Monday Night / Tuesday Storm ... Rain Or Snow? Some Data Suggests Snow Accumulations!
I think you will probably hear a lot about the storm system Monday night / Tuesday in the coming days. Partially because we are nearing the end of winter (so not many snow chances left) and partially because some of the data suggests some snow for our area. In this blog, I will go through a the details for this storm and if any snow is possible for our area.
Discussion Of Storm Monday Night / Tuesday
The data dramatically moved the storm coming in Monday night / Tuesday much further south and that will ignite a lot of discussion on this storm system. It means snow is in play for our area and this will probably be the big point of discussion over the next 5 days. The EURO and GFS both move the upper level low now to our south Monday night / Tuesday morning. The GFS is slightly further south than the latest EURO.
GFS Mid Level Disturbance Early Tuesday
Notice the GFS is moving this low now through NW Arkansas by early Tuesday. This is a significant shift to the south on the latest GFS.
EURO Mid Level Disturbance Early Tuesday
Notice the EURO is moving this storm further northeast and drives it right across northeast Arkansas. This would be a big more favorable for precipitation in our area.
With the different tracks, one would expect to see the precipitation in different areas early next week and that is exactly what we see. Notice the GFS never gets any precip to Louisville, while the EURO brings the light precipitation well into southern Indiana.
GFS Precipitation Monday Night
Notice the GFS never really gets anything to Louisville, but does bring the potential for accumulating snow to southern KY.
EURO Precipitation Monday Night
Notice the EURO paints an area of precipitation across the heart of our area.
These track differences have a direct impact on snowfall potential in our area. Notice the GFS shows the only real snow accumulations in southern KY for our area while the EURO brings a couple of inches of snow into the metro area. Keep in mind the name of the computer model is on the top right part of each image.
Ok, so we have track differences and resulting snow differences in the computer models. If you read my blog regularly you know that noting the differences is not where my blog ends, but this is where my blog begins. Why are these differences here and which (if any) of these computer models is right? Let's explore that question!
Why The Differences In The Data Today?
The storm we are talking about is nearly 1600 miles off the west coast, so this storm is a LONG distance from our area.
We have seen the computer models shift the track of this storm considerably over the last 24 hours and that should be expected to continue until the storm gets into the US grid of upper air observing stations. That will happen sometime early Sunday. The GFS shows a further south track, but to be honest the consistency between the EURO and GFS over the last 24 hours is quite good. I still am not 100% sold on the track though because normally a storm like this will not track so far south. This track got me searching and I needed to figure out why the change! I know that how far south this storm will track is specifically be determined by the strength of the "blocked" low in the northeast US and that is not clear at this point.
If you recall, the blocking pattern is creating by the negative NAO (North Atlantic Oscillation) and it is very interesting to note the clear error in almost all of the computer models now with the NAO. Remember a highly negative NAO creates a blocking pattern over the north Atlantic. What you see in the graphic below is the negative NAO phase appears to be ending quicker than the computer models think. You can see that in the latest forecasted NAO by the ensembles of computer models. Notice my arrow showing a quick drop when the line turns red meaning the computer models are going negative too fast. This error is noteworthy because if the NAO is not as negative as the computer models think then this storm could track considerably further north.
My Thoughts On Snowfall Accumulation Potential Monday Night / Tuesday Morning
Obviously there is considerable complexity and some answers that I cannot give right now in the long range. The specific track on this storm is critical because the temperature profile of the atmosphere is marginal to support snow in our area Monday night. This storm would have to literally take a perfect track for us to get accumulating snow. With so much uncertainty right now and the questions with regards to the NAO forecast, I would say that an accumulating snow for Louisville is still a long shot.
As I look at this storm a few things pop out to me. For Louisville to get real snow from this storm, it would have to track slightly further north and it would have to arrive in the exact coldest part of the day. There are no compromises on the time at all. If it tracks further north, then we have more warm air over most of our area. If there is more warm air, then we would trend toward rain mixing with snow. As I see it right now, I would be more concerned about southern IN getting accumulating snow than I would be for Louisville but that is still highly questionable. Specific locations are impossible to pinpoint at this juncture, but we will be watching very closely. You know the areas of interest now on this storm and we will be clearing up that picture in the coming days.
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