FXUS63 KMKX 222234 AAA AFDMKX Area Forecast Discussion...UPDATED National Weather Service Milwaukee/Sullivan WI 534 PM CDT Sat Aug 22 2026 .KEY MESSAGES... - Scattered showers & thunderstorms over east-central and southeast Wisconsin through early this evening. A few storms could produce gusty winds to 40 MPH. - An isolated waterspout or two are possible over Lake Michigan through tonight. - Dry and pleasant conditions into the beginning of next week. Storm chances return Tuesday evening into Wednesday. && .UPDATE... Issued 534 PM CDT Sat Aug 22 2026 Scattered showers and storms in the east due to a weak wave and lake breeze interaction will continue into early evening. Activity is expected to wind down quickly though as daytime heating is lost. Mostly clear skies, light winds, and decreasing dewpoints are then expected tonight as high pressure builds in, with lows a few degrees below normal around the low 50s most places. DDV && .SHORT TERM... Issued 1145 AM CDT Sat Aug 22 2026 This afternoon through Sunday night: Synopsis/Mesoanalysis: Fair weather cumulus are developing late this morning as surface heating commences within modest low level moisture still in place. While subtle, 11 AM surface observations identify a weak surface boundary extending from near Green Bay west toward the Black River Falls vicinity. Modest north-south moisture differences, in addition to slight cyclonic surface convergence, have been noted across the boundary through the late morning hours. Anticipate that this surface front will continue to sag south into east-central and southeast Wisconsin this afternoon, with its affiliated surface convergence providing just enough lift for scattered showers and thundershowers mainly along/east of a Ripon- Lake Mills-Lake Geneva line. Not expecting much in the way of hazards in any activity, although the strongest thundershowers could produce a few cloud to ground lightning strikes and wind gusts to 40 MPH. Keep an eye on the sky if planning to be outdoors across the east this afternoon. Currently centered along the North Dakota- Manitoba border, high pressure will gradually shift into the Upper Mississippi Valley tonight, ultimately moving overhead on Sunday night. The high's approach & arrival will maintain a Canadian air mass across southern Wisconsin tonight through Sunday night, leading to fall-like conditions during the overnight periods. This Afternoon: Monitoring for a gradual increase in shower/thundershower coverage across the east as a weak surface boundary works in from the north. Expect that most activity will generate as the aforementioned boundary impinges upon the more focused area of cumulus clouds currently evident from Ripon- Sheboygan south to Burlington-Milwaukee. Have thus continued 20-40% precip probabilities along & east of a Ripon-Lake Mills-Lake Geneva line in the mid-day update. Severe weather threat is low in any development given modest instability & weaker along-boundary convergence, though steep low level lapse rates & deeply mixed boundary layers could support isolated wind gusts to 40 MPH in any collapsing precip cores. A few cloud to ground lightning strikes are possible as well. Keep an eye on the radar if planning to be outdoors across the east this afternoon. Quigley && .LONG TERM... Issued 1145 AM CDT Sat Aug 22 2026 Monday through Saturday: Synopsis: High pressure will continue across the state on Monday, leading to plentiful sunshine & continued dry conditions with low humidity. The high will shift east of the region on Tuesday, with southerly return flow allowing for gradual moisture returns and slight increases in humidity. The next upper disturbance and surface front will drift into the western Great Lakes from the Canadian Prairies Tuesday evening through Wednesday, bringing the next chances for showers and thunderstorms to southern Wisconsin. Disagreement amongst global guidance regarding the timing of the forcing mechanisms casts some uncertainty over how many rounds of storm development will occur, in addition to storm intensity. Trends will be monitored over coming forecasts. A new area of high pressure will move into the western Great Lakes during the second half of the week, leading to pleasant and mostly dry weather conditions Thursday into Friday. The high will shift east by Saturday. Tuesday Evening through Wednesday: The best thunderstorm chances of the long term period enter the forecast ahead of an upper wave and cold front. Current blended & ensemble guidance generally points to a warm sector spreading into the area Tuesday evening/night, with the trailing cold front then pushing through at some point during the day Wednesday. Precip forecasts from the NBM thus like the idea of an initial batch of storm development within the warm advection regime Tuesday evening/night, followed by additional development along the passing cold front at some point on Wednesday. Available deterministic guidance, however, muddies this picture, with a number of different scenarios being depicted regarding the evolution of both the surface pattern & flow aloft. Have thus trended the precip forecast toward the blended/ensemble scenario at this point, with the understanding that some changes are likely to occur into early next week given the noted range of solutions in the deterministic suite. Aforementioned questions regarding the extent and quality of the warm sector make the potential for any strong/severe storms unclear in this forecast, though prevailing deep layer shear would be sufficient for at least some storm organization in the event timing & spacing allowed for enough destabilization. Will be monitoring trends and providing more details as this portion of the period draws closer. Quigley && .AVIATION... Issued 534 PM CDT Sat Aug 22 2026 Scattered showers and storms in the east due to a weak wave and lake breeze interaction will continue into early evening. Activity is expected to wind down quickly though as daytime heating is lost. Winds will waffle between northeast and northwest toward Lake Michigan, as the lake breeze stalls though early evening. Mostly clear skies and light winds are then expected tonight into early Sunday as high pressure builds in. Scattered VFR cumulus and modest northwest winds are likely late Sunday morning into the afternoon. DDV && .MARINE... Issued 1145 AM CDT Sat Aug 22 2026 1010 mb low pressure is centered over the southern Hudson Bay this morning, resulting in generally northeast winds across the open waters of Lake Michigan. These winds will continue into this evening as a weak cold front moves across the lake and 1023 mb high pressure builds into the northern Great Plains. Isolated showers and thunderstorms are possible along the passing front this afternoon & evening. Severe weather potential is low in this activity, though an isolated stronger storm with gusty winds or a waterspout can't be entirely ruled out. Will be watching radar trends for any potential marine weather statements or special marine warnings through this evening. Northwest winds will continue through the day Sunday, ultimately weakening by Sunday night as the aforementioned area of high pressure approaches Lake Michigan. Light and variable winds will continue Monday with high pressure lingering in the vicinity. The high will shift east into Ontario by Tuesday, resulting in a south-southwest wind shift across the waters. 1005 mb low pressure will approach from the northern Great Plains Tuesday night into Wednesday, reinforcing the south- southwesterly wind pattern. The low will cross Lake Michigan during the second half of the day Wednesday, bringing a northwest wind shift. Gales are not expected as this occurs. Showers and thunderstorms will accompany the approaching/passing surface low Tuesday night into Wednesday afternoon. It remains too early to tell if any of these storms could be severe, with trends being monitored into the beginning of next week. Scattered showers and thunderstorms are possible in nearshore zones this afternoon as a weak cold front moves south across Lake Michigan. An isolated stronger storm with gusty winds or an isolated waterspout can't be entirely ruled out. Increasing southerly winds and wave heights may lead to a brief period of Small Craft Advisory conditions Tuesday afternoon & evening, particularly to the north of Milwaukee. Will be monitoring trends & evaluating the need for any headlines through the beginning of next week. The next thunderstorm chances arrive Tuesday evening through Wednesday, with severe weather potential uncertain at this time. 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