Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
956 FXUS63 KMKX 220304 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1004 PM CDT Thu Aug 21 2025 .KEY MESSAGES... - More fog/low stratus potential later tonight into early Friday morning, especially west of Interstate 90. Patchy dense fog may occur. - Next chance of showers/a few storms is Friday night into early Saturday morning with a cold front. - Much cooler, less humid, and breezy from later Saturday into early next week. && .UPDATE... Issued 1004 PM CDT Thu Aug 21 2025 Cloud cover has largely dissipated tonight, with temperatures beginning to fall toward the dewpoints across much of southern Wisconsin. Fog potential will be battling between the calm winds and rapid radiational cooling under clearing skies and subsidence bringing lower dewpoints toward the surface and preventing saturation. Confidence in fog formation remains highest in southwestern Wisconsin, where some fog may become dense, and lowest in southeastern Wisconsin where lakeshore temperatures remain warmer and the greatest dry air subsidence is expected to occur. MH && .SHORT TERM... Issued 237 PM CDT Thu Aug 21 2025 Tonight through Friday night: The current area of low stratocumulus clouds has been rather slow to mix upwards and become more broken in nature, despite daytime heating. These clouds may linger into this evening or perhaps overnight into Friday morning, as high pressure lingers over the region. Confidence is somewhat low with if and when these clouds scatter out into this evening and overnight. For now, will continue to have them dissipate this evening, but more forecast adjustments upwards with the cloud cover may be needed. This would also limit the fog potential overnight into Friday morning. If the clouds can scatter out, there should be some fog development in western parts of the area during this period, with patchy dense fog possible. More low stratus clouds may form as well. The forecast will hinge on the current low clouds scattering out this evening. Lows in the upper 50s to around 60 are forecast, a little higher near the lake. Light southwest winds Friday with some scattered to broken stratocumulus clouds are anticipated, especially if they linger from the overnight/early morning hours. Highs in the upper 70s to around 80 degrees are expected. Models continue to bring a cold front southeast through the area later Friday night into early Saturday morning, with the NAM slower and more moist and unstable than the other models. NAM has shown this more aggressive trend for a day or two now, but seems overdone, so will keep 20 to 40 percent chances for essentially scattered showers and a few storms Friday night. This is supported by the CAMs, which at best show scattered showers and little in the way of convection with the frontal passage. Wood && .LONG TERM... Issued 237 PM CDT Thu Aug 21 2025 Saturday through Thursday: Steady cold air advection with west northwest winds on Saturday should increase into Sunday and Monday, as the pressure gradient increases. This is in response to low pressure deepening and occluding over northern Ontario later Saturday into early next week, which has been indicated by 500 mb cluster analysis. After one last mild day Saturday, this setup should bring well below normal temperatures for Sunday into Tuesday, which is supported by ensemble and NBM trends. Highs in the middle to upper 60s and lows in the 40s inland are looking more likely during this period. In addition, various vorticity maxima at 500 mb rotating through the region at times may bring some scattered shower chances, though it is difficult at this time to pinpoint. The occluded low should move east of Ontario later in the week, with a ridge approaching the region from the west. This should allow for continued dry conditions under high pressure, but allow for temperatures to return closer to seasonal normal values. Wood && .AVIATION... Issued 1004 PM CDT Thu Aug 21 2025 Cloud cover has largely dissipated tonight, with fog potential remaining across southwestern Wisconsin late tonight into early Friday morning. Current expectation is that only patchy dense fog, primarily from JVL and MSN westward, is expected, with areas to the east remaining too dry to produce dense fog. Still, patchy fog and visibilities in the 3 to 5 SM range remain possible. Fog and any subsequent low stratus will dissipate shortly after sunrise. Winds will become southwesterly on Friday, with VFR scattered to broken diurnal cumulus developing by midday. Friday night, expect slowly increasing cloud cover ahead of a cold front that will bring scattered showers with an isolated thunderstorm or tow, as well as a wind shift to west-northwesterly. MH && .MARINE... Issued 237 PM CDT Thu Aug 21 2025 High pressure around 30.1 inches will linger over the region tonight into lingering into Friday, before weakening. Winds will generally be north to northeast across southern portions of the lake into this evening, before weakening by later tonight. Lighter winds are expected to the north, becoming south to southwest later tonight. Winds turn south to southwest Friday afternoon across all of the lake, ahead of a strong cold front, which will pass across the lake Friday night into Saturday morning. Scattered showers and a few thunderstorms are possible along this front. Gusty west to northwest winds are expected from late Saturday into early next week behind this cold front, as low pressure around 29.5 inches strengthens over northern Ontario. These gusts may reach Small Craft Advisory levels at times during this period for the nearshore waters. In addition, there may be enough delta T values and convective cloud depth over northern portions of the lake for a few waterspouts to develop Sunday into Monday, as the deep upper level low pressure system moves into northern Ontario. May need to add this mention into the Open Waters Forecast if this trend continues. Wood && .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