248 FXUS63 KLOT 312316 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 616 PM CDT Sat May 31 2025 .KEY MESSAGES... - Wildfire smoke from Canadian fires will continue to filter over the area through the weekend. Most of this smoke should remain aloft and result in hazy skies. - Above average temperatures expected early next week, with warmth right up to the lakefront. - Potentially wetter pattern setting up midweek with one or more rounds of showers/storms possible Tues night through Thursday. && .DISCUSSION... Issued at 200 PM CDT Sat May 31 2025 Through Sunday Night: A long wave trough over eastern Canada keep northerly flow over northeastern Illinois and northwestern Indiana this evening. There is a short wave embedded in the longer wave passing south over Iowa and Missouri later this evening, but being so far removed from the better forcing, no precip is expected. There is a small ribbon of mid layer moisture draped from a Rockford to Pontiac line allowing for some partly cloudy skies. But those clouds are expected to drift west away from the area tonight. While most observations are recording "sky: clear", one look outside (or via true color satellite imagery) and there is a bit of a haze in the skies as a result of Canadian wildfire smoke riding the northerly flow over the area. Not only was sky cover kept up in the forecast due to the hazy conditions, the hazy conditions were extended into Monday morning as models are suggesting the thickest plume aloft is not expected to drift over the area until a little later than originally anticipated. The current expectation is for the smoke to remain aloft, but trends will be monitored closely. An upper level ridge will slowly move eastward toward the area on Sunday. Temperatures are expected to be mid to upper 60s closer to the lake and mid to upper 70s farther inland under "sunny" skies (again, not counting the haze). Although it should be noted that there is slightly lower confidence in the temperature forecast given the uncertainty in the amount of smoke aloft which may limit heating. DK Monday through Saturday: Mid and upper level ridge is progged to build eastward across the Mississippi Valley and Great Lakes region Monday into Tuesday. Southerly winds and warm air advection should set the stage for a couple of days with very warm temperatures. While it looks like Monday should be largely cloud-free, there is a great deal of uncertainty regarding how much recycled upper level smoke could be around Monday. If there is an upper level layer of smoke it would likely temper insolation some and result in temps a bit cooler than currently forecast. By Tuesday, any smoke should be safely blown well to our north and east, but cloudiness will probably be on the increase in advance of the next system. Despite some increase in cloud cover, strong southerly winds should still allow for highs to climb well into the 80s to perhaps some low 90s if clouds are a bit slower to arrive. Upper trough and associated surface cold front are progged to move across the are Tuesday night into early Wednesday with chances for showers and thunderstorms. Moisture return from the Gulf will be somewhat stunted by sfc ridging being slow to move off to the east and allow for better moisture return. This could temper the severe threat some, but at this distance can`t argue with likely pops offered up by the NBM given the respectable forcing. There remains spread in the medium range guidance later Wednesday through Thursday regarding how far south this boundary settles. The 12z operational runs of the GFS and ECMWF both eject out an upper low from the southwest with this shearing out shortwave riding the west-southwesterly flow into the Midwest, similar to the 00z runs. There is significant spread in both models` ensemble suites in how this upper low ejection is handled, so confidence is still pretty low. If this shearing out upper low were to eject out in and drag that boundary back north, there would likely be another round of showers and thunderstorms in the later Wed night or Thursday time frame. Given the large spread in the ensembles, didn`t see any compelling reasons to stray from NBM pops which do have high end chance/low end likely pops late Wed night or Thursday. A trend toward cooler, more seasonable temperatures is expected during the second half of the upcoming work week. Izzi/DK && .AVIATION /00Z TAFS THROUGH 06Z SUNDAY/... Issued at 616 PM CDT Sat May 31 2025 No major forecast concerns are expected at the terminals as a weak surface high will remain overhead. The ongoing 10-12 kt northeast winds will ease over the next 1-2 hours resulting in light and variable winds overnight. Directions will resume from a east-northeast direction at the Chicago terminals and GYY Sunday afternoon behind a lake breeze with speeds increasing slightly into the 6-8 kt range. Elsewhere, winds will remain light (around 5 kts) out of the northwest. Otherwise, expect VFR conditions to prevail through the period with hazy skies courtesy of Canadian wildfire smoke but no surface impacts expected. Yack && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago