Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
043 FXUS63 KMKX 010357 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1057 PM CDT Wed Sep 30 2026 .KEY MESSAGES... - Moderate to heavy rain will spread into southern Wisconsin mostly after 3 AM CDT Thursday and last through the morning. on average, 1.5 to 2.25 inches of rain is forecast through Thursday, but much less toward central WI. Urban and small stream flooding and isolated flash flooding will be possible where locally higher rain amounts occur. Otherwise, rises in rivers and low lying areas are expected. && .SHORT TERM... Issued 1057 PM CDT Wed Sep 30 2026 Tonight through Thursday night: The forecast for widespread mdt to heavy rainfall remains on track for late tnt-Thu AM. A wave of low pressure over central KS will track to ern IA by 12Z Thu, while a shortwave trough over NE into nw IA approaches srn WI during this time. The nose of a swly low level jet of 40-45 kt will set up over far srn WI. Deep, sloping frontogenesis will develop across the region as the low and aforementioned features shift across srn WI into lower MI on Thu. The strong lift will occur within a saturated troposphere and PWATs around 2 inches. Thus high precipitation efficiency is expected. The mean flow will be fairly fast, but several hours of mdt to heavy rain will still occur for most locations. Rainfall amounts of 1.5-2.25 inches are forecast with locally more. Urban and small stream flooding and isolated flash flooding will be possible where those locally higher amounts occur. There is some confidence based on CAMs that a band of the heaviest rain will stretch from far sw WI into the Madison area. Rainfall amounts toward central WI will be much less. The widespread rain will continue over se WI for the afternoon followed by cooling and drying from the north afterward. Skies will gradually clear Thu nt on nly winds and cold and dry air advection. Temps will remain in the 60s tnt and tomorrow then fall into the middle 40s to lower 50s by sunrise Friday. Gehring && .LONG TERM... Issued 1057 PM CDT Wed Sep 30 2026 Friday through Wednesday: The models have fairly good agreement for the overall pattern this weekend into next week. Nly winds and weakening cold advection will prevail on Fri followed by high pressure around 1027 mb for Fri nt. After a relatively cool day in the lower 60s, low temps will fall into the middle 30s to lower 40s inland from the lake. Patchy frost will be possible around sunrise Sat north of Madison. A west to northwesterly flow aloft will prevail for the weekend into the middle of next week. A shortwave trough and sfc low will track across the Canadian border over the Great Plains on Sat, with the low to deepen and track into central Ontario for Sat nt. Sly winds and warm advection will return to srn WI followed by a dry cold front Sun AM. High temps will warm through the 60s for the weekend. A surface ridge will pass on Mon followed by another low across central Canada bringing sly winds to srn WI on Tue. Relatively cool temps on Mon will warm a bit for Tue, followed by another cold front and upper trough passage on Wed. There is uncertainty on whether this front will be a dry passage, but the forecast is dry at this time. Gehring && .AVIATION... Issued 1057 PM CDT Wed Sep 30 2026 Cigs well below 1 kft will develop this evening and last through Thu AM, then lingering into the afternoon over SE WI. Vsbys of 2-4SM via BR and drizzle will prevail this evening then dropping to 1-2SM via BR and widespread rainfall during the overnight and much of Thu AM. Local 1/2SM FG will be possible during this time. The widespread rain will continue over SE WI during the afternoon with low Cigs and vsbys continuing. Cigs and Vsbys will then rise to MVFR then VFR from nw to se across srn WI from late afternoon into the evening. Gehring && .MARINE... Issued 1057 PM CDT Wed Sep 30 2026 Modest southwest winds will continue tonight then shift westerly ahead of a cold front by the middle of Thursday. Expect winds to then shift northwest with the frontal passage Thursday afternoon. Modest to breezy northerly winds are then forecast Thursday night and Friday. Strong high pressure around 30.4 inches will then overspread the Great Lakes Friday night. This should bring lighter winds to the lake Friday night into Saturday. A fast-moving low pressure system around 29.8 inches should move across or north of Lake Superior Saturday night, with high pressure around 30.4 inches moving southeast into the region by early next week. South to southwest winds Saturday night should veer northwest to north Sunday into Monday across Lake Michigan. Gehring && .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