Two mid-level pieces of energy from the Northwest and southwestern Canada will phase together into the mid-level low early next week, which will then allow for a surface low pressure to form over the Midwest by Wednesday. With the moderately-strong jet stream punching through the warm sector of this storm system as well as a strong low-level jet and some instability, the threat for severe weather will exist in the Midwest midweek.
By Monday evening, a few showers and thunderstorms will work from the Northwest into the Northern Plains, although no severe weather is expected to occur.
It’s not until Tuesday when a few strong to severe thunderstorms may take place, especially in the Upper Midwest. Otherwise, a few showers and thunderstorms will be present in this region as well as in the Northern and Central Plains as the surface low pressure slowly develops.
The best chance for severe weather will be on Wednesday now that the surface low has developed. Rain and storms will mainly impact the Midwest region, including cities like Minneapolis, Chicago, Des Moines, and Saint Louis. Based on the most recent data, the jet stream winds at 300 mb (30,000 ft) will be coming out of the southwest at up to 70 mph while the low-level jet at 850 mb (5,000 ft) comes out from the west or southwest depending on your location. Winds at this level of the atmosphere may exceed speeds of 50 mph. This increase in wind speed tells us that the ability for rotation in any of the thunderstorms is possible, which may allow for a few supercell thunderstorms and tornadoes. In terms of humidity and instability, these levels will be on the lower end of the scale in terms of conduciveness for severe weather. The best “juice” for these storms will be a bit farther south.
On Thursday, rain and thunderstorms may work eastward into there eastern Great Lakes region down toward the Ohio and Tennessee River Valleys. All of the ingredients needs for severe weather, including wind shear, instability, and moisture will be on the lower end of the spectrum, but there may still be enough for some stronger storms.
By Friday, much of the precipitation is expected to dissipate ahead of the low pressure’s cold front as the front zooms toward the Northeast.
Again, it is very early is time to discuss specifics, so stay tuned for additional details from WeatherOptics.