Sunday's Storm Just Got Even More Complex

When all is said and done, no matter what happens, I don't think Sunday's storm will be one that I, or any other forecaster, will look back on and say: "Wow...I called that one correctly from a long way out." I know looking back on my posts, I was initially unconfident one way or the other. I then became more confident about a snowstorm for SE Michigan. From there, the confidence faded, reaching a low last night when I said that a lot of the precipitation would likely fall as rain, and SE Michigan would likely get only advisory level snowfall, if that. Being that at the time I wrote that post, we were only 60 hours out from the storm, I thought that would be the end of it. It looked like this storm would likely track too far north to give SE Michigan any significant snowfall.

But wait. This morning's model runs came in, and with them comes more hope that this storm will track far enough south to give SE Michigan the potentially significant snowfall that I thought you guys would be sure to see earlier in the stages of tracking this storm. I'm again less certain than I was last night. For being less than 48 hours out from the initial stages of this storm, I can say this might be the most uncertain storm I have ever followed. However, being that we are less than 48 hours out, it's really time to start leaning one way or another w/ regards to how much snow I think you guys are going to get. So, first let's take a look at some forecast models. From there, I will attempt to explain how I will make my forecast for this complex storm system. Finally, I will start to explain the chances for a snow day with this storm. With no further buildup, here we go:

GFS:

The latest run of the GFS has the low pressure system tracking from Chicago to Detroit. This is further south than what this model showed last night, when it had the low pressure system tracking from Milwaukee to Saginaw. This model was one of the more favorable ones for snow in SE Michigan in the first place, and it has only gotten more favorable since then, as it now shows almost all of SE Michigan getting predominantly snow for the entire event. In addition, this model now shows almost all of SE Michigan getting in on some good wraparound snow action, which would boost snow accumulations. As crazy as it sounds, I'm fairly certain that nearly all of SE Michigan would be in for a Winter Storm Warning criteria event if the GFS verified. It shows a long duration snow event from Sunday Morning continuing through early Monday Morning. Obviously this timeframe would be good for a snow day. The image below shows the wraparound band of snow hitting MI Sunday Evening. Note the strong pressure gradient (tightly packed black lines) which would result in strong winds.



ECMWF:

One of the most remarkable southward shifting models has been the ECMWF. The ECMWF has been locked into a northern solution for days, and last night showed a low pressure track from Milwaukee to Saginaw, with much of SE Michigan dealing with precipitation type issues. However, this morning's run of the ECMWF also shifted south, with the low pressure system moving from the Wisconsin/Illinois border to Detroit. I really can't believe I'm saying this, but looking at the data it also appears as though the ECMWF has a nice backside band of snow (the graphics haven't updated yet but the statistical data for the model has) which would result in borderline Winter Storm Warning criteria accumulations.

NAM:

I trust this model a lot in the short range, which is why I am still worried that it still has this low pressure system tracking from Milwaukee to Alpena, as it did last night. This is one of the main things that has me going against a big winter storm affecting SE Michigan this weekend. If the NAM's solution verified, most of SE Michigan would likely be looking at precipitation type issues and Winter Weather Advisory criteria snows at best, (a) because of increased precipitation type issues, and (b) because of the lack of good backside snows unlike what is shown on the GFS and ECMWF. In fact, in the image below, you can clearly see that the low pressure system and accompanying backside band of snow are well north of what is shown on the GFS. And, take my word for it, also north of what is shown on the ECMWF. When the NAM and ECMWF have a similar solution, as they did last night, it is difficult to forecast against them. However, now that they have different solutions, forecasting this system becomes very complex, as both models are usually deadly accurate at this range. In this case though, one of them will be very wrong. The question is, which one?



GGEM:

The GGEM is the furthest south of the models, with the low tracking from Gary, IN to Toledo, OH to Erie, PA. With this model, SE Michigan would likely stay all snow and get some good backside accumulations.

NMM:

The NMM is a High-Resolution model that I like to take a look at inside of 48 hours. This model also goes north, with a low pressure system tracking from Milwaukee to Saginaw, resulting in less snow for SE Michigan.

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This storm is truly a nightmare to forecast. There are two distinct camps of models at this time, the GFS/ECMWF/GGEM camp which has the low pressure system tracking south, and the NAM/Hi-Res model camp, which has the low pressuer system tracking north. Whichever one ends up being correct will affect the storm total accumulations in an extreme way. If the NAM/Hi-Res camp is correct, then much of the precipitation associated with this storm would come in a front end thump of rain/snow resulting in likely only 2-3" for SE Michigan. If the GFS/ECMWF/GGEM camp is correct, then not only would much of the front end thump of precipitation be snow, but SE Michigan would also likely get in the heavy snow on the backside of the low. Snow ratios would be high, allowing for efficient accumulation. In addition, winds would be very strong allowing the snow to blow & drift around. A lot more accumulation would fall, and there would be major blowing & drifting. Simply put, if the first solution happens, you guys would likely not get a snow day. If the second solution happens, you guys likely would get a snow day. It's extremely tough to favor one solution over the other at this time, but in the short range I'm a believer in trends, and I'm really starting to think this will end up tracking far enough to the south to give much of SE Michigan some good accumulations. Therefore, I will up my forecast accumulations for Lake Orion with this storm to 4-8", but also mention that there is a high bust potential with this storm. I will also upgrade the snow day grade to a C (50/50 chance, will increase or decrease as time gets closer). I really believe that the final snow day call will be fairly easy. If you guys get in on the backside snow bands, you'll probably get a snow day, and if you don't, you won't. But while I favor you guys getting in on the backside snow, I'm far from certain on it happening, so I will only upgrade the snow day grade to a "C" for now.

My next post will come tomorrow evening and this one will have a snowfall map, and in all likelihood, a lot more certainty on what will actualy happen. If I had to sum up my thoughts on this storm in one sentence right now, it would be: As opposed to last night, I am leaning towards SE Michigan getting a significant winter storm on Sunday, but it is far from certain.

One thing is for sure, this has been one of the craziest storms I have ever followed. As always, feel free to leave questions/comments in the comments section below.