enters the US, it is not within the upper air observing stations of the US and the data can be unreliable at times.
Since the storm is a LONG way from our area, we are still seeing some variety in the data. The GFS and EURO computer model show the rain-snow line near the river on Sunday night. I have highlighted the approximate rain-snow line with a white line on the GFS map for Sunday night below.
The NAM computer model is running warmer and shows the rain-snow line near our northern counties in southern/central Indiana. The NAM computer model solution would lower the threat of accumulating snow for the city. Again, the approximate rain-snow line is highlighted with a white line.
With the differences of the loation of that rain-snow line, the snowfall totals are obviously very different in the data.
Computer Model Snowfall Output
With the colder solutions showing up in the GFS and EURO, we see considerable higher snowfall totals while the warmer NAM shows less. For what it is worth, the EURO and GFS do tend to over forecast snowfall totals because of some of their weak resolution in the lower part of the atmosphere.
GFS Snowfall Totals For Sunday Night
EURO Snowfall Totals For Sunday Night
NAM Snowfall Totals For Sunday Night
AdvanceTrak Snowfall Totals For Sunday Night
My Thoughts On Snowfall Accumulation Potential Sunday Night
I always say this... there is never an easy snowfall forecast for our area. As is always the case, dialing in that rain snow line is going to be complex. With the storm of interest nearly 2500 miles from our area, it shouldn't surprise us that there is a variation in the data. Some background on some of the computer models can help you to understand why the differences exist. The EURO and GFS are called synoptic scale computer models and that means they deal with pattern recognition well. However, they are not in their element when low levels drive the train. The NAM is a mesoscale computer model that deals well with storms where a warm surge can occur, but it can be very unreliable beyond about 60 hours and this storm is currently 57 hours or so from our area. Since there will be some warm air trying to surge on the front of this storm, it raises some questions in the EURO and GFS data. At the same time, we are still over 48 hours away from the storm meaning the NAM computer model is not exactly in it's element either. This means, some of the specifics are not immediately clear at this point.
What is showing up in all the data is the warmer lower levels. We will likely reach about 43 Sunday afternoon on our high. This means the lower levels will take some time to cool and may never drop below freezing in the city. There is no question that this will knock down some of the accumulations on pavement and non-elevated surfaces in the city and most of our KY counties. Knowing the low levels will be on the warmer side makes these mid level temperatures critical and this is the specific are a I will be watching in the next few days.
How Much Snow Will Fall?
The fact is a solid 1" - 3" snowfall is likely going to occur in our area late Sunday. The data suggests this will start as all snow or transition to all for southern Indiana quickly late on Sunday. This means you are most likely to catch the more substantial snowfall accumulation. How far south this area extends is still a bit uncertain but I am including the northern side of our counties in Kentucky in this total.
As we get near I-64 it becomes a bit more complicated. I do think it starts as a rain - snow mix in this area then a transition to snow will occur. That transition could occur as early as midnight on Sunday night and as late as around 4 am. As we get closer to the actual event, I will be able to dial that in closely. To be honest, we just don't want to get in the race to be first. Our philosphy is to be the most accurate and will only give totals as the data allows. It appears snow accumulation of at least 1" is likely for the city, but how much more is still tough to say.
Our far southern counties will start as rain and end with some backside snow. I think lower accumulations would be most likely for your area. The exact track of the storm is critical to seeing if you can exceed 1" of snow.
When Will The Snow Fall?
Most of the precipitation will fall in the neighborhood of 10 pm on Sunday night to around 7 am on Monday morning. Since this does fall during the night it will negatively impact travel on Monday morning and could cause some school closures in our area.
Will It Stick?
The short answer is yes. Notice the pavement temperatures in North Central Kentucky are already near freezing so this can stick in particular along and north of the river. Locations south of the parkways have warmer pavement temperatures so your road accumulations would be impacted by the warmer pavement.
Weather Prediction Center Snowfall Forecast...
For what it is worth, the Weather Prediction Center has a 60% chance of greater than 2" of snow falling on Sunday night for Louisville.
The WPC has only a 10% chance of 4" or more snow for our area on Sunday night.
We will obviously be watching the storm closely and as the details become clear, we will update snowfall totals. Please continue to check back as we dial in those totals.
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