Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
822 FXUS63 KMKX 172045 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 345 PM CDT Tue Jun 17 2025 .KEY MESSAGES... - Scattered thunderstorms late this afternoon and early evening mainly along and south of a line from Madison to Milwaukee along a weak stationary front. Additional showers and scattered storms will then develop over all of srn WI late tnt. - Widespread showers and scattered storms on Wednesday with heavy rainfall at times especially for southeast WI. Urban and small stream flooding will be possible. - Hot and humid conditions are looking more likely for the weekend into early next week. Maximum heat index values around 100 degrees are forecast each day. && .SHORT TERM... Issued 345 PM CDT Tue Jun 17 2025 Tonight through Wednesday night: A weakening cold front north of Madison and Milwaukee will stall near the IL border by early evening. MLCAPE will rise to 1500 J/KG with little to no capping, while the CAMs do initiate scattered convection along the front. Wind shear is weak, but a few strong pulse storms will be possible given the respectable CAPE values and some mid to upper level dry air and 6.5-7.0 C/km lapse rates contributing to downburst potential. Late this evening into the overnight, showers and storms will continue to develop from south to north across S WI as a mid level shortwave trough, currently over IA and another over ern NE, drifts newd into se WI, while a more organized shortwave trough moves into IA and nrn MO by 12Z Wed. The storms will become more elevated with only marginal CAPE present for this later activity. Storm motion will be swly around 15 kts late this afternoon and evening within PWs of 1.50 inches, so heavy rainfall and urban and small stream flooding will be possible. The main shortwave trough coming out of nrn MO and IA Wed AM will track across srn WI on Wed, possibly into Wed evening. The wave of low pressure is now depicted to track across nrn IL and srn Lake MI, which will reduce the SVR storm threat but not the heavy rain and urban and small stream flooding potential. This will put se WI in the nw quadrants where low to mid level fgen and PVA will maximize with PWs of 1.5-1.8 inches. Saturated soundings and large scale lift will lead to high precipitation efficiency. Thus moderate to sometimes heavy rainfall rates are expected especially over se WI. Will focus on the potential for urban and small stream flooding. Lighter showers will then linger for Wed nt with nwly winds and weak cold advection. Gehring && .LONG TERM... Issued 345 PM CDT Tue Jun 17 2025 Thursday through Tuesday: Warm air advection is expected with south to southwest winds across the area Thursday into Friday night, as the surface warm front gradually shifts northeast through the region. It appears that the low level jet nose and more focused 850 mb warm air advection may develop scattered thunderstorms in northern and central Wisconsin Thursday afternoon and night, with this forcing slowly shifting southeast into the area Friday into Friday night. Forecast soundings are showing mean layer CAPE above 1000 to 1500 J/kg with deep layer bulk shear of 40 to 50 knots or more. Thus, there is potential for strong storms if they develop and/or move into the area during this period. PoPs are generally in the 20 to 30 percent range at this time, with some southern parts of the area dry, but may need to be brought upward in later forecasts. Warm and humid conditions will continue. Very warm and humid conditions are likely to occur Saturday into Monday, as ensembles and cluster analysis continue to support an anomalous ridge at 500 mb building over the eastern part of the country and southeast Canada. This should support highs around 90 degrees or into the lower 90s, with southwest winds negating any lake breezes. Heat index values will approach or exceed 100 degrees each day, so heat headlines may eventually be needed and messaging will need to be ramped up as we get closer to this weekend. A cold front may approach or stall into the region later Monday into Tuesday, which may bring the next chances for showers and storms. Wood && .AVIATION... Issued 345 PM CDT Tue Jun 17 2025 Sct-030-040 cumulus this afternoon with scattered storm development over far S WI late this afternoon and early evening. Additional showers and storms will then develop northward through the night followed by widespread showers and storms for Wed. MVFR Cigs will develop early Wed AM then fall mostly below 1 kft for Wed. Prevailing vsbys will range from 2-5SM due to rain and BR. Gehring && .MARINE... Issued 345 PM CDT Tue Jun 17 2025 Low pressure around 29.5 inches will move from Ontario into Quebec this evening. Its cold front extending southward over eastern Upper Michigan and Wisconsin will weaken and stall as it moves over Lake Michigan late this afternoon and evening. Another low pressure area of 29.7 inches will track from northern Missouri to southern Lake Michigan on Wednesday, followed by a weak ridge of high pressure by Thursday afternoon. Areas of fog may develop due to relatively mild and humid air over the cold waters of Lake Michigan. Expect light to modest southerly winds becoming light and variable late today and tonight as the front weakens and stalls over the lake. Variable winds are expected for Wednesday as low pressure moves across southern Lake Michigan in the afternoon. Modest north to northwest winds are then forecast in the wake of the low for Wednesday night into Thursday morning then turning westerly. Gehring && .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