


Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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213 FXUS63 KGRB 241738 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1238 PM CDT Tue Jun 24 2025 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Much cooler temps today through Thursday, but it will remain quite muggy, especially today across the south. - Periodic chances of showers and thunderstorms will continue today through Friday morning. - Periods of heavy rainfall are possible at times Wednesday and Thursday. Probability of receiving over 2 inches is highest (20-40%) across central WI. && .DISCUSSION... Issued at 405 AM CDT Tue Jun 24 2025 Short Term...Today...Tonight...and Wednesday Storm / Heavy Rain Threats: Cold front has made its way well south of the area overnight and will reside in southern WI or northern IL the next couple of days. This will keep any severe weather threat very low as better surface instability will remain to our south. However, some elevated instability (up to ~900 J/kg, highest over the south) will be present to keep at least some isolated to scattered showers and stray storms around, especially this morning into the early afternoon and along/south of Hwy 29. By later this afternoon, northeast winds will usher in some more stable air, ending the threat for showers/storms for most spots. Additional shower/storm activity will spread back into the area on Wednesday as another push of higher PWATs and shortwave/FGEN forcing arrive. PWATs between 1.5-2.0" and warm cloud depths to ~14,000 ft will bring a heavy rain and localized flooding threat to any location that sees repeated showers/storms (or that received the heavier rain the last 24 hours, especially Waushara Co.), but the overall flooding threat looks low through mid- afternoon Wednesday. Temps / Humidity: It will be much cooler today and Wednesday with highs mainly in the 70s. Some 60s are expected near the immediate showers of Lake Michigan. It will remain muggy to start the day, then dewpoints will drop from north to south through the day, bringing more comfortable humidity levels later today into Wednesday. Lows tonight will be quite refreshing for some, with upper 40s and 50s over far northern WI, with lows near 60 over central WI and the Fox Valley. The east/northeast flow on Wednesday will hold high temps mainly in the upper 60s and 70s. Long Term...Wednesday Night Through Monday Mid-level fgen and an anomalously moist airmass (PWATS 1.8-1.9")will combine to produce periods of moderate to heavy rainfall Wednesday evening through Thursday morning. Ensemble and deterministic guidance both suggest the heaviest rainfall will occur generally along a corridor from southeast MN to central WI. Within this corridor NBM probs for 24 hour rainfall greater than 1.5" are 40-50% across central WI and decrease to 20-40% further east. The risk for any embedded thunderstorms through Thursday morning is low as the better instability is shunted south of a stalled frontal boundary forecast to set up across southern WI. Isolated to scattered thunderstorms do look slightly more favorable late Thursday afternoon and evening as instability builds to 600- 1000 J/kg ahead of an approaching cold front. 0-6km shear is also forecast to reach 30-40kts which may help any thunderstorms that do develop become more organized. With precipitation loading and 500- 700 J/kg DCAPE there will be a risk for a few strong microburst wind gusts, however, confidence any wind gusts reach severe criteria is low. In addition to the wind, long skinny CAPE profiles and near climatological max PWATS ~ 1.9" support a risk for heavy downpours and isolated flood concerns. Will need to monitor antecedent soil moisture from prior rainfalls to determine what areas may be most at risk of flooding. Behind the aforementioned front the region is forecast to dry out to end the week and start to weekend. However, the dry weather does not look like it will stick around for long. ML/AI convective hazard forecast show an increase chance for more thunderstorm activity Sunday into early next week. Ensemble mean 500mb flow also supports a chance for thunderstorms during this period with a deepening trough moving over the upper Midwest. Temperatures through the extended period will slowly start to warm backup with highs returning to the middle to upper 80s by this weekend. However, lower humidity levels should keep heat indices from feeling as oppressive as the past few days,. && .AVIATION...for 18Z TAF Issuance Issued at 1229 PM CDT Tue Jun 24 2025 A cold front was dropping south through central and east central WI early this afternoon. Showers, locally heavy, were ongoing across the southeast half of the forecast area, and widespread MVFR/local IFR conditions were also observed in this area. Farther northwest, much drier air and VFR conditions prevailed. These improving conditions will work their way south through the forecast area later this afternoon. Showers are expected to end in most places by late afternoon/early evening, then gradually return to the southwest part of the forecast area Wednesday morning. As this occurs, ceilings may return to MVFR in parts of C/EC WI. Gusty northeast winds will be found in parts of the Fox Valley and lakeshore areas this afternoon, otherwise light NE-E winds will be found across the area through the TAF period. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch/GK AVIATION.......Kieckbusch