Four Lakes Village Snow Report

885 FXUS63 KLOT 300722 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 222 AM CDT Sun Aug 30 2026 .KEY MESSAGES... - Periodic shower and storms through the early part of the week, though there will ample dry periods. - Hotter and more humid conditions build through midweek. && .DISCUSSION... Issued at 222 AM CDT Sun Aug 30 2026 As a low level jet (LLJ) increases this morning, as sampled around 40 knots just 2000 ft AGL on the KLOT VAD, it is no surprise that shower coverage is gradually expanding over northern Illinois. PoPs were increased to around 30 to 40 percent chance to match the coverage being observed. This southwest to northeast oriented LLJ is expected to pivot and become slightly more easterly oriented through the morning and be the driving force behind an increase in shower coverage. There is modest effective shear present, but CAPE values and lapse rates are not providing confidence in overall coverage of thunder. That being said, there have already been small clusters of embedded thunderstorms develop early this morning. Most thunder is expected to be isolated, but there could be an uptick in thunder coverage right around and after daybreak. Current guidance is suggesting the LLJ will gradually diminish around midday allowing the showers to eventually erode and sink southward as it falls apart. An upper level ridge, the center of which is currently analyzed over Oklahoma and Texas, keeps northern Illinois and northwest Indiana along its northern periphery through midweek. There will be plenty of dry times, but as embedded waves moves through the pattern, there will be additional periods of showers and storms. For example, RAP analysis is currently showing an upper level short wave from Rapid City, SD to around Dodge City, KS just behind ongoing storms in the Great Plains. There is an additional short wave in western Wyoming and Colorado. Models are suggesting that that both these waves are expected to ride along the top of the ridge and provide additional chances for precipitation overnight tonight (the Plains wave) and again overnight into Tuesday morning. If the ridge were to strengthen, it could force these waves (and subsequent shower/storm chances) farther north. Whether or not they maintain their current trajectory or strength remains to be seen. For now, chances for showers and storms remain in the forecast through the middle of the week. As the ridge remains over the CONUS through midweek, so does southwesterly flow at the mid-levels. This wind direction will aid in advecting in a warmer air mass to the western Great Lakes with projected 850 mb temperatures over 20C, potentially pushing 25C. Winds at the surface will also remain out of the south, gradually increasing dew points through the week back into the 70s. Hotter temperatures in the upper 80s and lower 90s are expected. This combination of hot temperatures and humid conditions are expected to increase heat indices into the mid to upper 90s by midweek, with the southwestern portion of the forecast area with a chance of exceeding 100. Chances for shower/storms through the weak lowers confidence in specific temperatures values; therefore, there was no consideration at this time for any heat hazard products (advisory/watch). Models are suggesting that the ridge could break down by the end of the work week. That will help the hottest of temperatures to cool off a bit, but it will return the upper level flow pattern to the northwest and thus bring with it additional chances for showers/storms over the weekend. DK && .AVIATION /06Z TAFS THROUGH 12Z MONDAY/... Issued at 1228 AM CDT Sun Aug 30 2026 Spotty showers are ongoing across the central ZAU airspace at press time associated with isentropic ascent being forced by a southwesterly 35-40 kt low-level jet oriented toward the Great Lakes. As the orientation of the low-level jet turns more westerly toward daybreak, the expectation is for coverage of showers to increase and peak generally in the 11 to 15Z timeframe, give or take an hour. With mid-level lapse rates gradually steepening through the night, opted to convert the inherited PROB30 groups to TEMPOs for -TSRA this morning (will note there has already been lightning in activity across southern Wisconsin early this morning). Winds overnight through mid Sunday morning should remain generally where they are right now out of the southwest at 10 to 15 kt (southeast at rural terminals). As the low-level jet starts to weaken by mid-morning, coverage of showers should correspondingly decrease. Upward mixing into the base of the decaying low-level jet should still promote southwesterly gusts increasing to 25 kt or so from mid-morning to early afternoon. A shower or two may remain in the area through early afternoon. Toward mid-afternoon a remnant MCV originating out of ongoing convection in southern Nebraska will move into the Lower Great Lakes. Suspect there will be another period of showers across the region as the MCV moves through, though am not confident the highest coverage will be over the terminals or over southern Wisconsin. For now, will simply cover the threat with a prolonged VCSH through early evening. Tonight, currently expect dry conditions with a southwesterly breeze around 10 kt (southeasterly directly at rural terminals). A few showers may develop toward daybreak Monday at the nose of another low-level jet. Will tackle that window in a later TAF package. Borchardt && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago