


Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
058 FXUS63 KMKX 182036 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 336 PM CDT Fri Jul 18 2025 .KEY MESSAGES... - An area of showers and thunderstorms will likely (50 to 70 percent chance) roll into south central WI early Saturday morning and exit southeast WI by midday. Gusty winds are possible with stronger storms. - Additional showers and thunderstorms are possible Saturday afternoon along a cold front. Storms may produce damaging winds and hail. - Chances for storms develop on and off early through late next week, but timing and intensity remains uncertain at this time. - Heat builds back into the region with highs in the upper 80s to lower 90s Tuesday into the end of the week. && .SHORT TERM... Issued 336 PM CDT Fri Jul 18 2025 Tonight through Saturday night: Light winds and lows in the mid to upper 60s through midnight, as high pressure exits to the east and winds kick southeasterly and bring a return to warm, moist conditions. Exiting 200 mb jet will continue to produce showers and potentially thunderstorms across northern Minnesota and northern Wisconsin into tonight. Warm frontogenesis developing across the same region will bring additional lift and allow storms to progress southeastward through the overnight hours as the front sags southward. A second area of storms will develop early tonight across northern Nebraska at the apex of the 850 mb LLJ, following bulk shear vectors east-southeastward through Iowa overnight. Placement and extent of these features remain uncertain, and likely will continue to be uncertain until they complete their development tonight. Two main solutions arise, with the first, more intense scenario indicating that plenty of moisture and elevated instability indicated by MUCAPE of 1000 to 1500 J/kg will only require a trigger to fire off storms across southern Wisconsin, allowing the two storm systems to connect through southern Wisconsin due to phasing of their respective shortwaves. this would allow for lightning and locally heavy rain, with potential south of I-94 to produce strong to severe storms as the southern MCS taps into better instability along the Wisconsin/Illinois border and intensifies into the Saturday morning timeframe. The second, less intense scenario depicts only isolated to scattered storms across southern Wisconsin with each MCS remaining separated throughout the overnight hours into Saturday morning. Regardless of solution, morning convection ends by noon at the latest. Going into Saturday afternoon, a cold front from a weak low pressure system traversing northern Wisconsin into Michigan will drag across southern Wisconsin. Due to the uncertainties lingering for overnight convection, uncertainties continue into Saturday afternoon. If phasing occurs and more widespread convection develops across southern Wisconsin Saturday morning, overcast skies will likely linger and prevent diurnal heating from destabilizing the atmosphere. This would allow for weak, pulse- type thunderstorms along the front. However, if no phasing occurs overnight and conditions remain relatively dry, clearing skies and a redevelopment of convection is possible. This would lead to stronger storms along the front, capable of producing gusty winds and small hail. All storms will exit into Lake Michigan going into late Saturday evening. CAMs depict potential for thunderstorm development along the Wisconsin/Illinois border once again Sunday night along the now- stationary front, bringing slight chances for precipitation across far southern Wisconsin (20-30 percent). Lows in the lower 60s. MH && .LONG TERM... Issued 336 PM CDT Fri Jul 18 2025 Sunday through Friday: Stationary front remains just south of the Wisconsin border through Sunday and into Monday as high pressure settles into the Great Lakes region once again. On and off chances for showers and storms are expected across far southern Wisconsin, but chances remain low (15-30 percent). Low pressure develops and pushes eastward into the Upper Midwest on Tuesday, bringing stiff southerly winds and heat back to southern Wisconsin through the day (highs in the mid to upper 80s). Warm frontal feature will lift into the region Tuesday night, with potential for storms along it (30-50 percent chance). Heat continues into Wednesday, with highs in the upper 80s to lower 90s within the warm sector. Timing is in question for the low`s progression eastward, but best chances for thunderstorms in the evening to overnight (40-50 percent chance). Ridging continues to build across the southern U.S. Wednesday through Friday, putting southern Wisconsin firmly into the ridge riding MCS setup. Therefore, NBM PoPs of 20-40 percent linger through the rest of the week. Still, expecting future refinements to the forecast to nail down specific timeframes of interest with future modeling. Regardless of exact timing of storms, expect heat and humidity to continue into Friday. MH && .AVIATION... Issued 336 PM CDT Fri Jul 18 2025 Scattered deck around 2500 ft near Lake Michigan will slowly dissipate this evening, while scattered deck around 3500 to 4500 ft does the same inland. Southeasterly winds are expected to dominate, but will remain weak and sometimes variable through this afternoon and evening. Late tonight into early Saturday morning, a thunderstorm complex will develop across northern Wisconsin, and an additional thunderstorm complex will develop across Iowa. A line of scattered thunderstorms may develop across southern Wisconsin during this time frame, bringing briefly gusty winds, reduced visibilites, and MVFR cloud decks, especially to southern terminals. Winds shift to southwesterly behind this activity. Storms will exit to the southeast by noon on Saturday, with isolated storms possible again along a cold front Saturday afternoon. More scattered, stronger storms are possible Saturday afternoon if Saturday morning convection does not develop. Winds shift to become northwesterly behind the cold front. MH && .MARINE... Issued 336 PM CDT Fri Jul 18 2025 High pressure over the Great Lakes region will slowly exit to the east tonight as low pressure develops in the lee of the Colorado Rockies. A warm front will develop across northern Wisconsin and the Upper Peninsula overnight, bringing thunderstorms to the northern half of the lake into the late overnight hours. Additional thunderstorm development is expected across the southern half into Saturday morning. Winds become southwesterly as these storms end midday Saturday, then become northerly behind a cold front Saturday afternoon. Isolated thunderstorms are possible along this front. High pressure will settle back into the region on Sunday, slowly departing into Monday and shifting winds to easterly. A low pressure trough will cross the Upper Midwest on Tuesday, bringing southeasterly winds. MH && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee