766 FXUS63 KGRB 281134 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 634 AM CDT Thu May 28 2020 Updated aviation portion for 12Z TAF issuance .SHORT TERM...Today...Tonight...and Friday Issued at 258 AM CDT Thu May 28 2020 Main forecast concerns through the short-term portion of the forecast will be one more muggy day across northeast Wisconsin along with widespread showers and thunderstorms. Some of the showers and storm will produce heavy rainfall. Today: A cold front is expected to shift from central/north-central WI this morning to the Lake Michigan shoreline around 18Z-21Z/28 as an area of low pressure lifts northeastward along the front. The slow movement of the front, along with a continued very moist airmass ahead of the front, will lead to heavy rain potential across the area. Some training is expected along and ahead of the front as the individual showers/storms lift from southwest to northeast, while the overall line of precipitation shifts slowly to the east. One thing that may pull back on the overall totals will be a secondary cold front that catches up with the slower moving front and helps to push it east a bit quicker. Still, it wouldn't be out of the question to see several places pick up an inch or more of rain by the time the front shifts east of the area late this afternoon into early this evening. Instability values are expected to be limited to around 500-1000 J/kg at best, which will be plenty for continuing the thunder mention. The better shear is expected to lag behind the front, so severe weather is not anticipated. The shear vectors are aligned parallel to the front, which again points toward heavy rainfall potential. Precipitable water values are running around 100-200 percent of normal for this time of year, generally in the 1 to 2 inch range. The combination of these features has led to WPC highlighting a good portion of northeast Wisconsin in a slight risk of excessive rainfall. Tonight: The cold front is expected to continue shifting eastward this evening, although some rain showers will likely linger along the Lake Michigan shoreline early in the evening. Behind the front, drier air will push into the area from the west, allowing the precipitation to come to an end. Aloft, an upper-level trough axis will slide across the area late tonight which will likely increase cloud cover once again, mainly over central WI. No precipitation is expected out of the feature during the overnight hours. Low temperatures will be cooler, with most locations dropping into the upper 40s to low 50s. Friday: As the aforementioned trough axis/shortwave passes through the area during the day, expect some late morning/afternoon instability showers/sprinkles to develop across northern portions of the area. Otherwise, temperatures are expected to be be cooler and humidity levels more comfortable across the area under partly cloudy skies. Highs are expected to be in the 60s to around 70 for most locations. .LONG TERM...Friday Night Through Wednesday Issued at 258 AM CDT Thu May 28 2020 500mb ridge across the Rockies this weekend will bring a northwest flow pattern to the western Great Lakes region into early next week. This will result in temperatures running slightly below normal this weekend with low humidity. The pattern will flatten out later next week, resulting in temperatures warming to or above normal levels by the middle of next week. High pressure will remain in control Friday night. Did lower minimum temperatures a few degrees based on the latest numerical guidance. After the recent warm spell, it will feel cool with lows in the middle 40s to around 50. On Saturday, dry conditions are anticipated at this time with highs in the upper 60s to lower 70s, cooler lakeside. Some of the models do depict light precipitation amounts along a surface boundary dropping across the area. Per coordination with NWS Green Bay, will leave this period dry for now. Dry condiitons are expected Saturday night through Sunday night. Did lower minimum temperatures a degree or two Saturday night. The next chance of showers and thunderstorms will arrive Monday or Monday night and continue into Tuesday as a warm front lifts northward and a cold front swings across the area. Low confidence in the rain chances next Wednesday. && .AVIATION...for 12Z TAF Issuance Issued at 633 AM CDT Thu May 28 2020 A cold front will move across the area from west to east throughout the day. MVFR/VFR conditions can be expected at each of the TAF sites, with occasional IFR conditions as heavier rain passes through each of the TAF sites. The worst condition are expected across the western TAF sites through about 18Z and over the eastern TAF sites through about 22Z. Clearing skies and improving conditions can be expected overnight. Scattered afternoon clouds along with some sprinkles will arrive Friday afternoon. && .MARINE... Issued at 258 AM CDT Thu May 28 2020 Areas of dense fog will continue into this afternoon. Extended the marine dense fog advisory until 4 pm this afternoon. Showers and thunderstorms will become more widespread this morning and continue this afternoon. The locally heavy rain may cause the fog to rise above one mile. The showers and storms will end tonight as the system moves away from the area. Weak high pressure will move into the region Friday and continue over the weekend, bringing mainly dry conditions. && .HYDROLOGY... Issued at 258 AM CDT Thu May 28 2020 A slow moving cold front, passing through the area today, will lead to widespread rainfall totals of 1-2 inches. Hi-RES models continue to show an area of heavier rainfall totals/rates across portions of central Wisconsin this morning, with localized 3 inch totals possible. This heavy rainfall may lead to localized flooding across portions of central Wisconsin early today, before the cold front begins to shift eastward. Additional, localized flooding may occur across the rest of northeast Wisconsin as the front traverses the area later this morning into this afternoon. Higher flows on area rivers can be expected today into tonight. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....Cooley LONG TERM......Kallas AVIATION.......Cooley MARINE.........Kallas HYDROLOGY......Cooley