NWS Milwaukee Forecast Discussion
285 FXUS63 KMKX 172036 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 336 PM CDT Sun May 17 2026 .KEY MESSAGES... - Line of storms pushing into southern WI later this evening/tonight with strong to severe storms capable of producing damaging winds possible, especially for areas along and west of I-39. - Another round of showers and storms late Monday night into Tuesday with a potential for strong to severe storms. - Cool and drier weather then returns for midweek. && .SHORT TERM... Issued 331 PM CDT Sun May 17 2026 Tonight through Monday night: Well the departing MCV was able to bring a part of the warm into southwestern WI and spur a supercell or two. However, much of the activity associated with the MCV is tracking northeast into Central WI. While the onshore easterly flow off of Lake Michigan is keeping the environment cool and sable at the surface, a few elevated storms are tapping into the elevated environment and maintaining their strength. There are hints of gravity waves in this environment that have occasionally helped these storms punch strong winds to the surface. Thus will see a gusty wind threat associated with this activity over the next hour or two as the system departs. For the afternoon/evening focus shifts toward the warm front strewn across southwestern WI through northern IL. Along and south of it we are seeing much warmer temps and dewpoints in the mid 60s along with SBCAPE +1000 J/kg. Models continue to show this boundary lifting north through the later afternoon and evening. However the cooler easterly winds may slow its northward progression for southeastern WI and limit the better environment closer to the Lake. While ingredients line up for additional development through the evening, the deep layer shear remains a limiting factor as it hangs on the lower end of the threshold (less than 40 kt). But given the trends today and strength of this warm front, would not be surprised to see thunderstorms develop along it as latest satellite supports more percolating cu field. Anything that does develop along and south of the front will be more surface based and capable of producing large hail, damaging winds, and even could not rule out a spin up or two given the 20-30 kt of low-level shear. However, storms are possible north of the front as well taping into MUCAPE 500-1000 J/kg and would be more elevated in nature capable of producing hail and occasionally punching down a stronger gust or two. Later this evening/tonight will be another potential for severe. This round will be associated with the line of storms ongoing out along the NE/SD border this afternoon. This feature is developing closer to the low and along the warm front where the better dynamics align. Most midday models continue to prog this line to ride along and south of the warm front eastward tonight tapping along into the surface based instability. This feature looks to sustain through IA/MN as a 40-50 kt LLJ builds in later this evening/tonight. The question is will this line maintain its strength as it moves into southern WI. While CAMs continue to project this line to weaken and gust out after crossing east of the Mississippi River into southern WI/northern IL after moving away from the better upper-level support, I do have a growing concern that the ongoing line of storms, which is showing signs of becoming a bowing segment may be able to maintain itself more than the models suggest at the moment as it looks to ride west to east along the surface warm front and instability gradient. Will also have the LLJ aiding it as well. At the very least think it will maintain strength into our western half of the CWA tonight, but may eventually tap into the more stable airmass pushed in from Lake Michigan further east. Nevertheless, if the line is able to continue into southern WI it will likely be a linear mode with potential for a few isolated discrete cells popping out ahead of it after around 03z timeframe and push through overnight and may linger into Monday morning, especially if things slow down further. This activity does look push through by daybreak. Otherwise, Monday is looking fairly dry, warm, and humid for the day Monday. Then looking at another opportunity for round of showers and storms later Monday evening/overnight ahead and along of a cold front. Continue to monitor Monday for severe potential as SPC has the area outlooked with a Slight risk (2 out of 5). While the cold front hold just to the west during the day, expect the upper-level trough to lift across the Upper Midwest later Monday wit mid-level dCVA, low-level WAA and frontogenesis moving through the area later Monday. Thus plenty of upper-leve support for strong to severe development. The question remains on where these ingredients line up as most models suggests convective initiation back to the west across MN/IA and have a line move into southern WI. Timing is the other concern as early evening development to the west moves into southern WI overnight not to dissimilar from tonight`s activity. So while still some uncertainty remains, still looking to agree on a late evening/ overnight line of storms across the area. Main concern will be damaging winds, especially with any bowing segments along with an embedded tornado or two. Also with some lingering instability ahead of the line could not rule out a few isolated discrete cells as well. Regardless, stay weather aware tonight and tomorrow as there remains multiple windows for storms with potential for strong to severe storms capable of hail and gusty winds as well a few tornadoes. Wagner && .LONG TERM... Issued 331 PM CDT Sun May 17 2026 Tuesday through Sunday: Heading into Tuesday morning, rain and thunderstorms are expected to continue across much of Wisconsin. The trough in the Rockies will continue to pull northeast into the Great Lakes through Tuesday with a shortwave trough also moving through the larger 500 mb flow. Guidance has the upper level jet strengthening a bit Tuesday afternoon into Wednesday evening. Meanwhile at the surface a cold front will be moving across the state and a surface low will be pulling northeast from northern Wisconsin toward western Quebec by Wednesday. Uncertainty remains on the exact timing that this cold front will move through southern Wisconsin. Timing will play a big role on the strength of any storms and associated hazards. Current model trends have this front clearing to the southeast by midday Tuesday. The timing may be great in preventing new initiation, but with that just as many models are hinting at a potential MCS which kinda makes the whole thing a wash strong to severe storm wise. No matter the scenario there is a potential for stronger storms, but what fluctuates are the hazards and likelihood that they actually occur. How this event unfolds as a whole and how each round plays out from the time the warm front moves in Monday to when the cold front exits Tuesday will matter. The more overworked the environment becomes with little time for recovery in between will generally mean weaker storms. Given the uncertainties here this will be a critical period to keep up to date with the forecast so you don`t get caught off guard. Beyond this looking toward mid-week, high pressure with cooler and drier air is expected to move through bringing dry weather Wednesday and Thursday. Daytime highs are expected to be at the coolest Wednesday in the low 50s to low 60s (the cooler low 50s are expected near Lake Michigan). Slightly warmer conditions are expected inland Thursday, but easterly flow of the lake will keep temps capped in low 50s to mid 60s area wide (again cooler at the lakeshore). Friday into Saturday looks like the next potential for rain and storms. Chances are still fairly low here around 10-20%. This is largely due to uncertainty in the strength and location of an upper level trough that will move from Alberta to far norther plain. Models are split on how far east this trough will get before it swings back northeast into Ontario/Quebec. Given that I wouldn`t be shocked to see trends keep the low POPs in place until there is enough confidence that this system track. The one bright side is those hopping for some more summer like temperatures may get just that as winds become southerly again for the weekend. Patterson && .AVIATION... Issued 331 PM CDT Sun May 17 2026 MVFR to IFR ceilings associated with the lingering clouds from the morning round of showers and storm linger, but should improve through the evening as the warm front lifts northward. Looking at line a of showers and storms to spread in from west to east after 03z. Some of these may be strong to severe especially for terminals west of I-39 with damaging winds be the primary threat. Could see showers and storms persist into the eastern terminals overnight through daybreak before clearing out by mid morning. Accompanying any of this activity will be lower ceilings, and visibility with the moderate to heavy rainfall. Then behind the morning stuff expect improving flight conditions through the afternoon with more southerly winds. Wagner && .MARINE... Issued 331 PM CDT Sun May 17 2026 Gusty northeast winds continue across north of the warm front across much of the lake. Expect to see the front gradually return north as a warm front overnight tonight, with winds veering southerly and becoming gusty as low pressure around 29.5 inches approaches from the west. Breezy south winds will then continue through Monday and into Tuesday followed by a wind shift to the northwest late Tuesday afternoon and evening with the passage of a cold front. High pressure and light and variable winds will then take hold from late Wednesday into Thursday. Wagner && .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