Southeast Michigan is currently under a winter storm watch for Sunday afternoon into Monday morning. I would expect a warning to be issued sometime tonight or tomorrow morning for most of southeast Michigan, with ice instead of snow being the big concern.
An upper-level wave that is currently over California will produce a surface low east of the Rocky Mountains. Both the upper wave and surface low will quickly move across the U.S. and reach the Midwest during the day on Sunday. This will cause the precipitation to move into southeast Michigan during the afternoon hours on Sunday and last into Monday morning. What makes this system a difficult forecast is due to the low-level jet that will develop at 850mb that will advect warm, moist air into our region. At the same time, colder northwest winds will blow at the surface thanks to high pressure in Canada which should keep surface temperatures at or below freezing. With temperatures in the lower part of the atmosphere above freezing and the surface temperature below freezing, we can expect sleet and/or freezing rain. This is because the precipitation will fall from the clouds as snow, melt into liquid as it reaches the layer of air above freezing, and then freeze again as it reaches the layer of air just above the surface that is below freezing. What will determine if we receive sleet or freezing rain is the depth of the layer of air that is expected to be above freezing and how close it gets to the surface. Locations north of Flint is expected to have all snow and areas near the Ohio border can have periods of all rain. In between can be a mix of different types of precipitation.
Looking at the image below, it shows the forecasted precipitation type for Sunday evening. The top-left image shows the probability of snow, the top-right image shows the probability of rain, the bottom-left image shows the probability of ice, and the bottom-right image shows the probability of freezing rain. The colors represent the probability of each occurring with the darker colors representing a higher probability for each precipitation type. The image shows that the highest probability of snow is north of Macomb County, with a layer of ice pellets and freezing rain expected southward towards the Ohio border.
Image courtesy of PSU Ewall
The first image below show the forecasted position of the center of the low pressure system in Iowa on Sunday evening and the black arrow loosely represents its projected path and the second image shows the amount of precipitation expected.
Image courtesy of HPC
Image courtesy of HPC
This will definitely be an interesting storm to follow.
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