Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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492 FXUS63 KGRB 011145 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 645 AM CDT Sat Jun 1 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Scattered showers into early this evening. Best chances for non- severe storms (30-40 percent) north-central to central WI this afternoon into early this evening. - Rain and storms are possible Monday afternoon. While storms aren`t expected to be severe, an isolated strong gust up to 35 to 40 mph with any storms is still possible. - A better chance for strong storms arrives later in the day Tuesday. These storms may also be accompanied by heavy rainfall. && .DISCUSSION... Issued at 355 AM CDT Sat Jun 1 2024 Short Term...Today...Tonight...and Sunday Coverage and location of shower and thunder chances today is the main focus. Shower chances today and fog potential tonight: Radar loop early this morning shows showers have shifted north and west of even north-central WI closer to narrow ribbon on higher PWATs and close to weakening cold front/moisture boundary. This boundary will shift slowly east today so some showers will spread back into central and north-central WI this morning. Instability limited so have scaled back on any thunder mention through mid morning. Later this morning into the afternoon seems when most of cwa will have the greatest chances for some showers, still very scattered in nature though. This will be as the boundary upstream shifts across in response to shortwave trough sliding east into northwest Ontario and also as the southeast area is on fringe of southern stream system lifting across the Ohio Valley. Best chance for thunder is this afternoon from north-central to central WI with weak instability pooling along what will mainly be low-level wind shift, mainly noted at H85. Showers end early this evening. Nighttime cooling and a moist boundary layer could lead to some fog late evening and overnight. Capped this at patchy coverage now, but some more widespread fog is possible where rain is more persistent today. Once the fog diminishes after daybreak on Sunday, other than some diurnal cu, conditions will remain dry into Sunday afternoon as bubble of high pressure slides across the area. Temperatures: After a mild start early this morning, expect highs today to reach at least the low 70s with greatest chance of mid 70s from southwest cwa into far northeast WI where rain is least likely into the afternoon. High pressure across the area tonight will promote temps falling back into the upper 40s north and in the mid 50s elsewhere. Cu and a weak lake breeze will be the only thing to put breaks on temps on Sunday. Mixing to H75 inland supports highs eclipsing 80 most everywhere with even some lower 80s possible. Coolest readings around 70 will be right along the Lake Michigan shore. Long Term...Sunday Night Through Friday The main focus for the extended forecast will be on Monday and Tuesday, both of which could have a round of active weather and storms. Sunday night and Monday... Ensemble guidance brings a surface low northwest of the region overnight through Monday morning. A northward surge of warm air will likely bring some rain into the region by the mid morning, ahead of a strong upper shortwave that will help sustain and spread eastwards a round of showers and storms. The timing of this shortwave will not favor severe weather however, as instability in the region will be fairly scarce without a chance to warm up. Additionally, the cold front previous forecasts focused on for redevelopment has become less defined due to the more northerly track of the surface low. Therefore severe weather later on Monday isn`t favored either. All that said, any isolated storms that do form in the region could still bring a few stronger gusts, mixing down some of the 30-40 knot winds around 925mb and 850mb. Tuesday... Attention then turns to the next system as another strong shortwave crosses northern CONUS and southern Canada. This will be a fairly strong and dynamic system, bringing a surge of warmth and moisture into the region before the trailing cold front arrives. With dewpoints pushing into the lower 60s, surface instability will be fairly high for this event. Timing remains uncertain, ranging from Tuesday evening to the overnight hours, which in turn brings uncertainty into the overall severe potential as instability will start to wane overnight. That said, the dynamics of this system remain impressive so this time period will bear watching going forward. Rest of the forecast... Guidance suggests that the low mentioned for Tuesday may occlude north of the region around the middle of the week, separating from the mean flow and bringing additional, lighter rounds of precipitation in the region to round out the week. This will also bring some milder temperatures back to the area, with highs falling back into the middle 60s to lower 70s for the middle to end of the work week. && .AVIATION...for 12Z TAF Issuance Issued at 644 AM CDT Sat Jun 1 2024 A weakening cold front and a separate system tracking from the middle mississippi river valley across the Ohio Valley will combine to bring scattered showers to the region today. The greatest chances for steady showers will be this morning at RHI, AUW and CWA, then late this morning into mid afternoon at MTW. Conditions a mix of MVFR to low-end VFR. As the cold front shifts eastward this afternoon, a secondary line of scattered showers and isolated storms may form from north-central to central WI. Greatest risk of thunder will be at RHI. Once any lingering showers end early tonight, nighttime cooling, light winds and partial clearing will open the door to some fog late this evening through the overnight hours. At least MVFR vsby expected at most terminals. IFR possible at MTW where fog may have added moisture off Lake Michigan and also from central to north- central WI where rain is most prevalent today. On Sunday, after any fog dissipates early, plan on VFR flying conditions at all the terminals. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....JLA/Uhlmann AVIATION.......JLA