Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
978 FXUS63 KMKX 140224 AAA AFDMKX Area Forecast Discussion...UPDATED National Weather Service Milwaukee/Sullivan WI 924 PM CDT Wed Aug 13 2025 .KEY MESSAGES... - River Flood Warnings remain in effect along portions of several Milwaukee metro area rivers and adjacent tributaries. Stay away from flood waters and continue to heed any remaining road closures in these areas. - Heat and humidity briefly return to the region late this week, building Friday and peaking Saturday. - Rain and thunderstorm chances return to the forecast this weekend into early next week. && .UPDATE... Issued 924 PM CDT Wed Aug 13 2025 Some middle to high clouds may move through the area overnight into Thursday morning. High pressure will remain to the northeast of the area into Thursday, which will bring dry conditions and pleasant summer temperatures. Light winds overnight into early Thursday morning may allow for light fog to develop, with the best chances in the Wisconsin River Valley. Some surface smoke may move into the northeast parts of the area and near the lake Thursday morning, though it should not reduce visibility much. Lows in the upper 50s to around 60 are expected overnight, with lower to middle 60s along the lakeshore. Highs Thursday should reach the lower 80s inland, with onshore winds keeping middle to upper 70s closer to the lake. Wood && .SHORT TERM... Issued 305 PM CDT Wed Aug 13 2025 Tonight through Thursday night: Conditions remain calm and quiet through the short term period. Diurnal cumulus clouds erode rapidly after the sun sets this evening, with mostly clear skies overnight and nearly calm wind. This will set the stage for some patchy ground fog / valley fog to develop late overnight through early Thursday morning, burning off shortly after sunrise. Simultaneously with the fog, a plume of wildfire smoke is expected to sag southward over Lake Michigan, mixing into lakeshore areas in the early morning and drifting / dispersing westward with the lake breeze flow later Thursday morning. HRRR and RAP near surface smoke output then allows the smoke to mix out into the afternoon. Sheppard && .LONG TERM... Issued 305 PM CDT Wed Aug 13 2025 Friday through Wednesday: Upper level ridging makes steady progress over the midwest region on Friday, allowing quiet weather to continue and for daytime high temperatures to climb into the mid to upper 80s. Surface winds turn due south at around 10 MPH, gradually drawing up the warmer and more humid airmass. Southerly WAA continues at the surface into Saturday, likely driving dewpoints back into the 70s. The upper level ridge axis develops a negative tilt and amplifies into this weekend, with the southern (subtropical) jet remaining nearby to our north (over Lake Superior). The right entrance of said jet streak passes just north of us, leading to some upper air divergence, with 500mb shortwave troughs passing by in some model guidance. For Northern Wisconsin (including Green Bay, closer to the jet dynamics aloft), 50-60% chances for showers and thunderstorms are forecast on Saturday. For our CWA Saturday morning and early afternoon, this manifests as a 15-45% chance, with the highest probabilities further north towards Sheboygan and Berlin, and the lowest chances towards the WI/IL border. Later Saturday (and as always, this timing may change) we would expect this thunderstorm activity to sag southward / southeastward into our region (following the Corfidi vectors), towards the higher convective instability and PWATs of 1.75 to 2.00 inches. With relatively slow corfidi vectors, high PWAT, and moderate to high instability, the threat for heavy rainfall would once again be present somewhere in our region, though exactly where this lands in Wisconsin is challenging to predict from this far out in time. Needless to say, we will be monitoring this very closely, given that some area rivers are progged to remain at elevated levels through this week due to last weekend`s heavy rainfall event. In the event Saturday`s precip potential holds off until the evening or later, daytime high temps could easily approach 90 degrees Saturday afternoon, allowing heat indices to approach triple digit territory. Into early next week, the right entrance to the subtropical jet streak remains nearby, corfidi vectors remain slow, and PWAT / CAPE has the potential to remain similarly high. So, the ingredients for a localized heavy rainfall event somewhere in the region remain in place into early next week (Saturday, Sunday, Monday, possibly Tuesday). I use the word "somewhere" in the aforementioned setup, given that the general expectation is for thunderstorms to evolve off the upper air perturbations, forming a pseudo cold front that sags south and stalls (becoming a stationary front) that could become the focal point for showers and thunderstorms with heavy rainfall. Exactly where this boundary sets up is not yet known. To be completely honest, it may not be until it does form that we know where it will stall. Ensemble Max Temperature plume diagrams reveal that on any given day through this stretch, if we have a dry morning / early afternoon period, temperatures could soar to the upper 80s or around 90. In the event of more active morning / afternoon weather, clouds would hold temperatures to the low 80s or upper 70s. Towards the middle of next week (perhaps Tuesday or Wednesday) we would likely see the end of said "ingredients" for heavy rainfall as we find ourselves on the west side of an upper trough, with surface high pressure likely becoming dominant, along with drier weather. Sheppard && .AVIATION... Issued 924 PM CDT Wed Aug 13 2025 Some middle to high clouds may move through the area overnight into Thursday morning. High pressure will remain to the northeast of the area into Thursday, before shifting east Thursday night. This will bring dry conditions. Light winds overnight into early Thursday morning may allow for light fog of 2 to 5 miles to develop. Some surface smoke may move into the Sheboygan and Milwaukee terminals Thursday morning, though it should not reduce visibility much. Light east to southeast winds are expected for terminals near the lake on Thursday, with light southeast winds further inland. Light winds will linger Thursday night, with some light fog possible once again. Wood && .MARINE... Issued 924 PM CDT Wed Aug 13 2025 High pressure around 30.2 inches will remain dominant over Ontario through Thursday, resulting in light and variable winds over the lake. The high will drift further east later this week, as a surface pressure trough deepens over the Rockies and High Plains. This will allow 10 to 20 knot southerly winds to develop Friday. Chances for showers and thunderstorms return Saturday through the first half of next week, as a cold front slowly sags southward across the lake and stalls somewhere nearby. Sheppard/Wood && .HYDROLOGY... Issued 924 PM CDT Wed Aug 13 2025 Flood Warnings remain in effect along several Milwaukee metro area rivers and their adjacent tributaries, in the wake of the heavy rainfall this past weekend. The Fox River in Waukesha is expected to continue to slowly decrease to below flood stage sometime Friday evening. The Milwaukee River and Cedar Creek at Cedarburg continue their downward trend and are expected to fall below flood stage by midday Thursday. The Menomonee River at Menomonee Falls has fallen below flood stage, and the Flood Warning has been cancelled. The Rock River at Lebanon is cresting below flood stage, so the Flood Warning has been cancelled for that location. The Fox River at New Muster is forecast to just reach minor flood stage Saturday morning, and is being monitored with a River Flood Watch. Ponding of water in areas immediately near each river segment will remain possible until each can fall below flood stage by later this week. Continue to heed any road closures in all impacted areas until river stages recede further and Flood Warnings are allowed to expire. MH/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