FXUS63 KGRB 081813 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 113 PM CDT Wed Jul 8 2026 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Scattered strong to severe thunderstorms remain expected this afternoon and evening, mainly between 3 and 8 PM over central and east-central Wisconsin. Damaging winds are the primary threat. - Torrential rainfall rates of 2 to 3 inches per hour within the strongest storms will create a risk for localized flash flooding, especially in urban, low-lying, and poorly drained areas. - Trends continue to be monitored for the excessive heat potential early next week. && .DISCUSSION... Issued at 112 PM CDT Wed Jul 8 2026 The latest RAP analysis and satellite/radar imagery show a cold front stretching from west-central to north-central Wisconsin early this afternoon. Morning showers and storms have exited over northern Lake Michigan, giving way to partial clearing across central and east-central Wisconsin where temperatures have warmed into the lower 80s. Cooler temperatures in the lower to middle 70s persist across the north where cloud cover and rainfall were more widespread. Cloud cover is becoming more extensive again over southern Minnesota in association with a remnant MCV. Focus of this forecast remains on the severe weather and flash flooding potential through this evening. Severe Weather and Flood Outlook: Destabilization is actively taking place early this afternoon over central and east-central Wisconsin where mixed- layer CAPE is climbing upwards of 1000 J/kg. With further solar heating, thunderstorms are expected to redevelop in a buoyant airmass south of the front and across central Wisconsin in the 18-20Z time frame. These storms should track east through the afternoon before propagating southeast this evening as a cold pool becomes established. Deep layer shear of 25 to 35 knots is expected in the area of greatest concern across central and east- central Wisconsin. This shear profile will be supportive of a few bowing structures and perhaps an isolated supercell. Given the modest shear aloft, conditions will be most favorable for damaging wind gusts rather than severe hail. High freezing levels around 15,000 feet and poor mid-level lapse rates do not favor large hail, except within the strongest rotating updrafts. A weak, isolated tornado will also be possible, most likely focused along an outflow boundary or lake breeze where low- level vorticity is enhanced. The greatest period of concern is from 3 to 7 PM before storms shift south and east of the forecast area. Scattered shower and storm activity could persist into the overnight period, but a stabilizing atmosphere should keep intensities below severe levels. Upper-level flow will be nearly parallel to the surface front within a corridor of precipitable water values approaching 2.00 inches and high freezing levels. High rainfall rates of 2 to 3 inches per hour are expected in the strongest storms, which could lead to localized flash flooding in vulnerable urban, low-lying, and poorly drained areas. Fog Potential Late Tonight: After the rain winds down late tonight into Thursday morning, there is a decent signal for fog development, particularly across central to north-central Wisconsin where clearing will occur first. Considerable uncertainty exists regarding how long showers stick around into Thursday. A moist boundary layer, weak cyclonic flow in the low levels, and weak shortwave impulses aloft could keep light showers lingering into the afternoon over central and east- central Wisconsin. Excessive Heat Outlook: An amplified upper air pattern featuring a dominant upper- level ridge is expected to build northeast into the region Friday through the weekend and persist into early next week. High pressure at the surface will slide across the area Friday through the weekend. While minor signals for spotty shower activity exist in some medium-range guidance, forcing is non- existent beneath the building ridge, and a dry forecast has been maintained. The primary story in the extended period will be potential for excessive heat. Very warm air aloft will accompany the building ridge will argue for surface high temperatures climbing into the upper 80s to lower 90s by Monday and Tuesday. Coupled with humidities remaining high, minor heat- related impacts appear possible at this time for those outdoors. Some relief from the heat and humidity is expected towards the middle to end of the next work week as the ridge begins to suppress southward. && .AVIATION...for 18Z TAF Issuance Issued at 1153 AM CDT Wed Jul 8 2026 Late this morning, a cold front stretches from west-central Wisconsin to north-central Wisconsin. MVFR to IFR ceilings exist along and north of the front while VFR conditions prevail to the south and south of RHI. This front will provide the focus for clusters of showers and storms this afternoon and evening. Thunderstorm redevelopment is expected 19-20Z with impacts into RHI/AUW/CWA starting during this timeframe. These storms are expected to increase in coverage and proceed into the Fox Valley in the 22-23Z period. Strong storms are likely with gusts in excess of 40 mph possible with ceilings and visibilities falling to MVFR and IFR/LIFR respectively. After the initial push of storms, scattered showers with embedded thunder looking to continue through much of the evening, while light showers could persist across parts of central and east- central WI into Thu morning. Late tonight, there is a decent signal for ground fog to develop. Central and north-central WI have potential for sub-IFR visibilities. The fog should lift into a MVFR stratus deck after about 15Z. Winds will be light over the period. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....MPC AVIATION.......MPC