Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
152 FXUS63 KMKX 092353 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 653 PM CDT Sun Aug 9 2026 .KEY MESSAGES... - Thunderstorm chances again this evening/tonight for southeastern WI toward the WI/IL border. Stronger storm or two cannot be ruled out. - Any storms this evening/tonight will be capable of heavy rain and localized flooding, especially where storms repeatedly track. - Periodic chances for showers and thunderstorms are possible through the first half of the week. && .UPDATE... Issued 650 PM CDT Sun Aug 9 2026 Currently seeing a narrow line of storms moving eastward across southeastern WI, but as they move off of the instability gradient, then remain relatively on the weaker side with the main hazard being a brief downpour and lightning. This activity will linger for another hour or two before pushing out over Lake Michigan. There remains a possibility for additional showers and storms to develop late this evening/overnight along the lingering instability gradient. The latest trends have this area either just along the WI/IL border and south thanks to the more robust daytime convection. Nevertheless, some CAMs, such as a few of the more recent runs of the HRRR, do try and sneak that instability gradient just north into far south-central and southeastern WI, which could support additional thunderstorm development capable of producing heavy rainfall and localized flooding if this scenario materializes. However, the more favorable environment and upper-level support favors this activity to develop south into IL/IN areas rather than WI, but bears watching. Otherwise, given the light winds and ample low level moisture, expect widespread fog to develop across southern WI overnight into early Monday morning. Low-lying areas may see pockets of lower visibility through daybreak. Wagner && .SHORT TERM... Issued 200 PM CDT Sun Aug 9 2026 Tonight through Monday night: There will be some evening storm potential but there remains higher uncertainty given the the day time convection and uncertainty in how its progression will affect where the boundary sets up tonight in addition to the questions regarding recovery. The warm front will still remain well to the north and bring some convection to northern WI where we will be focused on the placement of the remnant boundary from daytime storms, but the return flow should allow for a window of destabilization. In addition effective bulk shear should be around 40-50 kts. Thus the environment is capable of bringing severe storms provided we get storms. In addition, where this boundary sets up may also very well set up a significant heavy rain scenario given PWATs around 2 in and largely west to east propagation. Fortunately, corfidi vectors are a bit more progressive in the latest model runs. Wherever this sets up though we should expect heavy rain and potential for flooding. Latest models have generally trended things further south with development with far southeast WI having the greatest risk for evening storms. Outside of light pockets of rain from WAA overnight into Monday we will carry limited precip chances as the warm front sags south out the area tonight. Most models have the front stalling just south of the WI/IL border with Monday afternoon and evening activity largely staying south of the CWA though if this front is even slightly further north that would put us in a zone of increased storm potential. Given plenty of instability over 2000 J/kg and effective bulk shear in the 40-55kt range there will be potential for severe storms though forcing may not be strong enough from just the front as several CAMs struggle to produce convection at all Monday afternoon/evening. This will be a period to watch but chances will be limited as there are multiple pieces of model output that limited chances for storms generally in addition to the location of any initiation likely being focused south. We will be mentoring forcing and potential initiation location closely over the next 12-24 hours. Kuroski && .LONG TERM... Issued 200 PM CDT Sun Aug 9 2026 Tuesday through Sunday: Early Tuesday morning a shortwave will be sliding through southern MN into southern WI and/or northern IL into the day with an instability gradient likely set up WNW to ESE in that same general vicinity. This will likely be elevated given the morning timing but we cannot rule out something surface based and given deep layer shear around 40+ kts severe storms could be possible through the early afternoon as this feature tracks through the region. There is naturally quite a bit of uncertainty with this given some much activity through Monday that may affect Tuesday potential but the setup is favorable for strong to severe storms with heavy rain. We do get a sneak peek at some the end of the time range of CAMs for this period and a there are several that develop organized convection tracking for WI/IL border so that will be something to watch. Beyond Tuesday uncertainty increases significantly though the pattern remains the same with ridge to the west and trough to the east that the upper levels indicate several shortwaves swinging through throughout the remainder of the week. In addition, the instability gradient will likely be in the region throughout the week with decently strong shear. Cannot rule out strong to severe storms at various points the rest of the week Kuroski && .AVIATION... Issued 650 PM CDT Sun Aug 9 2026 A narrow line of weakening showers and storms will impact far southeastern terminals through 01z before diminishing/moving out over Lake Michigan. Then will be keeping an eye on the potential for additional develop later this evening and overnight for terminals along and just north of the WI/IL border. The more favorable environments remains down in IL to support this activity, however cannot complete rule out seeing it shift just north of the WI border. If this case materializes, then terminals such as JVL or ENW could see a period of heavy rainfall, reduced visibility, along with a few stronger gusts mainly between 03-07z. Otherwise, much of southern WI terminals will see lighter winds paired with ample low level moisture to support fog development and lowering ceilings. Expect widespread MVFR levels to accompany these conditions, with pockets of IFR and even LIFR especially for areas that saw heavier rainfall earlier in the day. Then conditions are expected to improve after daybreak as the stalled frontal boundary remains south of the area into IL and weak high pressure tries to build in through the afternoon. Wagner && .MARINE... Issued 200 PM CDT Sun Aug 9 2026 Winds will become light and mostly variable ahead of a sagging front. The front will move southward down the lake into Monday, leading to light northerly winds through the morning on Monday and light and variable winds Monday afternoon and evening. Light and variable winds then persist into Tuesday as high pressure of 30.0 inches remains in place north of a frontal boundary parked over the Corn Belt. Otherwise an unsettled weather pattern has set up over the Upper Great Lakes this week where weak waves of low pressure will cross the region and produce rounds of thunderstorms at times primarily a risk for the south half. The first round of weakening storms should arrive late morning and early afternoon, and additional storms are possible there Sunday night and beyond. Kuroski && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, X, and YouTube at: www.facebook.com/NWSMilwaukee www.x.com/NWSMilwaukee www.youtube.com/NWSMilwaukee