Snow Potential For Early Next Week! Let's Dive Into The Latest Data
Yesterday all the computer models dropped the low pressure south of our area for early next week, igniting a lot of chatter about this storm. Remember when a storm moves south of our area, it has the potential to produce accumulating snow in our area. I argued the data from the computer models was flawed for next week meaning that forecast for accumulating snow was highly questionable. Let's dive in tonight and ask some of the same questions.
Early Storm For Next Week -- Discussion
In my blog last night, I said the computer model data was highly questionable because all the computer model forecasts for the NAO were wrong. Was is the NAO and why should you care? The NAO is the North Atlantic Oscillation and it is basically the El Niño of the Atlantic Ocean. When the NAO goes highly negative (like it just was) we see blocking patterns setting up in the Atlantic. These blocking patterns produce cold weather for the eastern US and can stop the progression of storms across the country. Therefore a highly negative NAO would create a block that should push our next storm south of our area and allow cold air to filter into our area. This is where the forecast becomes interesting. Notice the bulk of computer models (red line) show a highly negative NAO for next week. The black line is the past through right now and the red line is the forecast.
The problem is the computer models are all wrong! Notice the red line forecast doesn't even connect with current observation! This is critical to note because without a highly negative NAO, we won't see as strong of a block over the north Atlantic and it means the storm will likely track further north in the coming computer model runs.
With that info in mind, let's look at the data and let's see if the data is suggesting a shift further north. A shift further north would also allow more warm air into the system and limited snow accumulation potential.
NAM Surface Low Monday Night
Notice the NAM has the low over Western KY and almost in southern Illinois Monday night. This is the further north of all the solutions and the warmer. Notice the rain-snow line is nearly in Indianapolis Monday night on the NAM.
GFS Surface Low Monday Night
the GFS is warmer now showing the rain-snow line further north and the low pressure center in western KY. The shift to warmer and further north continues.
EURO Surface Low Monday Night
Notice the EURO is the furthest south and the coldest. The EURO shows the low center of norther Mississippi with the rain-snow line in southern Indiana.
What Should We Believe? My Thoughts!
I hear a lot of people say, I like the EURO or I like the GFS, but I am not a fan of this philosophy. I think we should rip apart the data everytime, find out why each computer model produces it's current solution, and find the truth. My allegiance is not to a computer model, but to accuracy. A few things we know, the NAO forecast is blatantly wrong by almost all of the computer models. This means the data is likely too cold and too far south. Next, the EURO and GFS are what we call synoptic scale computer models, so they do not accel when low level meteorology drives the train. The NAM is a higher resolution computer model and it will deal with low level driven storms the best.
As we look at the current data, we see the NAM is the furthest north, the warmest, and least likely to produce accumulating snow. We also notice the EURO and GFS have continued to drift north and warm. It is important to note, that when a storm starts to drift further north on the computer models in a setup like this, it is a sign that cold air is lacking on the storm and warmer air will take over. Notice how the NAM shows winds only 1 mile above the ground out of the west-southwest at nearly 35 mph shoving a lot of warm air aloft into our area.
The GFS shows this exact same wind at this height, but since it has poorer resolution, it is not quite as warm. This means the NAM is more believable at this juncture. The EURO seems to be suffering from its poor low level resolution right now, so I think it is biasing cold.
For you, this means generally the warmer solution is likely the most accurate right now. I still urge caution in drawing conclusions until the storm gets in the US grid of upper level observing stations on Sunday. Once that occurs, we should see a consolidated solution from the computer models. As things stand right now, the warmer solution means mainly rain on the front of the storm and the only real way to see accumulating snow in our area is from wrap around. This path is normally not the track that produces notable backside accumulations, so the snow accumulation potential is not great for our area right now. I will stand by my forecast for mainly rain in Louisville with the potential to mix with snow on the back of the storm and the potential for Louisville to see snowfall accumulations is not great. The greatest chance for accumulating snows appears to be central Indiana as things stand right now.
If you ever have any questions, please remember I can be reached on facebook easily! Just follow the link below to my facebook page and click "LIKE"!