870 FXUS63 KLOT 140802 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 302 AM CDT Sat Jun 14 2025 .KEY MESSAGES... - Chance for showers this morning, mainly southeast of a Livingston County to Jasper County line - Temperatures will increase this weekend and into next week, accompanied by increasing shower/storm chances by midweek. - Severe weather is possible next week, particularly Wednesday, with multiple rounds of thunderstorms possible Monday through Wednesday night. && .DISCUSSION... Issued at 302 AM CDT Sat Jun 14 2025 Through Sunday: KLOT radar is showing diminishing shower coverage over the southeastern portions of the forecast area. These showers are situated along and just north of a quasi-stationary boundary from St. Louis, MO to Lafayette, IN. This boundary is associated with an upper level low sitting over eastern Missouri/southwestern Illinois. Over the next 6 to 12 hours, this low is expected to weaken as it slowly moves east over southern Illinois. Its gradual movement will help nudge the surface boundary southeast of the forecast area through the morning. Showers are expected to linger through the morning and into the early afternoon mainly along and southeast of a Livingston County to Jasper County line. Weak forcing should help keep rain rates low, though with over two inches of precipitable water there remains a chance for a downpour to focus over an area that received rainfall last night which result in ponding in flood prone areas. Lastly, model soundings do show an a sliver of instability late this morning and into the afternoon. However, those soundings are fairly capped and not expected to break that cap until the showers move southeast of the area. Perhaps an isolated thunderstorm or two develops, but the better instability will be to the south along the boundary as it slinks away from the forecast area through the day. An upper level high will strengthen over New Mexico and build a ridge into the Plains today. Drier air and increasing subsidence moving into the forecast area ahead of the ridge is expected to reduce cloud cover this afternoon, at least to the west. Temperature are expected to reach he lower 80s for areas west of the Fox Valley which should receive more sunshine. However, as cloud cover is expected to linger for much of the day closer to the lake and over northwestern Indiana, that (and northeast winds over the lake) should help cap high temperatures for those areas in the mid to upper 70s. Cloud cover will continue to erode tonight as dry conditions prevail and low temperatures in the upper 50s/low 60s are expected. As a weak upper level pattern remains, most of Sunday should stay dry. Clearer skies should allow for more of the forecast area to warm up solidly into the 80s, though northeast winds off of the lake will help keep the lake shoreline in the 70s. Models keep suggesting a very weak upper level short wave that develops and moves down the ridge from southeastern Minnesota to southern Wisconsin. Combine that with diurnal heating and there is a slight (less than 25 percent) chance for some showers and thunderstorms on Sunday afternoon in northwest Illinois and along the Wisconsin stateline. There is better confidence for the showers and storms to be northwest of the Rockford Metro area, but whether or not it materializes will depend on the movement of that wave and how close to the forecast area it gets before the sunsets and a less favorable time of day for storms. DK Sunday Night through Friday: Guidance remains in good agreement in depicting a more zonal flow pattern in the mid-upper levels to start next week. Surface high pressure stretching from the Great Lakes through New England drifts slowly to the east Sunday night into Monday, while warm, moist southerly return flow develops off of the western Gulf into the Plains and upper Midwest/Mississippi Valley. Models depict several low-amplitude short wave disturbances tracking eastward across the region along the southern periphery of stronger jet winds, which should modulate diurnal thunderstorm initiation across the upper Midwest and development of a few MCSs, which could affect our forecast area. Various models show quite a bit of differences in details with these low-amplitude waves, not surprisingly, leading to fairly low confidence in exact timing and placement of them and any organized convective complexes they produce. Global ensembles continue to indicate a more amplified mid- level short wave tracking across the central and northern Rockies and onto the Plains late Tuesday and into the Midwest Wednesday/Wednesday night. While some differences remain with the timing and strength of this feature, the general trends support an area of surface low pressure lifting northeast across the upper Midwest Wednesday with attendant synoptic increases in low-level warm sector theta-E, instability and vertical wind profiles. This pattern appears supportive of heightened severe thunderstorm potential within the region on Wednesday, which will continue to be monitored for a possible severe weather threat in or close to the WFO LOT forecast area. Ridging in the wake of the more amplified mid-week system may ease the periodic shower and thunderstorm threat for at least a portion of the latter half of the week, though there is some indication that the main upper ridge axis will set up to our west keeping us along the southern periphery of additional shower/thunderstorm threats across the upper Midwest. Temperatures are forecast to warm into the mid-upper 80s early next week, with 90 not out of reach especially Tuesday and Wednesday. This will be dependent on thunderstorm trends and affects of any outflow boundaries, however, lending somewhat lower confidence to current forecast highs. Humidity levels will be on the rise through mid-week as well. Ratzer && .AVIATION /06Z TAFS THROUGH 12Z SUNDAY/... Issued at 1230 AM CDT Sat Jun 14 2025 Key Aviation Forecast Messages for the 06Z TAFs: - Period of IFR ceilings likely through sunrise, improving to VFR by midday. Early morning surface map shows low pressure centered just south of KSTL, with a nearly stationary frontal boundary extending northeast along/just south of a KCMI-KDNV-KMIE line. North of this front, relatively cool, moist northeast flow was in place across the terminals. While an area of showers will remain largely south of the area this morning, a few spotty light sprinkles can`t be ruled in the KMDW/KGYY vicinity for the next few hours. Within the moist northeast flow, surface and satellite observations indicate increasing low-level cloud cover developing off of Lake Michigan into northeast IL. Model guidance strongly supports the development of IFR ceilings which may linger through sunrise before gradually improving through MVFR during the morning. VFR conditions are expected by late morning/midday. Model guidance indicates KRFD may develop a low-end MVFR ceiling of around 1000 feet toward sunrise, before also then improving to VFR later in the morning. Winds through the period are expected to be generally northeast around 10 kts, eventually becoming more light/variable later Saturday night. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago