FXUS63 KLOT 152346 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 646 PM CDT Wed Apr 15 2026 .KEY MESSAGES... - Additional period of showers and thunderstorms expected this evening. Some could be strong and produce heavy rainfall leading to localized flash flooding. - A brief break in the pattern is expected late Thursday into the day on Friday before another storm system arrives Friday evening into early Saturday. - Cooler air arrives into early next week and may bring frost/freeze concerns early Sunday and Monday mornings. && .DISCUSSION... Issued at 257 PM CDT Wed Apr 15 2026 Through Thursday... The primary weather focus in the near continues to revolve around the expectation for additional rounds of showers and thunderstorms, particularly this evening. A recent surface analysis indicates that an area of low pressure resides across southeastern NE, with an associated surface cold front extending south-southwestward into the TX Panhandle. While our area has remained cloudy, increased insolation west of the area in the vicinity of the surface low and frontal boundary continues to destabilize the very moist (dew points in the low to mid 60s) low-level prefrontal airmass across MO into south central IA. This will set the stage for additional thunderstorm development mid to late this afternoon west of our area as increased forcing for ascent associated with the mid-level impulse ejecting into the Mid-Missouri Valley overspreads the frontal boundary. After storms onset, a gradual upward growth into an MCS is anticipated this evening as they shift eastward across the Mississippi river. It appears the primary severe weather threat with these storms will be west of our area, with storms likely to be on a weakening trend as they progress eastward across northern IL during the mid to late evening hours. Nevertheless, a continued favorable kinematic environment overhead may continue to support a threat for localized strong wind gusts with the weakening line of storms. Heavy rainfall is expected to accompany these storms through the evening, and this does continue to add concerns for possible hydro concerns tonight. However, it appears the heaviest rain rates may remain more progressive with the moving line of storms tonight. Accordingly, it appears the threat for significant flash flooding is lower than previously thought. Nevertheless, areas across far northern IL that received heavy rainfall last night will be most at risk for additional flooding concerns., With this in mind, we have opted to hold onto the going flash flood watch for this evening. Shower and thunderstorm coverage is expected to become more widely scattered overnight tonight into Thursday as the main mid-level impulse shifts overhead. As an afternoon lake breeze develops and pushes inland across northeastern IL and northwestern IN Thursday afternoon in the wake of the surface low, this may act as a focus for additional isolated shower activity for a few hours Thursday afternoon. Outside of this, conditions will be drying out Thursday afternoon and evening. KJB Friday - Saturday: Strong southerly warm and moist convection will return into the day on Friday ahead of an approaching cold front. This boundary is expected to progress across the area sometime late Friday into early Saturday morning paired with a line of thunderstorms, some of which could be severe. Suspect that less favorable diurnal timing of any lingering storms into the morning on Saturday may limit the overall severe threat here locally before storms reintensify east of the area into the rest of the day. Stay tuned! Saturday night onward: In the wake of the early Saturday cold front, a much colder airmass (relative to what we have had over the past several days) will settle into the region over the weekend. Overnight low temperatures may drop into the 30s, with some near to sub- freezing temperatures possible across interior northern Illinois. Lighter winds in place Sunday night may allow for frost development outside of Chicago and will be something for those with agricultural interests to monitor over the next few days. The cooler conditions will be rather short-lived with extended guidance favoring a return toward high amplitude ridging across the central CONUS and unseasonably warm temperatures returning to the region by midweek next week. Petr && .AVIATION /00Z TAFS THROUGH 06Z FRIDAY/... Issued at 646 PM CDT Wed Apr 15 2026 Forecast concerns include... Scattered thunderstorms this evening. Possible wind shift to east/southeast behind storms. Mvfr cigs/periodic showers overnight through Thursday afternoon. Wind shift to northeast early Thursday afternoon. Current showers and a few thunderstorms over far northwest IL are expected to slowly increase in coverage over the next few hours and form a broken line and move across the rest of the area during the late evening hours and likely be weakening some as they move across the Chicago metro area. Current tempo timing seems on track for the Chicago terminals with perhaps a few showers prior to this activity. Additional showers are expected in the early overnight hours with additional showers possible from mid morning Thursday through early Thursday afternoon. South/southwest winds may gust as high as the mid 20kt range this evening with directions perhaps favoring more southerly for the next few hours then turning more to the southwest by mid evening. Confidence is low for wind directions behind the expected area of thunderstorms later this evening. Some of the most recent guidance turns winds southeasterly and opted for a 170 direction for now, but changes to winds can be expected with later forecasts and updates. Winds will turn more southwest by daybreak, westerly Thursday morning and then shift to the northeast as a lake breeze/front moves inland. Early Thursday afternoon timing looks good but specific timing will need some refinement as trends emerge. Mvfr cigs will be possible with any showers or thunderstorms this evening then prevailing mvfr cigs are expected to develop overnight and continue through early afternoon Thursday with some uncertainty for how fast cigs may lift during the afternoon. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Flood Watch until 1 AM CDT Thursday for ILZ003-ILZ004-ILZ005- ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020- ILZ021-ILZ023-ILZ032-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107- ILZ108. IN...Flood Watch until 1 AM CDT Thursday for INZ001-INZ002-INZ010- INZ011. LM...None. && $$ Visit us at weather.gov/chicago