Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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535 FXUS63 KGRB 270353 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1053 PM CDT Sun May 26 2024 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 717 PM CDT Sun May 26 2024 Widespread moderate to locally heavy rainfall covered all but the far northwest part of the forecast area early this evening. To this point, the heaviest rainfall amounts have been reported over central WI, where 1-2 inches has already fallen. Think the heavy rainfall threat has diminished in C WI, so not expecting any major flooding concerns there, other than rising rivers. Farther east, some elevated instability is working its way into the southern Fox Valley, and should continue to spread northeast through the valley and lakeshore areas this evening. A potent negatively-tilted short-wave trough will also sweep through this area, generating thunderstorms with periods of torrential rainfall this evening. This, combined with the heavy rainfall that moved through an hour or two ago, may lead to some urban flooding. For now, we have issued a Special Weather Statement to highlight the concern, but we will be monitoring for potential urban flooding through the evening. && .KEY MESSAGES... - Showers will continue through late tonight. A few strong thunderstorms are possible in the Fox Valley and lakeshore areas through this evening. Around an inch of rain is expected across the area, with locally higher amounts approaching 2 inches possible. Flooding of streets and small streams will be possible, especially in the Fox Valley and lakeshore areas. - A few rivers across central and eastern Wisconsin could surpass minor flood stage early this week. - Areas of patchy frost are possible Wednesday night into early Thursday morning across far northern Wisconsin. && .DISCUSSION... Issued at 256 PM CDT Sun May 26 2024 Short Term...Tonight and Monday Showers and a few elevated thunderstorms will continue tonight as the surface low moves right across Wisconsin. Rainfall amounts of .10" to .20" an hour have been reported at 2pm with the bright band echoes (35 to 45 Dbz) over central Wisconsin. The heavier rain should move into Northeast Wisconsin this evening. An inch or two of rain could fall from central to northeast Wisconsin, with less to the east and west. This amount could produce some street flooding and maybe brief flooding of small streams. The rain from tonight will make it into the larger streams and rivers over the next day or two and will likely raise some of the levels to bankfull, or perhaps minor flood stage. The rain will likely end by daybreak across the lakeshore counties, but there will be a chance of showers and thunderstorms again in the afternoon as a weak short wave approaches. Highs will be a couple of degrees below normal. Long Term...Monday Night Through Sunday Focus for the extended remains on rain chances early in the week before the current pattern begins to quiet down mid-week. Lingering wrap-around precip on the back end of Sunday`s system is expected to be light. The remainder of the week then looks to be mostly dry as a high amplitude blocking pattern sets up across the CONUS. Next chances for precip are expected to arrive sometime over the weekend, although models are struggling to hone in on timing this far out in the forecast period. Monday evening through Tuesday precip chances... Following the passage of a weak shortwave on Monday, a more robust mid-level disturbance is expected to trail across the Great Lakes region early Tuesday. Synoptic support associated with Monday evening and Tuesday precip is lacking due to the absence of surface features or any convective elements. Thus, rain chances will be largely dependent on mid-level forcing associated with the shortwave. This being said, a rumble of thunder wouldn`t be out of the question across east-central Wisconsin Tuesday afternoon during peak heating. However, any thunderstorm activity would likely be short- lived as already minimal instability declines with the loss of daytime heating. There is still some model spread in exact rainfall amounts through Tuesday, although most locations should see between 0.1 to 0.2" of light rain. Locally higher amounts approaching 0.4" QPF may be possible across east-central Wisconsin, especially near the lakeshore. Rest of the extended... Rest of the week looks relatively quiet as an omega block centers itself over the CONUS. The combination of upper-level ridging and dominant high pressure at the surface will place most of the western Great Lakes under a south/southwest flow regime, advecting up a warmer airmass from the south. As a result, temperatures will gradually increase through the end of the week before plateauing in the low to mid 70s Friday through Sunday. Light winds and mostly clear skies may drop temperatures down into the low to mid 30s across the far north, will thus be monitoring potential for patchy frost. Next chances for precip then enter the forecast area either Friday or Saturday as return flow from departing high pressure tracks a plume of moisture across the upper Midwest. && .AVIATION...for 06Z TAF Issuance Issued at 1048 PM CDT Sun May 26 2024 Widespread moderate to locally heavy showers will slowly lift north through NE WI overnight, and exit by early Monday morning. Not sure if low clouds will fill in over NC WI overnight, but will hedge that direction due to guidance trends. Elsewhere, expect MVFR/IFR ceilings to persist into Monday morning before lifting to VFR in the early to mid afternoon. A short-wave trough will bring a chance of showers and storms to mainly the southwest part of the CWA Monday afternoon and early evening, but confidence is not high enough to mention storms at any of the TAF sites. LLWS will occur in parts of the CWA overnight. Gusty surface winds from the NE will back to the NW late tonight into Monday. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.........Kieckbusch DISCUSSION.....RDM/Goodin AVIATION.......Kieckbusch