Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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309 FXUS63 KGRB 090258 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 958 PM CDT Mon Jul 8 2024 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Areas of dense ground fog are possible late tonight and early Tuesday morning, especially in central and north central Wisconsin. - On and off chances for showers and thunderstorms will continue Tuesday through Thursday. Although the severe weather threat remains low, locally heavy rainfall will be possible. - Some rivers, creeks, and streams across east-central Wisconsin will continue to run above bankfull due to recent rainfall. - A warmer/drier period may be in store toward the end of the week and into the weekend. && .DISCUSSION... Issued at 248 PM CDT Mon Jul 8 2024 Short Term...Tonight and Tuesday Precipitation/thunderstorm trends are the main forecast concern, along with the potential for fog later tonight. The MCV that brought heavy rain to parts of northeast WI has shifted out of the region, but additional thunderstorm development was occurring. A small cluster of storms was moving into the Fox Valley, and more numerous showers and storms were forming in NC WI, in association with a short-wave trough and weak surface boundary. The stronger storms were producing torrential downpours, brief gusty winds and small hail, in an environment characterized by SBCAPE of 1200-1800 j/kg and modest deep layer shear around 25-30 kts. Kept the highest pops in NC WI through the afternoon, with lower chance pops farther southeast. The overall activity should wane as the short-wave shifts east and daytime instability decreases this evening. Partial clearing, lingering low-level moisture from recent heavy rain and light winds should lead to patchy/areas of fog later this evening and into the overnight. The fog should be most extensive in the climatologically-favored Wisconsin River Valley (NC/C WI), but will mention at least patchy fog over the entire CWA. Lows tonioght should range from the lower to middle 50 northwest to the lower 60s southeast. After a dry period late tonight into Tuesday morning, increasing afternoon instability should lead to isolated/scattered thunderstorms. The best chance of storms should occur in the favored convergence area over far NE WI, where a weak short-wave and the RRQ of an upper jet will also reside. Not expecting any severe weather, as SBCAPE of 500-1000 j/kg and deep-layer shear of 15 to 20 kts is not too impressive. High temperatures should reach the upper 70s to middle 80s. Long Term...Tuesday Night Through Monday Although the remnants of Beryl are forecast to miss us well to the southeast, a mid level PV anomaly combined with SBCAPEs around 1000 J/kg could generate scattered showers and thunderstorms across the area on Wednesday. Bulk shear values on Wednesday will be fairly weak, only 20 knots, so severe thunderstorms are not expected. Another round of isolated showers and thunderstorms is possible Thursday afternoon with SBCAPEs of 1000 to 1500 J/kg and only 15 knots of bulk shear. However, forcing will be weaker than Wednesday so coverage is not expected to be as high. Dry weather is then expected to close out the week as high pressure builds in across the Great Lakes. As the high drifts east, it will allow warm temperatures to surge into the region from the south as dew points also increase. This will allow temperatures to soar well into the 80s this weekend into early next week, with a few 90s possible on Sunday and Monday. Dew points will surge into the 60s on Saturday and into the lower 70s on Sunday and Monday across portions of central and east- central Wisconsin. The combination of heat and humidity will cause heat index values to rise well into the 90s across central and east- central Wisconsin Sunday and Monday afternoon. In addition to the heat and humidity, shortwaves tracking along the periphery of the ridge will bring the chance for showers and thunderstorms back to the region from Saturday through next Monday. The best chances will be during the afternoon and evening hours when instability is maximized. && .AVIATION...for 06Z TAF Issuance Issued at 955 PM CDT Mon Jul 8 2024 Clearing skies, light winds and wet ground will make for areas of dense ground fog tonight. The area west of a IMT to AIG to STE line looks most likely to see dense ground fog. It is also possible at PCZ, Y50, ATW, OSH and to a lesser extent GRB. There may also be some fog near the Lake Michigan shore at MTW. Whatever ground fog forms overnight should dissipate by 13z Tuesday. Scattered to broken cumulus clouds with bases between 3500 and 5000 feet are expected during the late morning and afternoon hours. There is a slight chance that isolated showers or thunderstorms could from along lake breezes near the lake and bay during the afternoon. Any convective activity that forms should dissipate quickly Tuesday evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch/Kurimski AVIATION.......RDM