FXUS63 KLOT 181810 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 110 PM CDT Mon May 18 2026 .KEY MESSAGES... - A few additional rounds of showers and thunderstorms today and Tuesday, some of which could be strong to severe mainly during the afternoon hours. - Summer-like warmth and breezy winds at times will prevail through Tuesday, then cooler temperatures return for the middle of the week. - Milder weather returns heading into the weekend, though with at least intermittent shower/thunderstorm potential. && .DISCUSSION... Issued at 347 AM CDT Mon May 18 2026 Regional radar mosaic shows a linear MCS moving across the Mississippi River into western WI/IL early this morning. There has been a notable weakening trend to the convection over the past few hours as the complex propagates into a region of decreasing deep- layer shear and low-level instability, though storms should continue to spread eastward this morning along a composite outflow boundary at the leading edge of the convection. In fact, recent radar trends indicate a few new cells developing ahead of the line near the Quad Cities, perhaps aided by enhanced ascent associated with one or more an apparent MCVs near the IA/IL/MO border. Gusty winds of 30-40 mph with the outflow and some small hail are possible with these storms early this morning, though the overall threat of organized severe weather appears low for the next several hours. Later this morning however, diurnal warming and associated destabilization along the east/southeast periphery of the complex remnants and outflow boundary may support renewed development/strengthening of convection with more of a severe threat into this afternoon. Though depending on how far the outflow boundary makes it this morning, this would likely be across the south/far east portions of the forecast area. Farther north/northwest, lingering stratiform rain and cloud cover this morning looks to limit destabilization and recent CAM trends have been consistently dry there during the day/evening. Farther to the west, early morning GOES vapor imagery indicates another mid-level short wave rounding the base of a western CONUS long-wave trough. Widespread strong convection is progged to develop late this afternoon and evening across KS/NE/IA once again in response, eventually growing upscale into another eastward- propagating linear MCS. Similarly to this morning, CAM runs continue to depict a similar weakening of this system as it reaches the Mississippi River and spreads into WI/IL early Tuesday morning with associated relatively low severe potential. The lingering MCS cold pool footprint and residual cloudiness will likely delay destabilization into midday Tuesday, though additional storm development appears possible across the southeast half of the forecast area Tuesday afternoon/evening as the cold front finally pushes through the forecast area. Stronger mid-level flow on the southeastern periphery of the aforementioned short wave will likely support enough storm organization for a hail/wind threat during this time. Following the cold front, surface high pressure is progged to build east into the western Great Lakes region Wednesday and Thursday. Dry, but breezy and cooler weather is expected both days, with temps mainly in the 60s, but only in the 50s near Lake Michigan with northeast-east flow off the lake. Nighttime lows in the 40s are expected. The high then drifts off to the east Thursday night, with the upper level pattern favoring a series of mid-level disturbances tracking through the area Friday into the weekend. This will support milder temperatures, but also some occasional shower/thunderstorm chances into the holiday weekend. Ratzer && .AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 109 PM CDT Mon May 18 2026 Wind field has been substantially altered by storms this morning, but will revert back to a south-southwest direction early this afternoon. Pressure gradient is baggier in the wake of the storms than originally forecast, so gustiness of the winds may be slower to develop today than indicated in the TAFs. Showers and storms that develop over the central Plains today will move east and likely reach northern Illinois in a quickly decaying state late tonight/early Tuesday morning. Confidence is low in whether this activity will reach the terminals, so opted to just hang onto a PROB30 in the TAFs. Finally, confidence in winds Tuesday is on the lower end of the spectrum. There is a chance wind fields could be altered by diminishing storms, which could play havoc on directions and speeds. However, if wind fields aren't significantly altered, then winds will likely be even stronger than indicated in the TAFs. - Izzi && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago