Last night’s snowstorm brought different conditions depending on your location. The southern two-thirds of southeast Michigan received between 6-8 inches of snow, while the northern third received between 8-12 inches. Click here to see the totals across southeast Michigan. You can also see the totals on the map below.
Image courtesy of NWS Detroit
There are a couple reasons why most of southeast Michigan didn’t receive the snow totals originally forecasted. The first and most important reason is because the center of the low pressure system ended up moving further north than originally anticipated. The first image below shows the center of the low pressure system at 4am. The black arrow represents the direction the low moved, and the end of the arrow represents its position at 7am. This track resulted in the dry slot moving further north into southeast Michigan, thus giving some locations a break from the snow. The second image below shows the water vapor image at about 5am, where you can see the drier air has pushed into parts of lower southeast Michigan as a result of the low’s position.
Image courtesy of HPC
Image courtesy of RAP
The radar image below from about 5am confirms this dry air put a temporary stop to the snowfall. The snow did pick up again a few hours later as the back end of the precipitation moved into our area (represented by the black arrow). Also, the radar image shows that the dry slot didn’t reach the far northern counties of southeast Michigan which is why the snow totals were higher in this region.
Image courtesy of RAP
Another result of the low’s center making it into northern Ohio was that the precipitation changed from snow over to sleet/ice. I know that the sleet occurred as far north as northern Macomb County since it was sleeting when I was outside around 1am last night. The surface temperatures were around 20F during the evening which is too cold for sleet, but a few thousand feet above the surface the temperatures were above freezing. The image below is a sounding and it shows the temperature, dew point, and winds from the surface to the top of the troposphere. The sounding indicates that the surface temperature was about 20F, but there was a layer from 825mb-780mb (5,000ft – 6,500ft above the surface) in the atmosphere that was above freezing (between 32F-35F). So when the precipitation fell from the clouds, it started as snow and stayed that way until it reached this layer where it then started to melt, but as the precipitation fell below this layer, it was back in air below freezing so it froze again. This process resulted in sleet/ice pellets reaching the ground throughout parts of southeast Michigan Eventually as the system moved off to the east/northeast, the colder air moved in and the precipitation in the morning was all snow, but the time period of sleet/ice helped reduce totals.
Image courtesy of RUC
The final image that I am going to show is called a meteogram. The meteogram shows the temperature, dew point, precipitation, winds, cloud data, and pressure data, etc. hour by hour for a given location. I want to point out two things on this image. The first is highlighted in the red box and it shows the wind gusts from yesterday at 2pm to this morning at 6am. You can see that the highest wind gusts were generally between 9pm-1am where the highest recorded wind gust in this period was 28kts (32mph) which is below blizzard warning conditions. Actually, the winds during the entire evening never reached the minimum blizzard warning conditions of 35mph or higher. This meteogram is only for one location and other areas across southeast Michigan most likely did have wind gusts above 35mph. I did hear that Kalamazoo Michigan received wind gusts over 60mph, but I have not yet been able to confirm this. The second thing that I want to point out is in the yellow box which shows the atmospheric pressure during the snowstorm. As the center of the low pressure system moved closer to southeast Michigan, the pressure started to decline. The pressure stayed lower while the center was passing just to our south, and then as the center continued to move further away to the east, the pressure started to increase again.
Image courtesy of UNISYS
So overall, this system was a very impressive and strong system that affected a lot of the eastern U.S. The western half of Lower Michigan received 12+ inches of snow, the Chicago area received over 20 inches of snow with wind gusts as high as 70mph near Lake Michigan! Even as far south as Oklahoma received nearly a foot of snow, and the Dallas area (where the Super Bowl will be on Sunday) received ice and an inch or two of snow! So this was an impressive and powerful system, but unfortunately most of southeast Michigan didn’t receive the totals being mentioned in the days leading up to the storm. Either way this was a nice storm and hopefully we’ll have another chance or two before spring arrives in about a month or so.
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