Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
404 FXUS63 KMKX 190240 AAA AFDMKX Area Forecast Discussion...UPDATED National Weather Service Milwaukee/Sullivan WI 940 PM CDT Fri Jul 18 2025 .KEY MESSAGES... - Scattered showers and thunderstorms (40 to 60 percent chance) are forecast to move southeast into south central Wisconsin early Saturday morning and exit southeast Wisconsin by midday. Damaging winds are possible with stronger storms, along with some hail. There is uncertainty with how much in the way of showers and storms the area will see during this time. - 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. && .UPDATE... Issued 940 PM CDT Fri Jul 18 2025 Showers and thunderstorms have developed over central to west central Minnesota, near the cold front and the developing southwesterly low level jet. CAMs have generally been trending with the northern portions of this convection moving east along the developing warm front in northern Wisconsin overnight into Saturday morning. They have the rest of the convection shifting southeastward and either missing the area to the southwest or having scattered convection move through the area during the early to middle morning hours on Saturday. This generally follows the instability gradient from Minnesota into eastern Iowa and northern Illinois. Recent CAM runs have been back and forth with the areal extent of the convection, so uncertainty remains fairly large with this aspect of the thunderstorm potential. CAMs have slowed a bit more with the timing of these storms, with the main window appearing to be in the 6 AM to Noon CDT time period through the area. For now, will maintain the current expectations for scattered storms to move through the area in the early to middle morning hours on Saturday. There is enough elevated CAPE and deep layer bulk shear for strong winds to occur with the storms, and perhaps some hail and brief heavy rainfall. The potential second round of more isolated to scattered showers and storms with the cold frontal passage Saturday afternoon lingers as well. However, the later timing of the exiting storms may leave cloud debris around long enough to limit sunshine and instability for this next potential round. This will be the key for additional storms Saturday afternoon. Again, if the storms develop, there is the potential for strong winds and some hail with the stronger storms. Wood && .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 940 PM CDT Fri Jul 18 2025 There is the potential for scattered showers and storms shifting southeastward and either missing the area to the southwest or moving through the area during the 11Z to 17Z period on Saturday. Uncertainty remains fairly large with this aspect of the thunderstorm potential, so keep up with the forecast. If storms move through, strong winds and some hail are possible. The potential second round of more isolated to scattered showers and storms with the cold frontal passage Saturday afternoon lingers as well. This would generally be in the 19Z Saturday to 00Z Sunday period. However, the later timing of the exiting storms may leave clouds around long enough to limit sunshine. This will be the key for additional storms Saturday afternoon. Again, if the storms develop, there is the potential for strong winds and some hail with the stronger storms. Otherwise, light south winds overnight will become southwest on Saturday, then west to northwest behind the cold front during the afternoon and northwest to northeast Saturday night. Middle to high clouds should move into the area overnight into Saturday morning, with some ceilings down to around 2500 to 3000 feet AGL at times if any thunderstorms develop and move through. May see brief visibility reductions to 2 to 4 miles with storms as well. There is some potential for lower ceilings down to or below 2000 feet AGL later Saturday evening and night to develop. Wood && .MARINE... Issued 940 PM CDT Fri Jul 18 2025 High pressure around 30.1 inches over Lake Erie will continue to move east tonight, as low pressure around 29.8 inches develops in the lee of the Colorado Rockies. A warm front will develop across northern Wisconsin and the Upper Peninsula of Michigan overnight, bringing showers and thunderstorms to the northern half of the lake. Additional thunderstorm development is possible across the southern half of the lake into Saturday morning. Light south to southeast winds will become south by Saturday morning. Winds become southwesterly as the showers and storms end by midday Saturday, then become northerly behind a cold front Saturday afternoon and evening. A few thunderstorms are possible along this front. High pressure around 30.0 inches will settle back into the region on Sunday, slowly departing into Monday and shifting winds to easterly. A low pressure trough around 29.8 inches will cross the Upper Midwest on Tuesday, bringing southeasterly winds. MH/Wood && .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