A very strong storm system will impact our area Monday and Tuesday, bringing a wide range of conditions with it. First, let's look at the atmospheric setup for this event, then break down what that means for us.
Several key ingredients are coming together for this event, which will bring the possibility of severe storms and heavy rain on the warm side of the storm, then freezing rain and sleet transitioning to snow on the cold side of this system. When we look at the temperature profiles in the lower levels of the atmosphere, we of course have temps in the 60's and 70's across the southeast, and readings below freezing in the upper midwest behind a cold front. A very deep layer of moisture extends from the Gulf Coast of Texas all the way into southeastern Canada, right along that front. Also, winds ahead of the front at the surface are from the south, with winds behind the front from the north. Those winds from opposite directions are providing "convergence" that will provide the lift necessary to produce rain and thunderstorms. In the upper levels of the atmosphere, a big dip in the jet stream is allowing that cold air to sink south from the north, and with that big temperature difference, very strong winds are generated aloft, forming what we call a "jet streak". The front of that jet streak, called the entrance region, will move over our region tomorrow, enhancing the lift in the atmosphere, helping provide the dynamics for thunderstorms to form. In addition, an area of low pressure deep in Texas will ride northeast along the cold front, and begin to close off and intensify as it approaches the Ohio Valley. The exact track of the low is very important, because the farther northward it tracks, it will push the cold side of the storm northward, or if it tracks farther south, then the area of wintry weather pushes south.
Here's what that means for us.....Rain will be certain on Monday, with a few severe thunderstorms possible, mainly south of the Ohio River, where a slight risk of severe weather has been issued by the Storm Prediction Center. The main threat with any of these storms will be large hail and damaging winds.
Another threat with this system is the potential for flooding. Basically all of western KY, southern IL, and southeast MO is under a flood watch for Monday, with the potential for localized rainfall totals of up to 3 inches possible, which could cause flooding in low-lying areas as well as some eventual river flooding.
The cold air will begin to arrive Monday night, and it looks like we will see a gradual change over to freezing rain, then sleet, then snow, from west to east through the night. As of now, it appears that most of the region will see snow or a mix snow and sleet on Tuesday. The heaviest accumulations will most likely be northwest of a line from around Poplar Bluff, through Goreville, IL, and over to Fairfield, IL. In those areas, and initial coating of ice is possible, then anywhere from 2-4" of snow is expected.
Keep in mind that this is a very complex storm system, and that the exact track of the center of low pressure is critical as far as where wintry precip falls. It is very difficult to pinpoint exactly when and where snow will fall and how much will accumulate. Any subtle shift in the track of this system could greatly change the conditions over a short distance. We'll be working hard through the next couple of days to bring you the latest details and give more specifics on snow totals. Check back here tomorrow for additional updates, and be sure to tune in with John, Kyle, and Jennifer tomorrow!
Meteorologist Trent Okerson
