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Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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689 FXUS63 KGRB 152347 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 647 PM CDT Mon Jul 15 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Isolated to scattered storms this evening. Some storms could be severe. Primary hazards are damaging winds and brief, but heavy, downpours. - Mainly dry weather expected mid-late week into next weekend. Some small rain chances, but no widespread rain and severe weather is not expected. - Not as warm and less humid on Tuesday. Temps drop below normal Wednesday, but are back around normal late this week into this weekend. && .DISCUSSION... Issued at 212 PM CDT Mon Jul 15 2024 Short Term...Tonight and Tuesday Main forecast concerns will once again revolve around severe weather potential for this afternoon and evening. Most likely scenario shows isolated to scattered storms firing off along the cold front during the mid to late afternoon, although there is still some uncertainty with storm evolution later in the evening. Convective trends/severe potential... Expect early to mid afternoon to remain mostly dry as an MCS tracks from southern Minnesota across southern Wisconsin. Attention then turns to storm potential later this afternoon and evening as a robust cold front sweeps across the forecast area. CAMs are still showing several different scenarios for how convection will pan out. Cloud debris combined with lingering precip from the aforementioned MCS may act to hinder surface heating across central Wisconsin during the day before additional cloud cover builds in ahead of the cold front. This being said, low-level moisture (dewpoints in the low 70s) and resultant instability (3,000+ J/kg CAPE) would certainly be enough to generate at least some discrete storms. As SRH (0-1 km SRH ~100 to 150) and deep layer shear (45 to 50 knots) increase ahead of the front, it wouldn`t take a lot for any of these cells to start rotating. Hence, a brief spin-up would not be completely out of the question if convective elements are able to organize. Primary threats will be gusty winds, hail, and locally heavy rain as evidenced by inverted-V soundings, steep mid-level lapse rates, and high PWATs. Suspect that widespread flooding concerns will be kept at bay due to progressive storm motion. Main flooding concern would result from training storms over the same area. Limiting factors to storm development center around high convective temperatures during the afternoon and coincident LCL heights (above 1,000 feet) limiting storm coverage. Regardless, current thinking is that isolated to scattered storms will ignite along the cold front from north to south given frontal strength, time of day, and pre- frontal unstable airmass. Smoke trends... Models/satellite observations continue to show a plume of near surface smoke skimming northern Wisconsin as a thin layer of elevated smoke builds in from the west. Will continue to monitor for air quality concerns and visibility reductions through tomorrow as low-level smoke spreads across northern Lake Michigan. Have thus opted to retain haze in the forecast through tomorrow morning. Tuesday... Models are picking up on scattered shower activity tomorrow afternoon and evening as a shortwave dives down from Ontario and into the Great Lakes region. Not expecting anything strong to severe as large-scale subsidence behind the front will place weak high pressure over the upper Midwest. Long Term...Tuesday Night Through Monday There will be some rain chances, but overall the pattern will turn drier than it has been lately. Axis of mid-level trough that is bringing the strong cold front across today will cross the upper Great Lakes on Wednesday. A few showers possible Tuesday night and more so on Wednesday as the trough approaches and then crosses. High pressure builds in Thursday and Friday, leading to period of dry weather. Temperatures will be seasonably cool on Wednesday then trend toward normal late this week. Looking ahead to the weekend and beyond, there will be some small chances of mainly afternoon pop-up showers and maybe a storm, but no widespread rain or severe weather is expected. Temperatures will end up around normal with highs mainly in the lower 80s. && .AVIATION...for 00Z TAF Issuance Issued at 647 PM CDT Mon Jul 15 2024 Scattered showers and thunderstorms are possible this evening as a cold front moves across the region. Outside of any convection, VFR conditions are expected. Some clearing is possible late tonight and Tuesday morning, but high based cumulus clouds will form in the afternoon, with isolated showers or thunderstorms possible. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Goodin/JLA AVIATION.......RDM