Potential big system early next week…but rain or snow?

This is still a few days away but several models have consistently forecasted a pretty big system moving through the Great Lakes region in the Sunday evening or Monday morning timeframe.  However, the inconsistency within each of the model runs has been the track of the system. 

A few days ago the system was forecasted to travel through the northern parts of Lower Michigan, which would give southeast Michigan rain.  During the past day or two, the model runs were forecasting the system further and further south, putting southeast Michigan in a more favorable position for a possible snow event.  However, the most recent model run has repositioned the system further north, thus giving us rain again.

Looking at the top-right and bottom-right images on the image below from last night’s GFS model run, the top image shows the center of the low pressure system tracking through northern Indiana/Ohio which puts the rain/snow line (black solid line on bottom-right image) right through northern southeast Michigan.  This still would give most of us a rain event, but it could be ice as well.  Also, if the trend of dropping the low further south continued as it has been the past few days, we would be in a favorable position for snow. 

Image courtesy of PSU ewall (click on image to make it larger)

This isn’t the case though as shown on the top-right image on the image below which is from this morning’s GFS model run.  It shows the center of the low pressure system much further north, tracking into northern Lower Michigan.  This results in the rain/snow line being much further north, thus giving us an all rain event.  Not only did the GFS morning model run switch to a more northern track, but the NAM and Canadian models did as well.

Image courtesy of PSU ewall (click on image to make it larger)

What does all of this mean right now?  Nothing much.  The upper-level energy that is going to make all of this happen is still currently over the Pacific Ocean, which is represented on the image below.  Until the energy moves over the U.S. and meteorologists are able to get some sample data, it is difficult to forecast with any certainty the path.  It looks that the upper-level energy will be over the U.S. in the next day or two, so I will write another posting after that happens and there is more confidence in the track of the system.

Image courtesy of University of Washington