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Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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553 FXUS63 KGRB 122347 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 647 PM CDT Mon Aug 12 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Isolated to scattered showers and storms (20% to 30% chance) will continue for the rest of the afternoon and early this evening, and then again Tuesday afternoon/early evening. Severe thunderstorms are not expected. - Showers and some thunderstorms likely (50 to 80% chance) Thursday into Friday. Severe potential remains low, but locally heavy rain could occur. Small chances of rain (20-40 percent) this weekend. - Conditions hazardous to small craft possible on Lake Michigan Thursday and Thursday night. && .DISCUSSION... Issued at 225 PM CDT Mon Aug 12 2024 Short Term...Tonight and Tuesday As of 2 pm, isolated showers and perhaps a thunderstorms developed across Shawano and Marathon counties. The showers/storms were sagging slowly south-southeast at less than 10 mph. Under partly sunny skies, temperatures warmed into the middle 70s to lower 80s. Isolated showers and storms will continue for the rest of the afternoon into early this evening. Some of the showers and storms could produce a brief period of heavy rain. Severe storms are not expected. The rain should end by mid evening, otherwise skies will be clear to partly cloudy. Lows tonight should drop into the lower to middle 50s north to around 60 south and along the bay and Lake Michigan. A repeat performance is expected Tuesday afternoon into the early evening hours. The cumulus field is expected to develop during the late morning into the early afternoon. Bufkit soundings indicated 500 to 1,000 J/KG of CAPE to support the mention of thunder. High temperatures should climb into the upper 70s to middle 80s. Long Term...Tuesday Night Through Monday Some lingering instability showers will quickly want Tuesday evening with the loss of daytime heating. Otherwise, high pressure settling in across the central Great Lakes will keep the forecast dry for the middle of the week as temperatures inch to a few degrees above normal for this time of year. A low pressure system will organize across the Plains during the middle of the week and slowly make its way east towards the upper Mississippi Valley Thursday and the western Great Lakes Thursday night. The system itself will have strong dynamics and abundant moisture, as evidenced by PWATs of 1.5 to 1.75 which is the 90th percentile for this time of year, along with modest instability. This should lend itself to steady rain during this period with occasional heavy rain and isolated thunderstorms. QPF amounts during this period will likely be 1 to 2 inches, with locally higher amounts possible. The low looks to linger across the region on Friday, then track east of the region sometime this weekend. The key to how long the low hangs around the region will be if it becomes cut-off across the central Great Lakes or is more of an open wave. Even if the low becomes cut-off, the heaviest rain should be over by the weekend as the best instability and dynamics will have waned by then. && .AVIATION...for 00Z TAF Issuance Issued at 646 PM CDT Mon Aug 12 2024 A nearly stationary front from DLH to AUW to MTW was producing scattered showers and thunderstorms again this afternoon. They should gradually dissipate during the evening after sunset. VFR conditions and mostly clear skies are expected elsewhere. Patchy ground fog is likely again late tonight through 13z Tues. Skies should start out clear Tuesday, but clouds with bases of 4000 to 6000 feet should form by midday. There could be scattered showers or thunderstorms in the later afternoon and evening from roughly RHI to GRB. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Eckberg/Kurimski AVIATION.......RDM