The little storm that could?

There's so much that goes into a forecast that goes beyond what I'm familiar with, let alone have expertise in. I'm capable of keeping up with the glossary of terms and great at learning new things. I've learned an amazing amount just over the last year by reading and listening to experts. That being said, when even the experts aren't sure, sometimes you just have to shoot from the hip and let your gut be your guide.

The latest model data is coming in more in line with what I was seeing last week, though to still a bit weaker of a degree. The models show the storm intensifying quite a bit more than what was advertised even as of this morning, and this appears to be more in line with atmospheric observations. A few things go into this, the first and foremost is the strong cold front which passed through earlier today, sparking wind advisories to be issued throughout the northern/eastern two thirds of the state. This front indicates a more amplified jet stream, and essentially gives more horsepower to the storm which is now developing to our south. As it matures, it picks up more of that energy, deepening, and sucking up more moisture from the south. Likewise, stronger winds are produced at the surface as the storm system rages overhead. With that jet stream amplification comes a more curved track, meaning the center of storm should move a bit further north and west than originally anticipated.

All of this means one thing: more snow likely for Michigan, and potentially stronger winds as well. I could make a super-long posts about the depth of the storm and the relation to the strength of wind, but being that this storm has defied all prediction thus far and doesn't make for a great textbook example of storm development (unless you're trying to learn what factors can screw up a model's forecast like me, in which case it's fantastic), so I'll try to keep it to what's likely to happen based on the latest observations, model data, my general gut feeling, and the gut feelings of more qualified individuals such as Ahmad Bajjey and Mark Torregrossa.

First, RAP mesoanalysis. This is a short range model based on actual measurements taken from weather balloons launched at different times of the day, and is usually the "best" in terms of seeing what's actually happening up there. The most significant factor that I can find here that's different from what the other models have predicted are upper level winds. This makes sense, as this is what steers storm systems and causes them to change track. Taking a look at the 500 millibar (roughly 18,000ft) winds, you'll notice quite a difference between what is actually happening out west and what was predicted by this morning's GFS run for this time frame:

You'll notice in the first image that the jet streak out west points further east/northeast as opposed to what the GFS predicted, which is more east/southeast. In terms of the trough, it has a more negative tilt and there is much more energy feeding into it from the north (look at both images around western Montana). This, to me, is likely the biggest factor influencing the development of this system. More energy from the north means more horsepower to drive it, and the stronger it should get. There's obviously other factors going into it, and I can't be certain I'm 100% correct, but looking at this image, I'd say that the latest model runs may still be low-balling this storm in terms of power, and we may be closer what was being predicted Friday, if not quite yet getting there. Right now, the latest NAM is suggesting winds between 25-35mph in lower Michigan, which to me seems reasonable. This in combination with an overachieving storm could bring some areas close to blizzard criteria, though for what length of time I can't say for sure - I don't think it would be very long, let alone long enough for warnings to be issued. The wind will definitely be a factor tomorrow, though, especially with colder temperatures and fluffier snow.

So speaking of snow:

Latest GFS

Latest NAM12KM

Latest NAM4KM

Based on observations, latest model data, expert opinions and my gut, I'd now say that lower Michigan is probably looking at a wide swath of 6-10" of powdery snow, and that Winter Storm Warnings are likely to come out in a couple of hours. The storm definitely shows a more northernly track than previous forecasts, which would place the Thumb and Tri-Cities in the bullseye for the highest totals. Keep in mind that the above images show a 10:1 snowfall ratio, too. The track of the storm is definitely looking like the type that brings a lot of snow to Michigan, and combined with the temperatures, we could be looking at a 12:1 ratio or higher.

This is one of those scenarios when forecasting the weather becomes more divination and feeling than raw interpretation of numbers. This storm definitely has potential. It's still going to be wait-and-see until the snow starts to fall, and actual observed rates can be calculated.