This weekend will end much like it began with regards to weather conditions. Sunday is forecasted to be a very pleasant day with plenty of sunshine and highs in the low 50s to the north with mid to 50s to the south. Warm Air Advection will continue across the area ahead of the next developing storm system across the western plains. A surface low pressure system will develop along the CO/WY border overnight Sunday and will quickly strengthen as it lifts northeast making it to Central NE by Monday evening. The low pressure is forecasted to begin occluding by early Monday evening and this will help to wrap cold air into the eastern side of the Low pressure system which will impact areas previously in the warm sector of the storm.
The implications of this system for Central IL will be a greater push of moisture northward into the area overnight Sunday into Monday as the low pressure system strengthens. Given that the surface low will remain well to the west of our forecast area this will result in all liquid precip across all of Central IL until well after the frontal passage Monday evening. Expect a light to moderate rainfall event for much of central IL, with the heaviest amounts occurring along and mainly west of I-55. A detailed look at forecast rainfall totals can be seen in the map below.
The remnants of the occluded low will begin to drop southeast and will likely make it to Central IL sometime Tuesday evening. While I do not currently anticipate anything more than light precip, there will still be some moisture associated with the low pressure remnants. Depending on surface temperatures some of this may fall as scattered light snow showers or flurries across portions of the area (Likely across the northern half of Central IL) while the remainder of the forecast area sees all rain or a mix of light rain and snow showers.
The main area of concern during this period will be much colder airmass that will invade Central IL in the wake of this low pressure system. Temperatures mid to late week will be running several degrees below normal for early March. From Wednesday through Friday, expect highs in the mid 30 to upper 30s north with upper 30s to low 40s south, and lows in the upper teens to low 20s north and low to mid 20s south.