NWS Milwaukee Forecast Discussion
841 FXUS63 KMKX 090036 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 736 PM CDT Sat Aug 8 2026 .KEY MESSAGES... - Dry and pleasant today with highs in the low 80s. - Thunderstorm chances return Sunday. There is the potential for a late morning to afternoon round, and then an evening and overnight round. Strong to severe storms will be possible. Uncertainty remains regarding exact timing of the rounds and positioning. - Any storms on Sunday will be capable of heavy rain. Localized flooding will be possible, especially where storms repeatedly track through the day. - Multiple rounds of rain and thunderstorms are possible through the work week. && .UPDATE... Issued 730 PM CDT Sat Aug 8 2026 High pressure is moving east through IA and northern IL this evening. This will keep conditions quiet through the rest of the evening into early tonight. As the night wears on, the LLJ is expected to nose into southern Wisconsin with southwest winds and WAA kicking in during the early morning hours. With bulk shear around 40 kts, good moisture returns and a shortwave trough providing lift, the one question for strong to severe storms continues to be the presence of any instability. Instability or the lack of it will be a fact in if storms roll through the entire area or are on a dying trend as they push east. Timing is still a bit uncertain on when storms are expected to develop in the Dakotas and Minnesota. The further west they develop then the later into the morning these storms will move through. Meso models like the ARW and FV3 look to have an early arrival time around 7 AM while the HRRR and NAM nest delay storms a couple hours until around 10 AM. This difference in timing and strength will then impact storms later in the afternoon/evening with a second shortwave trough. The second round of storms still has many questions yet to answer in how this plays out. Similar to a game of cards, we need to see how the first hand is dealt. No major changes yet here for the forecast in the short term. Hoping the 00Z guidance will shed some more light on the situation. Patterson && .SHORT TERM... Issued 1229 PM CDT Sat Aug 8 2026 Tonight and Monday night: A very unsettled pattern arrives late tonight as high pressure pushes out ahead of an approaching low from the west. This system will carry some punch with strong WAA in the low to mid levels and a fairly substantial LLJ and a decent shortwave. Given some sun ahead of storm development we should see at least modest instability just ahead of the impending precip, and CAMs backup the idea that some storm development should be expected with the best chances further south of I-94 with the better instability. How long storms persist is in question further north given less instability but this part of the system should be fairly progressive with storm activity pushing out by the late morning to early afternoon. Cannot rule out severe storms with this either given deep layer shear increasing to 50-60kts. Altogether there is quiet a bit of uncertainty with morning convection as the shear may lag behind the convection a bit which would nix severe risk for the most part in addition to the uncertainty with instability and the likelihood that storms would most likely be elevated. There may be a brief quiet spell in the early to mid afternoon for a period of recovery before additional ripples in the upper levels and the continued LLJ and the front all playing a role. A secondary firing of convection appears likely for somewhere but exactly where that occurs is still in question. Trends in models have definitely shifted things a tad south more toward the WI-IL border but this will be something to monitor as it will determine how impactful this will be. Where these storms fire will present an escalating heavy rain and flash flooding risk given PWATs around 2 inches, west to east propagation and variable corfidi vectors which is indicative of training convection with back building. Some storms may become severe as well given plenty of instability with deep layer shear around 40-50kts, but the best chances will be on the south side of wherever storms set up given the better continuous inflow. CAMs are a bit all over the place with this convection with uncertainty on where this sets up and for how long, but these same models are also suggestive of things clearing out late Sunday night. Into Monday uncertainty grows further but trends have suggested that the front will sag further south perhaps taking southern WI out of the primary risks for precipitation and storms. There remains a chance that the front remains over southern WI instead of pushing south which would keep the door open for severe and flooding concerns so we will be closely monitoring the progression of the front on Sunday into Monday. Kuroski && .LONG TERM... Issued 1229 PM CDT Sat Aug 8 2026 Tuesday through Saturday: As we remain stuck in this pattern with low pressure over Hudson Bay and high pressure over the southern U.S. with weak shortwaves in between, the forecast for southern WI will continue to be uncertain in terms of storm chances and timing. Right now, it looks like the main 850mb frontal boundary will end up stationed in northern IL rather than southern WI, but there is still room for that boundary to wiggle northward at times. That frontal boundary will be the focus for storm generation from Tuesday through Thursday morning. So Monday night/Tuesday morning storms will once again depend on the Monday storm movement and where the outflow and effective front land. It will also depend on where the low level jet develops Mon nt (and the position of the nose of the LLJ). It will also depend on if there is a shortwave tracking across that location at the same time in order to help initiate more organized convection. Therefore, we have highest chances (55-65%) for storms in the southern tier of counties Tuesday morning and lower chances (30-45%) in the afternoon. The afternoon scenario would be for additional storms firing along the stalled outflow boundary (again, depends on where the morning convection takes it). Wednesday storm chances are even less certain, but trending downward. For Thursday through the next weekend, the GFS and ECMWF ensembles are showing a 500mb height anomoly over the Great Lakes (an upper trough) which could cause a round or two of storms in southern WI with the associated frontal passage. That frontal passage could move through southern WI as early as Wednesday night or as late as Thursday night. While the ECWMF ensemble suggests that the upper low is progressive and quickly brings ridging into southern WI by Saturday 8/15, the GFS Ensemble forecasts that this upper low will stall over the Northeast through at least the first half of the following week. Cronce && .AVIATION... Issued 730 PM CDT Sat Aug 8 2026 VFR conditions are expected into early this morning then conditions are expected to fall to MVFR to IFR. The mostly clear skies this evening will remain into the early morning hours. Rain and thunderstorms are expected to move through southern Wisconsin during the morning hours and exit to the east late morning/early afternoon. Heavy rain will be possible with any storms which could drop visibilities to 1-3 SM or less for a brief period of time. A few stronger storms may be possible with wind being the primary concern. Can`t rule out any small hail. Ceilings are expected to be around 2-6 kft with the storms. Additional storms will be possible in the late afternoon/evening. There is uncertainty in the strength of the second round of storms due to how long the morning round lasts. If the morning round is weak and fast then there will be a chance for strong to severe storms again in the evening. Heavy rain, flooding and strong winds will be the main concerns. Visibilities and ceilings expectations will be very similar to the morning round. VFR conditions may briefing return after the rain ends, but low stratus and patchy fog may develop late Sunday night. Any fog that develops late Sunday into early Monday could drop visibilites to 2-4 SM. Light west to southwest winds this evening will stay southwesterly and increase slightly during the early morning hours. Breezy south winds will move in during the late morning/afternoon outside of any rain/storms. Light and variable winds are expected Sunday night into Monday morning. Patterson && .MARINE... Issued 1229 PM CDT Sat Aug 8 2026 Low pressure of 29.5 inches over the Hudson Bay has carried its cold front across the lake with west to northwest winds behind the front this morning that will quickly return to southerly by this evening ahead of the next approaching low pressure system. An unsettled weather pattern will set up over the Upper Great Lakes next week where weak waves of low pressure will cross the region and produce rounds of thunderstorms at times. 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