Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
632 FXUS63 KMKX 081430 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 930 AM CDT Fri Aug 8 2025 .KEY MESSAGES... - Hot and humid today with heat index values between 95 and 100 over much of southern WI this afternoon. Heat indices may again reach 95 to 100 over southeast Wisconsin Saturday. - A moderate swim risk is anticipated over Sheboygan and Ozaukee Counties this afternoon into tonight. A high swim risk is then anticipated tomorrow for the same counties, with a moderate swim risk for Milwaukee and Racine Counties. - Potential for multiple rounds of thunderstorms from Saturday into next week is increasing. Heavy rain/flooding may become a concern if multiple rounds of storms affect the same areas. && .UPDATE... Issued 930 AM CDT Fri Aug 8 2025 Upper ridging and capping will continue to build over central and srn WI today into this evening. Southerly surface winds will maintain a hot and humid airmass over srn WI today into Saturday. Heat index values are on track to warm into the upper 90s today with relief near Lake MI. Cloud trends for Sat AM into the early afternoon are a bit uncertain as a decaying MCS may approach from the northwest, but overall believe its likely hot and humid conditions will occur before more robust convection and heavy rain for the afternoon and evening over south central WI, spilling into portions of se WI as well. Gehring && .SHORT TERM... Issued 436 AM CDT Fri Aug 8 2025 Today through Tonight: Patchy morning fog will be possible until daytime mixing kicks in after dawn. Today should then largely remain mostly sunny to partly cloudy. We`ll likely remain capped under the ridge and remain dry, as RAP soundings show a warm nose to 13 C around 700mb over much of southern WI. No sfc triggers are anticipated to play a role in driving storm development, as significant fronts/troughs will remain west of the area and a lake breeze will be muted today amid stronger southerly winds. With ample sunlight and warm temps aloft, highs will rise into the low 90s amid surface dew points in the low 70s. Heat index values are anticipated to reach between 95 and 100, with a few scattered areas touching 100. Given the more scattered and marginal nature of heat indices reaching criteria rather than a slam dunk, have opted to hold off on the issuance of a heat advisory at this time. With the elevated southerly to south southeasterly winds over the waters, moderate swim risk conditions will occur at beaches in Ozaukee and Sheboygan Counties. Breaking waves and currents are expected, especially near shorelines structures such as piers and breakwalls. A reprieve from the heat isn`t anticipated tonight as overnight lows are expected to fall into the low 70s. CMiller && .LONG TERM... Issued 419 AM CDT Fri Aug 8 2025 Saturday through Thursday: As the positively-tilted ridge axis makes eastward progress into this weekend, persistent troughing over the northern Great Plains parks the jet stream over Minnesota / northern Wisconsin, with occasional shortwave perturbations rolling through, triggering occasional chances for showers and thunderstorms. Timing any specific round of shower / storm activity is incredibly challenging at this time, as each round of convection sets the antecedent environment for the next round (throwing model guidance off course), and as things currently stand, the timing of the 500mb shortwaves is inconsistent from one model to the next. A baroclinic zone eventually evolves, likely stalling over our region Sunday into the first half of next week, resulting in continued shower / thunderstorm chances. Pinpointing the axis of heaviest rainfall is difficult, but it appears possible for some locations to see several inches of rain between Saturday and mid next week, and multiple rounds of showers / storms are expected through said window. As trends become more evident it is possible that a flood watch may eventually be needed. A potent Low Level Jet spanning SW to NE over Iowa and bisecting Wisconsin predawn Saturday morning may be accompanied by some nocturnal convection, which could gradually meander eastward into our CWA Saturday AM (roughly 10-25% precip chances to account for this). As the LLJ translates eastward throughout Saturday, expecting south-southwesterly surface winds to become a bit breezy (with gusts to 25 MPH). Winds over Lake Michigan may remain due southerly and gust closer to 30 MPH, which would allow wave heights to build, with High Swim Risk Conditions possible on Saturday, particularly for Sheboygan and Ozaukee county beaches. An accompanying Small Craft Advisory may also be needed. Temperatures top out in the upper 80s to low 90s Saturday afternoon (presuming skies remain mostly clear and convection holds off). Precip chances build into Saturday evening and night, accounting for a model-resolved convective complex, developing to our northwest underneath the 250mb jet entrance region, gradually tracking southeastward and producing a pseudo frontal boundary. As previously stated, the timing and existence of this convective feature are far from certain, but PWAT values around 2 inches and modest to strong instability would be present out ahead of it if things could get organized. Hence, localized heavy rainfall and a few stronger storms would be a possibility. The baroclinicity from the aforementioned convection evolves into a stationary boundary, resulting in continued chances for showers and thunderstorms Sunday and onwards (through the first half of next week). High temps fall to the mid 80s Sunday, primarily on account of increased potential for cloud cover. Likely a similar outcome through the first half of next week. Southwest winds continue, a tad less breezy than Saturday on most guidance. The slightly offshore and slightly weaker wind flow should help reduce the swim risk and nearshore marine wave heights Sunday and onwards. Sheppard && .AVIATION... Issued 930 AM CDT Fri Aug 8 2025 VFR conditions today into Saturday with persistent south winds preventing fog formation at night. Numerous thunderstorms are expected to develop over south central WI Saturday afternoon over south central WI, with some storms possibly moving into se WI. Bkn035 cumulus congestus would be expected in the afternoon with lower Cigs and Vsbys in and near storms. Gehring && .MARINE... Issued 419 AM CDT Fri Aug 8 2025 After some isolated morning ground fog, mainly dry conditions will contribute to VFR conditions through today into tonight. Winds will remain persistently southerly, with gusts up to 20 knots this afternoon. CMiller && .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