657 FXUS63 KGRB 170415 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1115 PM CDT Wed Jul 16 2025 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - The warm and humid weather will come to an end tonight. Cooler and less humid on Thursday and Friday. - Small craft should exercise caution on the bay of Green Bay through late this afternoon. A Small Craft Advisory is in effect for the bay and nearshore areas of Lake Michigan tonight into Thursday morning. - An active pattern is expected Friday night through the middle of next week with periodic chances of thunderstorms. Stronger storms and heavy rain are possible at times. && .DISCUSSION... Issued at 219 PM CDT Wed Jul 16 2025 A Mesoscale Convective Vortex continues to move across the region this afternoon, bringing showers and scattered thunderstorms to the region. Some of the strongest storms could produce strong or damaging winds, an isolated tornado and torrential rainfall across central and east-central WI. This feature will also bring in additional moisture as precipitable water values at Green Bay are expected to increase to 2.11 inches late this afternoon or near the daily record supporting the likelihood of heavy rainfall. The movement of the mesoscale convective vortex will support a nearly west to east band of heavy rain across portions of central into east-central Wisconsin. The greatest rainfall is expected to fall in a corridor from Marshfield to Wisconsin Rapids to Waupaca and Wautoma to Appleton and Oshkosh east to Kewaunee and Manitowoc. For locations south of Highway 29, HREF probabilities indicated a 50-90% chance of 1 inch of rain, 30-60% chance of 2 inches and a 10-30% chance of 3 inches. The greatest risk of heavy rain and flooding will continue for the remainder of the afternoon into early this evening. Rainfall rates in the heavier showers and storms could be as high as 1 to 3 inches per hour, resulting in urban street flooding and ponding of water on area roads while creeks and ditches may rise rapidly. Fishermen and boaters on rivers should anticipate river rises and faster flows from runoff Thursday and Friday. On the backside of the vortex, gusty northerly winds and building waves will result in hazardous conditions for small craft into Thursday morning. Also, low stratus is expected tonight, combined with northerly winds should keep any dense fog away. The big change will be the cooler weather and much less humid conditions. Highs on Thursday will only be in the upper 60s to middle 70s. The dewpoints will continue on Friday and then will increase again over the weekend. The westerlies will linger along the U.S./Canadian border through the rest of the forecast period. This will result in an active period with periodic chances of showers/storms next week. The potential exists for stronger storms and heavy rainfall at times. The first round of storms arrive Friday night into Saturday morning with dry conditions expected Saturday night into Sunday night. The chances of showers and storms return Tuesday and Wednesday. Temperatures will be close to normal this weekend, then rise above normal for much of next week. && .AVIATION...for 06Z TAF Issuance Issued at 1113 PM CDT Wed Jul 16 2025 Lingering IFR/MVFR ceilings will continue tonight, along with some isolated to scattered light showers and sprinkles. Improvements in flying conditions expected Thursday morning. Clouds could linger a little longer than the models have due to the low-level moisture from the recent rain and/or add to the cu field during the day. Ceilings will rise to VFR by Thursday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Eckberg AVIATION.......Bersch