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Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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312 FXUS63 KGRB 112354 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 654 PM CDT Sun Aug 11 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Showers and a few scattered, non-severe thunderstorms are possible (15% to 25% chance) this evening, tomorrow and Tuesday afternoon/evenings, mainly in northern WI. - Widespread precipitation becoming likely (40 to 60% chance) Thursday into Saturday, but low confidence on exact timing and magnitude of precipitation at this time. Heavy Rainfall cannot be ruled out during this period. && .DISCUSSION... Issued at 259 PM CDT Sun Aug 11 2024 Our weather pattern will be fairly for the next few days. Similar to yesterday (Saturday) afternoon, widespread cu/sc establishes itself across northern/north-central WI under WNW flow. Scattered pockets of 850 moisture flux convergence phased with pockets of 950mb frontogenetical forcing will be a sufficient catalyst for a few of these SC/CU clouds to grow tall enough to produce a few scattered showers. With a few hundred joules of CAPE available during peak daytime heating, a few rumbles of thunder are possible. However, the severe weather parameter space is not supportive of severe weather at this time. Temperature-wise, highs for the next few days should be within a few degrees of normal for this time of year, with lows around 50 degrees, and highs in the upper 70s. Heading into the Thursday - Saturday timeperiod, a nearly vertically- stacked low is slated to establish itself near NE Iowa/SW Minnesota. Overall progression with this system is slated to move very slowly. The instability and shear parameter space doesn`t reflect anything notable for severe potential with this setup, so focus will be on locally heavy rains, especially given the slow movement of this system. The GFS ensemble runs have been much more bullish with this system than the ECMWF. Overall, the GFS family does seem slightly more plausible, so will initially lean some more towards it. If the GFS pans out, am at least slightly concerned about the potential for heavy rainfall. PWATs approach 2 inches, and the forecast vertical sounding profile looks to suggest efficient rainfall... as supported by 0-6 km mixing ratios of 8 g/kg & a wide swath of warm cloud depths 4.0-4.5km at times.. Even the less- bullish EC ensemble moisture parameters are anomalously high based on mid August climatology with 925/850mb specific humidities and precipitable water values in the upper 90th percentiles. && .AVIATION...for 00Z TAF Issuance Issued at 653 PM CDT Sun Aug 11 2024 Scattered light showers over central Wisconsin should dissipate this evening after sunset. Otherwise, VFR conditions are expected tonight and Monday. There is a slight chance of showers again late Monday afternoon and early evening in central and east central Wisconsin. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kotenberg AVIATION.......RDM