Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
096 FXUS63 KMKX 291448 AAA AFDMKX Area Forecast Discussion...UPDATED National Weather Service Milwaukee/Sullivan WI 948 AM CDT Fri Aug 29 2025 .KEY MESSAGES... - Beach Hazards Statement continues through 7 AM this morning at all Lake Michigan beaches. - Slight chances (~15-25%) for a few scattered showers and thundershowers this afternoon & evening. - Dry conditions with a gradual warming trend this weekend into early next week. - Next shower and thunderstorm chances (~40-60%) return to the forecast Wednesday into Thursday. && .UPDATE... Issued 948 AM CDT Fri Aug 29 2025 The area of showers currently over west central WI is holding together and is expected to reach Wisconsin Dells and areas north around 11 AM. These should keep sliding ESE through southeast WI into the early evening, but a lake breeze may help diminish the intensity of showers (potentially decreasing to sprinkles). Meanwhile, a shortwave dropping south from Ontario will drop through southern WI this evening. This may help to reinvigorate any ongoing showers through the overnight hours. As for lightning chances, both features have a narrow area aloft that will allow for very weak instability and therefore a lightning chance. However, the chance is low (slight, under 25%). Cronce && .SHORT TERM... Issued 337 AM CDT Fri Aug 29 2025 Today through Saturday: Synopsis/Mesoanalysis: A broad area of surface high pressure extends from Lake Superior toward the Bay of Green Bay early this morning, resulting in light and variable surface winds across southern Wisconsin. Nighttime microphysics imagery shows low clouds near the Lake Michigan shoreline, where light east-northeast winds have pulled marine air inland. Fog is beginning to fill in over the Wisconsin River Valley, with more isolated pockets of ground fog having been reported in low-lying spots along the Kettle Moraine and over far south-central Wisconsin. The lake effect clouds and valley/ground fog will linger through daybreak, with both beginning to mix out after sun comes up this morning. Currently extending from the Twin Cities north to the Ontario-Manitoba border, a 500 mb shortwave & weak area of upper divergence will move into southern Wisconsin this afternoon/evening, providing enough lift for a few scattered showers and thundershowers. Precip chances will wane late tonight as the responsible forcing mechanisms shift south of the area. Dry conditions will continue through the day on Saturday as temps climb into the low-mid 70s areawide. Rest Of Overnight: Will be monitoring the progress of valley fog in the Wisconsin Valley, in addition to any areas of ground fog along the Kettle Moraine and in far south-central Wisconsin, through daybreak. Don`t anticipate widespread dense fog, but will be monitoring Wisconsin Valley obs for pockets of < 1 mile visibilities. Expect any areas of fog to dissipate quickly after sunrise. Budget a few extra minutes of travel time if taking to the roads early this morning in the Wisconsin Valley. Elevated waves will continue at all Lake Michigan beaches through daybreak, with a Beach Hazards Statement in effect through 7 AM. Exercise extreme caution if heading lakeside through sunrise. Today through Tonight: Have maintained slight chance (~15-25%) precip probabilities primarily along/west of I-41, where a pair of mid-upper forcing mechanisms will cross during the afternoon and evening time frame. A few rumbles of thunder could mix in with precip during the afternoon/early evening, particularly to the west of Madison where forecast soundings show some instability. Apart from a few flashes of lightning, hazards are not anticipated in any showers/thundershowers. Areas of fog will be possible after midnight, with some locally dense fog possible along/west of I-39. Quigley && .LONG TERM... Issued 337 AM CDT Fri Aug 29 2025 Saturday night through Thursday: 500 mb flow becomes weaker Saturday night into Monday, with a 500 mb low developing over eastern South Dakota and Nebraska Saturday night into Sunday night, shifting into western Iowa. This becomes more of an open wave on Monday and shifts to the southeast of there. An associated surface low develops beneath the upper low, with most of the precipitation remaining to the west of the area. High pressure to the east of the region helps keep easterly flow in the low levels and helps with keeping the precipitation to the west. For now, will maintain a dry forecast Saturday night into Monday, with temperatures moderating closer to seasonal normal values. There is more consensus from the 500 mb cluster analysis of the EPS, GEFS and Canadian ensembles with a rather amplified 500 mb longwave trough developing over the Great Lakes region Tuesday into Wednesday and deepening into the rest of next week. This may allow for a fairly strong cold frontal passage on Wednesday, with perhaps showers at times within the cyclonic flow into the rest of the week. This would also support cooler temperatures for later in the week, which is somewhat reflected by the NBM and ensemble trends. For now, will keep NBM PoPs in the 20 to 40 percent range for Tuesday night into Wednesday night, and may need more shower chances later in the week. Wood && .AVIATION... Issued 948 AM CDT Fri Aug 29 2025 Clouds and patchy fog cleared out this morning, allowing for a return of prevailing VFR at all terminals. Scattered -SHRA and -TSRA are forecast this afternoon, with the risk progressing all the way into southeast WI. FG is possible late tonight, particularly across western portions of the area. Cronce && .MARINE... Issued 337 AM CDT Fri Aug 29 2025 1022 mb high pressure is centered over Lake Superior early this morning, resulting in east-northeast winds across the open waters of Lake Michigan. The high will settle over the Lake Michigan vicinity this morning, resulting in decreasing northeasterly wind speeds. Winds will become light and variable tonight through Saturday as the area of high pressure drifts into Lower Michigan. The high will gradually break down Sunday into early next week, though light and variable winds will persist in the absence of any organized areas of low pressure over the western Great Lakes and northern Great Plains. Prevailing south to southwest winds will become established Tuesday and Tuesday night as 1012 mb low pressure approaches Lake Michigan from Ontario. Said low is forecast to drag a strong cold front across the waters at some point Wednesday through Wednesday night, bringing a gusty northwest wind shift to all of Lake Michigan. Gusty northwest winds will continue through most of Thursday. While the current forecast keeps gusts below gale force next Wednesday- Thursday across the open waters, the potential for increasing trends will be monitored as this portion of the period draws closer. Showers and thunderstorms will accompany the passing cold front Wednesday into Thursday, with details regarding possible strong thunderstorm wind gusts or waterspouts unclear at this time. Will continue to monitor trends over the coming forecasts. Breezy northeast winds continue in nearshore zones through sunrise, with a Small Craft Advisory remaining in effect until 7 AM CDT from Sheboygan south to Winthrop Harbor. Currently anticipate that the advisory will be able to expire as scheduled with high pressure settling over Lake Michigan this morning, but will nevertheless monitor gust and wave trends through daybreak. Light and variable winds are forecast tonight through early next week as high pressure lingers over Lower Michigan. A cold front will cross Lake Michigan during the Wednesday to Wednesday night time frame, bringing a gusty northwest wind shift to all nearshore zones by early Thursday morning. Showers and storms will accompany the passing front. While the current forecast keeps winds and waves just below Small Craft Advisory thresholds, the potential for increasing trends will be monitored over the coming forecasts. Quigley && .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