Low Pressure System Produces Storms Over Midwestern States (author: Sydney Hopkins)

By Thursday morning, the low pressures system, which was centered over the northern part of Wisconsin, has moved northwest and is now centered over Lake Superior and southern Ontario. As seen in the surface analysis map below, this system is producing an associated cold front, which is producing storms over the Midwestern states, producing the strongest storms over the states of Illinois and Indiana. The system has a minimum pressure of around 993 mb, which is about the same pressure the system had the night before. The pressure gradient around the surface low appears to have strengthened as the isobars have moved closer together. Figure 2 shows a black and white visible satellite image of the system.

Figure 1: Surface Analysis Map 11 Mar 1200Z


Figure 2: GOES-East Visible Satellite Image, 11 March 2021 13Z


Figure 3 shows the GOES-East Infrared Image of the system. This image is overlayed with associated radiative temperature of the system. When viewing infrared images, the whitest regions are associated with the coldest radiative temperatures. This also gives us insight into the cloud height and convective energy of this system. The whitest (coldest) regions on the map indicate clouds that have pushed further up into the atmosphere, which is usually associated with higher convective activity. In the figure below, you can see somewhat cold temperatures associated with the system over the Midwest. This indicates that clouds in this region have pushed higher into the atmosphere, and there is some convective activity associated with this system.

Figure 3: GOES-East Infrared Image, 11 March 2021 13Z


Figure 4 shows the radar image of this system at 13Z. The radar shows a loosely-organized group of storms over the Midwest to eastern US. The strongest storms of this system are centered over Illinois and Indiana, where a squall line can be seen running from St. Louis to just west of Indianapolis. The squall line runs parallel and just out in front of the associated cold front seen on surface analysis map in Figure 1. Overall, the low-pressure system, and its associated cold front, is producing storms with moderate precipitation and intensity.

Figure 4: Radar, 11 March 2021 13Z


Based on the position of the low-pressure system, I believe it will continue to strengthen throughout the day today. It is located between a downstream trough and an upstream ridge. This is an area of divergence and upward vertical motion, which is conductive to the strengthening of extratropical anticyclones, such as this system. On Figure 4 below, the system can also be observed to be in the left exit region of the jet stream, which could also be a source of strengthening for this system. I believe this system will continue to strengthen and produce more organized storms as it moves east to northeast throughout the day.

Figure 5: 300 mb Observation Map, 11 March 2021 12Z