Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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086 FXUS63 KGRB 120351 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1051 PM CDT Tue Jun 11 2024 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Periods of light rain are expected through this evening. A thunderstorm is possible, but no severe weather is anticipated. - There is a Marginal Risk of severe thunderstorms late Wednesday afternoon and Wednesday evening when one or more complexes of storms could impact the region. The latest indications suggest locations over central Wisconsin have the highest chance of seeing strong storms, which may contain gusty winds and hail. Confidence is low where these thunderstorms will track. - Well above normal temperatures are forecast from Sunday into the middle of next week. Heat indices may surpass 90 degrees at times. && .DISCUSSION... Issued at 232 PM CDT Tue Jun 11 2024 Short Term...Tonight and Wednesday The latest RAP analysis and satellite/radar imagery show a cold front moving across the northern Mississippi Valley with help from a modestly potent shortwave trough. A broken band of rain along the leading edge of a warm advection zone is proceeding east at about 30 kts across central Wisconsin. This band of showers will likely weaken somewhat, but not enough to dissipate before reaching eastern WI. The trailing cold front has been inactive so far today, but convective clouds are building along the boundary. Between this system and the next system arriving on Wednesday, precip and severe weather chances are the focus of this forecast. Precip Trends: Behind the light band of rain showers, the convective allowing models indicate that additional showers may redevelop later this afternoon. No thunderstorms are expected. Right along the front, a few thunderstorms could develop early this evening along a narrow ribbon of 600-800 j/kg cape. If thunderstorms develop, central WI will have the greatest chance. Brief gusty winds will be possible through the evening if storms develop. Then quiet conditions return overnight. Then within fast, zonal flow aloft, light showers could develop over north-central and far northeast WI in the afternoon. But all eyes will be on southeast Minnesota and northern Iowa for strong thunderstorm development along the instability gradient in the afternoon. Some storms could make a run at central Wisconsin after 5 pm. Severe weather chances: Within a region of strong instability (2000-3000 j/kg mixed layer cape), strong to severe thunderstorms are forecast to develop over central Minnesota around 1-2 pm. These thunderstorms are forecast to grow upscale into a complex and track along the cape gradient on the nose of the 35-45 kt low level jet to the southeast and into southwest Wisconsin by late in the afternoon. While tracks and timings may still change, the latest guidance suggest central WI will be on the northern edge of any convective complex. Some guidance shows instability upwards of 1500 j/kg sneaking into Wood, Portage, and Waushara counties where a severe wind/hail threat may develop by 22-23z. If it comes to fruition, the strong to severe thunderstorm threat should end relatively early on Wednesday night due to fast forward motion of the complex, perhaps around the 10 to 11 pm time frame. Chances appear lower than previous forecasts over north-central WI where another complex could develop over the Arrowhead of Minnesota before tracking east into Lake Superior. Long Term...Wednesday Night Through Tuesday The main focus of the extended forecast will be on the evolution of the 500mb pattern through the end of the week, which may bring both our next round of strong active weather and well above normal high temperatures. Active weather underway from late Wednesday afternoon will rapidly push through the region during the evening hours, departing by the early overnight hours. The strongest storms may yet move through portions of central Wisconsin, but general consensus still brings the strongest storms south of the area. See the short term discussion for additional information. The cold front that brought the active weather through on Wednesday is expected to drop well south of the area Thursday, bringing back quiet conditions for our area. Any redevelopment along the cold front will stay south, impacting primarily northern Illinois and southern Wisconsin. As high pressure begins to depart Saturday, southerly return flow will begin to ramp up. A strong push of warm moist air will cross the region by late Saturday, bringing with it another chance for some active weather. Instability parameters due suggest some potential for stronger storms, so Saturday afternoon through Sunday will be a time period to watch for severe potential. Behind this, the area is expected to be well in to the warm sector. Long range guidance still brings high temperatures well into the 80s both Sunday and Monday, with a chance for low 90s. These temperatures may still come down on Sunday depending on how quickly any precipitation and cloud cover pushes through from Saturday, but the warmup remains in the forecast. && .AVIATION...for 06Z TAF Issuance Issued at 1051 PM CDT Tue Jun 11 2024 Some isolated showers are possible across eastern Wisconsin around midnight as a cold front tracks through the rest of the region. Given the isolated nature of the activity, will only include a VCSH in the eastern TAF sites for the first few hour or two to account for these showers. Generally good flying weather is expected through Wednesday afternoon. By late in the afternoon or early evening, shower and thunderstorm chances will increase as a warm front lifts north across the western Great Lakes with attendant cold front pushing in Wednesday night. Current CAMs models are not clear on how widespread the activity will be across the area with some solutions splitting the storms to the north and south with our area not getting much in the way of showers or thunderstorms. Therefore, will only include a VCSH Wednesday night as there is a chance the area does not get much in the way of rainfall with this system. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....MPC/Uhlmann AVIATION.......Kurimski