682 FXUS63 KLOT 011117 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 617 AM CDT Sun Jun 1 2025 .KEY MESSAGES... - Wildfire smoke from Canadian fires will continue to filter over the area through Monday. Most of this smoke should remain aloft and result in hazy skies, though some smoke may reach the surface Monday afternoon. - Above average temperatures expected early next week, with warmth right up to the lakefront. - Period of showers and storms is likely late Tuesday through early Wednesday time frame. - Much lower confidence, but a second round of showers and t-storms is possible late Wednesday into Thursday, especially southeastern CWA. && .DISCUSSION... Issued at 310 AM CDT Sun Jun 1 2025 Through Monday: Surface high pressure will remain centered over the forecast area through this evening before shifting to the southeast on Monday. Light north winds are favored today, with an easterly shift with a lake breeze across northeast Illinois and northwest Indiana this afternoon. Light southeast winds will then veer southwest and increase on Monday. The main impact on sensible weather will remain the veil of Canadian wildfire smoke filtering over the region. The smoke should remain aloft through at least Monday morning. However, higher concentrations will begin to advect eastward with the veering flow through the day Monday. Guidance hints that diurnal mixing may begin to bring down some of the smoke to the surface in the afternoon, so will need to follow trends and introduce at lease some mention of smoke in the forecast with subsequent updates. Hazy skies will persist during what would normally be a period with little cloud cover. Additionally, the persistent smoke should slightly temper high temps today and Monday, so have lowered values by a degree or two areawide both days. Kluber Monday Night through Saturday: Tuesday should be windy and very warm ahead of the approaching upper trough and associated sfc cold front. Can`t rule out some smoke linger into Tuesday, which could keep high temps a bit cooler. Did shave a few degrees off of NBM temps Tuesday in our western CWA, where cloud cover and maybe some late afternoon showers and storms could make reaching upper 80s a challenge. Elsewhere, stuck with upper 80s offered up by the NBM, but lower than average confidence given the potential for cloud cover and or smoke keeping it a bit cooler. Showers and thunderstorms should overspread the CWA Tuesday night. NAM instability looks overdone due to its moist boundary layer bias. Weak mid level lapse rates and stunted heating of the boundary layer suggest that instability in our area should be pretty weak, likely only peaking around 500 J/kg over our western CWA Tuesday evening. Cannot totally rule out a low end severe risk Tue evening in our western CWA, but chances look pretty low/conditional. Convection should generally be in a weakening phase overnight as it moves in progressively less unstable air mass over eastern IL and northwest IN. Cut off low over the dessert southwest is still progged to eject out and ride the west-southwesterly flow in the Midwest or Lower Ohio Valley region Wednesday night into Thursday. Still a lot of spread in guidance regarding how far south of our area the boundary will get before stalling out and possibly retreating north some in advance of the shearing out shortwave. Operational GFS has trended toward a more southerly solution with the stalling out of the front and would suggest our area largely dry out late Tue night/early Wed morning and stay dry the rest of the week. The 00z ECMWF still stalls the boundary closer to our CWA, before lifting it north slightly with more widespread shower and thunderstorm activity. With considerable spread in the ensembles, confidence remains on the lower end of the spectrum. Given the low confidence, made no adjustments to NBM pops, which do favor our southern CWA with higher pops, which looks reasonable. Drier conditions are expected Friday and Saturday with cooler, more seasonable temperatures and winds off the lake keeping temps cooler lakeside. - Izzi && .AVIATION /12Z TAFS THROUGH 18Z MONDAY/... Issued at 617 AM CDT Sun Jun 1 2025 - Gradually lowering smoke layer expected through the TAF cycle, though not expecting any sfc VSBY restrictions through at least tonight. Other than a lake breeze this afternoon, expect light winds through early Monday morning. VFR conditions are expected through tonight. A smoke layer aloft is forecast to gradually lower through the next 24-30 hours, possibly lowering to an MVFR CIG (of smoke) by later Monday morning. As mixing deepens, some smoke could mix to the surface and result in some minor (likely VFR) obscuration to visibility late Monday morning. - Izzi && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago