Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
212 FXUS63 KMKX 121212 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 712 AM CDT Wed Aug 12 2026 .KEY MESSAGES... - Fog is expected through the morning with patchy dense fog possible in low lying areas and along Lake Michigan. - Chance for showers and thunderstorms toward the WI/IL border and toward our central WI counties through this morning with additional shower and thunderstorm chances on Thursday. Cannot rule out a stronger storm or two with any of this activity. - Drier for Friday with an active pattern returning for the weekend with additional rounds of thunderstorms expected. - Near normal to below normal temps are expected through the weekend. && .UPDATE... Issued 706 AM CDT Wed Aug 12 2026 SPC MesoA continues to show a sharp CAPE gradient to our south directed from central IA into IL along the Interstate 80 corridor. Its likely that any MCS this morning will follow this gradient and we may end up completely dry. For now, have continued slight PoPs along the WI/IL border to account for any glancing blow from the outer edges of the MCS to our south. Otherwise the HRRR and RRFS continue to suggest the potential for scattered storms this afternoon/evening, but disagree on a definite location. For now, tend to agree the RRFS`s placement over central Wisconsin late this afternoon into the evening, given a more southward progression to the quasi-stationary frontal boundary today in the low levels and a logical progression southward from where storms fired this past night. CMiller && .SHORT TERM... Issued 1111 PM CDT Tue Aug 11 2026 Today through Thursday night: Southern WI continues to sit in between two boundaries, a surface warm front strewn across Central WI to our north and the effective warm front with the higher dewpoints/SBCAPE extending down from northern IA southeastward through IL. This will bring light and variable winds along with fog across much of southern WI overnight. As for shower and thunderstorm chances, the better potential continues to favor the effective warm front to the south given the greater instability gradient aligning with the nose of 35 kt LLJ. Latest thinking is convection upstream across SD/NE into IA will eventually congeal into another MCS and tap into another mid-level shortwave trough and track east-southeastward along the effective warm front through the morning. While the deeper cores remain south of the WI/IL border, could still see some showers along the northern peripherals of the MCS clip our southern tier of counties mid- morning into the early afternoon, but higher confidence remains to the south. Additionally, cannot rule out seeing a few isolated to scattered cells develop north of the effective front as we have seen over the past couple of nights that may be capable of producing hail. However, pinpointing if and where anything will develop remains the question as there is no distinguishable forcing mechanism at this time, just broad synoptic lift from 700-850 WAA and frontogenesis banding along with 1000-3000 J/KG of MLCAPE and plenty of CIN. Once the mid-level wave passing just to our south departs, expect PoP chances to diminishes through the afternoon with the effective warm front nudging further south into central IL this evening into Thursday morning. Will have another opportunity to see some shower and thunderstorm chances with this pattern leading into Thursday morning as another mid-level shortwave trough is expected to round the base of the slowly moving broader trough through daybreak. The main difference will be the placement of the effective warm front well to the south with the great instability, but will still have the original warm front sag into our CWA as this wave swings through. This paired with any lingering upstream convection will be enough to keep increased PoP chances through mid-Thursday morning into the early afternoon. Will have to see how things materializes as any convection may be on a diminishing trend as it moves into southern WI, but still cannot completely rule out the potential for pockets of gustier winds if this activity is able to maintain its strength as it pushes through by the early afternoon. After this activity, upper-level ridge begins to build across the Upper Midwest and influence from this activity pattern shifts away from our area leading to drier conditions Thursday night. Wagner && .LONG TERM... Issued 1111 PM CDT Tue Aug 11 2026 Friday through Tuesday: Friday continues to trend drier as the influence from the stationary front that has plagued the region with shower/storm chances over the past few days moves off as high pressure builds down the Upper Great Lakes. Looking at near to below normal temps to accompany a break in the PoPs for the end of the week. However, a trough is progged to work its way across the northern Plains into the weekend kicking the ridge axis east. This pattern will allow for a surface low in the lee of the Rockies to gradually lift northeastward across the Midwest through the day Saturday. Expect the low-level WAA and warm front to spread across southern WI ahead of this incoming system bringing increased shower and thunderstorm chances earlier Saturday. Given the latest track, this would then allow for the leading edge of instability to nudge northward into our neck of the woods through the afternoon into early evening to support thunderstorms with any activity that develop ahead and along the cold front. Currently not favoring strong or severe development with this round as upper-level jet remains to our north and lack deep layer shear. However, still plenty of uncertainty in the low`s track, timing, and how far north the higher instability reaches, but it is not out of the realm of possibility, just unlikely at this time. Expect the cold front to slide through either later Saturday night or on Sunday, which would keep PoP chances around longer. Nevertheless, expect high pressure and a drier airmass to settle in later Sunday into the start of next week. Wagner && .AVIATION... Issued 710 AM CDT Wed Aug 12 2026 Expect fog to linger into the mid morning hours before mixing out. Low clouds will then persist this morning before gradually rising and scattering. Storms this morning should stay south of the WI/IL border. If anything a glancing blow may be dealt to KJVL and KENW. Winds will remain light and variable through the TAF period. CMiller && .MARINE... Issued 1111 PM CDT Tue Aug 11 2026 Light and variable winds are expected to continue through Thursday as a stalled frontal boundary remains south of the Lake bringing periodic shower and thunderstorm chances for southern portions of Lake Michigan along with patchy fog. Influence from this front finally moves away from the region as high pressure builds down across the Great Lakes region Thursday night into Friday. Will see south to southeasterly winds increase into the weekend as the high pressure slides east of the area while low pressure develops over the Plains. Expect this low pressure to track northeastward across the Upper Great Lakes later Saturday into Sunday bringing shower and thunderstorm chances to the Lake. Behind this departing low pressure, winds shift to the northwest later Sunday into early next week as another high pressure builds down across the region. Wagner && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Dense Fog Advisory...LMZ643-LMZ644-LMZ645 until noon Wednesday. && $$ 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