Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
063 FXUS63 KMKX 011901 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 201 PM CDT Thu Oct 1 2026 .KEY MESSAGES... - Widespread rain gradually ends from northwest to southeast by mid-evening. Brief heavy downpours & nuisance impacts (ponding of water on roads, minor rises on creeks/streams) are possible in far southeast Wisconsin. - Chilly overnight temps could lead to areas of patchy frost Friday night & early next week. && .SHORT TERM... Issued 210 PM CDT Thu Oct 1 2026 This Afternoon through Sunday: Synopsis/Mesoanalysis: Reflective of split upper level flow in place across the Upper Midwest, a busy surface pattern prevails early this afternoon regionally. Beneath the southern stream, a weak surface low has been noted near the Burlington, Iowa vicinity. A warm front extends east-northeast from the low, with 1 PM observations placing the boundary along an approximate Rochelle, IL - Waukegan, IL axis. Overrunning rain showers continue in south-central and southeast Wisconsin to the north of the front. Further north/beneath the northern stream, a cold front extends from near Stevens Point to La Crosse, and will slowly progress into the area from late afternoon into this evening. Much drier air will funnel in behind the front, acting to shut down rain from northwest to southeast by mid-evening. The front will clear south of the Wisconsin-Illinois border during the second half of the overnight, with northerly winds and much drier air in place areawide by daybreak. High pressure will move across the area Friday & Friday night, bringing clear skies and chilly temperatures for early Saturday morning. The high will shift east Saturday through Sunday, bringing a modest warm up through the weekend. This Afternoon & Early Evening: Expect areas of widespread showers to gradually contract southeastward ahead of the arriving cold front. Anticipating that the most widespread & steadiest activity will focus along & south of I-94/US-18, where an overlap of overrunning FGEN, moisture transport, and elevated precipitable water values will reside. Can`t rule out some heavy downpours & localized/nuisance hydro impacts in far southeast Wisconsin, though general expectations are that the southward-moving cold front & affiliated dry air push will shunt any locally heavy rain & flooding potential into northern Illinois. Have thus held off on bringing any Flood Watches into far southeast Wisconsin in the mid-day update, but will be monitoring trends for an isolated Flood Advisory into early evening. Conditions should dry out by midnight. Friday night: With high pressure moving overhead, anticipate that efficient radiational cooling will lead to chilly overnight lows near or slightly below 40 degrees away from Lake Michigan. Depending on how cool temperatures get, could see some patchy frost in low- lying inland areas. Not expecting any frost to be widespread enough for headlines at this time. Be sure to bring any cold-sensitive plants indoors. Saturday night: Can`t rule out a few light showers across far northern counties as an upper disturbance moves across the Upper Peninsula of Michigan. Have introduced some 10-15% precip probs in the mid-day update to account for this potential. Not expecting any hazards in any precip that occurs. Quigley && .LONG TERM... Issued 210 PM CDT Thu Oct 1 2026 Sunday night through Thursday: Synopsis: A pronounced area of Canadian high pressure will build into the western Great Lakes Sunday night through Monday, bringing light winds and very dry air to southern Wisconsin. The light winds will combine with attendant clear skies to support efficient cooling during the overnight periods Sunday into Monday & Monday into Tuesday, with areas of frost possible during each time frame. The high will vacate east of the area on Tuesday, with a weak disturbance and surface front progged to track across the area Tuesday night into Wednesday. A few showers could develop in the vicinity of the passing disturbance & front, with hazards appearing unlikely. Dry conditions will prevail through the remainder of the period behind the departing upper disturbance & surface front. Tuesday night into Wednesday: The lone (albeit very small) precip chances of the period enter ahead of a weak upper disturbance and cold front. Precip probabilities from the NBM are currently in the ~10-20% range, which is a testament to a very dry antecedent air mass & marginal frontal convergence. With the values appearing reasonable given environmental limitations, have thus maintained NBM precip probabilities in the mid-day update. Modeling points toward marginal CAPE & precipitable water values, suggesting low hazards potential in any precip. Will nevertheless monitor trends as this portion of the period draws closer. Quigley && .AVIATION... Issued 210 PM CDT Thu Oct 1 2026 Wide range of flight categories prevails early this afternoon across southern Wisconsin as widespread RA continues. Generally seeing the bulk of MVFR & IFR reductions focusing over the southeast half of the area, with greater prevalence of VFR conditions further northwest. Expect RA to continue through the near-term, with widespread coverage gradually contracting toward southeast Wisconsin by early evening. Decreasing precip coverage will be accompanied by increases in VIS and CIG readings. Have adjusted the near-term forecasts at all terminals to align with observational and short term forecast trends. Debated carrying PROB30 -RA groups for several hours beyond the conclusion of prevailing mentions, but ultimately refrained given ongoing widespread precip. Will modify prevailing RA groups where necessary as conditions dictate into this evening. Expecting precip to shunt southeast of the region by mid-evening, with low-mid level clouds scouring out through the second half of the overnight hours tonight. Quigley && .MARINE... Issued 210 PM CDT Thu Oct 1 2026 Showers & a few rumbles of thunder will continue across the southern half of Lake Michigan into this afternoon ahead of an approaching cold front. The front will work across the waters this afternoon & evening, bringing a north-northwest wind shift. Winds will be breezy behind the front, though gales are not expected. 1024 mb high pressure will move across Lake Michigan Friday afternoon into Saturday, bringing decreasing & eventually light/variable winds. Winds will trend south-southwesterly Saturday as 1010 mb low pressure moves toward the Hudson Bay from the Canadian Prairies. The low will pull a cold front across the waters Saturday night into Sunday, bringing a west-northwest wind shift. Showers could accompany the passing front, particularly across the northern half of the waters. Northwest winds will continue through the day Monday, tapering Monday night as 1024 mb high pressure moves in from the northern Great Plains. A deeper area of 994 mb low pressure will build toward the Hudson Bay Tuesday through Thursday. South-southwest winds will increase in advance of the approaching low Tuesday afternoon through Wednesday, becoming gusty at times. While not currently expected to be widespread, a few gusts could approach gale-force. Will be monitoring for possible upward trends as this portion of the period draws closer. The low will pull a cold front across the waters Wednesday night into Thursday, bringing a northwest wind shift and scattered rain showers. Elevated wave heights could lead to periods of Small Craft Advisory conditions south of Wind Point late tonight into Friday morning. A Small Craft Advisory is now in effect between 4 AM & 1 PM Friday from Wind Point to Winthrop Harbor given these expectations. Additional Small Craft Advisory conditions are possible Tuesday night into Wednesday ahead of the next area of low pressure. Will be monitoring for potential headlines as this portion of the period draws closer. Quigley && .HYDROLOGY... Issued 210 PM CDT Thu Oct 1 2026 Long-duration rainfall event is approaching its conclusion this afternoon. Expecting additional steady to briefly heavy rainfall in far south-central and southeast Wisconsin through mid-evening, with conditions drying out thereafter. Flash flooding potential is low in additional rainfall, though ponding of water on roads, minor rises on creeks/streams/rivers, and isolated urban/small stream flooding can`t be ruled out in far southeast Wisconsin. A Flood Watch is now in effect along the Fox River at New Munster given the expected additional rainfall & a resultant rise to near 12.1 feet by early Friday morning. Will be monitoring observational trends into this evening & upgrading to a Flood Warning if/when conditions warrant. Quigley && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Small Craft Advisory...LMZ646...4 AM Friday to 1 PM Friday. && $$ 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