Potential Snowstorm- Tuesday-Wednesday

As I mentioned last week, there is still a potential for a decent snowfall for parts of southern Michigan, NWOH, and northern Indiana. However, this setup is much more complex than originally expected. I've been updating everyone on the chat bar to the right of this post for several days now.

What has happened is a very strong upper level low (seen below) cut off from the main trough. This has stayed fairly stationary today, but is expected to move generally northeast throughout tomorrow and overnight.

As this upper low moves to the northeast, a surface low is expected to track from the TN valley to the Ohio/PA border:

Now, usually this is an ideal spot for a significant winter storm for Western OH, North/West IN, and Southeast Michigan. However, this will not be the case for this storm. Due to the fact that this upper low comes from the southeast, plenty of warm air has already settled into the area. However, this is a very, very shallow layer of warm air, located within the lowest 150mb of the atmosphere. However, there are already questions with model predictions, because high temperatures today struggled to be reached.

Now, lets look at a few certainties for tomorrow:

1.) Precipitation will be almost all rain tomorrow morning/early afternoon
2.) A surface low will track east of the area, right around Erie PA
3.) The models have trended east in the past couple days.

Now, here's a few uncertainties:

1.) Will snow changeover to rain? If so, when?
2.) Where will the snow first begin to fly?
3.) Will ground temperatures limit accumulations?
4.) Is the cold/warm air still not forecasted correctly?
5.) How much snow will areas receive?

Unfortunately, many of these questions will not be answered until the event itself starts. There is still a decently large model spread between NCEP models and Global Models. The NAM has continued to rapidly shift to the east, giving Toledo 5" of snow based on raw BUFKIT numbers. The GFS, while also continuing to go to the east, still has north-central IN to Flint, MI as the heaviest snow swath.

What really throws a wrench into things is the ECMWF and UKMET. By far the most consistent models for this storm, the ECMWF has also slowly trended east, but much further east than any NCEP model. Shown here, and on AccuweatherPro ECM maps, the ECMWF has over 1" (liquid equivalent) of frozen precipitation for Fort Wayne/Extreme NWOH into SEMI. Based on accupro maps, the ECMWF shows a widespread 4-8" and even up to 10" plus in some areas. Below is an image from the link shown earlier this paragraph:

Another thing to note is the GGEM/RGEM from Environmental Canada (Their version of the NWS) show an earlier changeover to snow than the GFS/NAM, suggesting a bigger snow potential as well. The UKMET also appears to show something similar, while the GFS Ensembles also look to produce more snow than the operational.

For those looking for an easy forecast, shield your eyes from this storm. This is an extremely complex weather system, that likely will throw surprises at us even as we come ever closer to this possible snowstorm. Local meteorologists, NWS offices, and the HPC all seem to have different opinions, just as the models do. There are a few wildcards to watch, such as the amount of dynamic cooling that occurs in heavier precip, as that could cause an earlier switch to snow. Also, ground temperatures are going to be interesting, considering the amount of moisture in the soil right now. Sometimes heavy snow can accumulate quickly on a once warm and wet surface, and other times it does not matter.

I wish I could have a definitive answer for those reading this, but I honestly don't. My gut says that Fort Wayne to Flint gets the heaviest snow, likely over 4", while those east and west of there get slightly less. My preliminary forecast (take with a grain of salt) is 3-7" for NWIN/Southern MI, while NWOH gets 1-3". This could change a lot over the next 12-18 hours, so don't expect this to be a perfect forecast. I will likely be on and off the live chat for much of the night, so if you have any questions, don't hesitate to ask.

Anyways, this looks to be an exciting 36 hours!