The week started with mostly sunny skies and above average temperatures, but all of this looks to change by the end of the week as a stormy weather pattern begins to take shape.
A large scale trough is forming across the western U.S. and the Central Plains. This trough with send the Jet Stream, a conveyor belt for storm systems, diving through the Southern Plains and swinging north through the Upper Midwest. This will send multiple storm systems through the area through the weekend.
The first system will begin to affect Central Illinois on Wednesday. A slow moving cold front will crawl it’s way through Central Illinois throughout the day with scattered showers and thunderstorms developing along and ahead of the front.
Warm and moist air moving off of the Gulf of Mexico will bring modest instability to the area by Wednesday afternoon. A powerful Jet Stream blowing over 80 MPH will help bring strong wind shear to the region which will allow storms to become strong to severe. The wind shear is largely unidirectional which means the winds change very little in direction with height (southerly winds at the surface, southwesterly winds aloft). With very little turning of the winds at lower levels of the atmosphere the primary threat with any severe thunderstorm will be damaging wind gusts, large hail and heavy rain.
With the cold front moving slowly, multiple rounds of strong to severe storms will be possible. Rainfall amounts through Wednesday will approach 1-2 inches for areas along and east of the Illinois River. Lighter rainfall amounts are expected further west where few thunderstorms are expected to develop.
Once the front moves through, a few rain showers could linger through early Thursday morning. Temperatures on Thursday will be cool as they sit in the mid 50s however, the cool down will be brief. Winds will turn southerly on Friday ahead of our next storm system pushing temperatures back in to the 60s.
The next system will move in over the weekend bringing scattered showers and thunderstorms to Central Illinois. Severe weather is not expected through the weekend but heavy rain could lead to localized flash flooding. When it’s all said and done, rainfall amounts could range from 3-5 inches for portions of the region leading to rising river levels across Central Illinois for the start of May.