Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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352 FXUS63 KGRB 092332 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 632 PM CDT Tue Jul 9 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Small chances (30% or less) for showers and thunderstorms today through Thursday. The severe weather threat is very low. Locally heavy rainfall will be possible. - A warmer, and more humid, period develops for the weekend and early next week. Heat index values in the 90s are expected for much of the area by this weekend. && .DISCUSSION... Issued at 345 PM CDT Tue Jul 9 2024 Short Term...Tonight and Wednesday Focus is on small potential for showers and thunderstorms, along with fog and cloud trends. Satellite imagery at 19Z showed cu development across the Northwoods. There was some cu across central and east-central WI, but this was also inhibited by the cloud shield coming from the northern edge of Beryl remnants. Radar shows a few showers tried to get going in Forest and Florence counties within the last hour, but had trouble sustaining themselves. Rest of the afternoon and evening...Isolated showers and thunderstorms will be possible, mainly in northeast WI near the Upper Michigan border, which is what recent meso model runs have depicted. While there are some dynamics at play from a weak shortwave and RRQ of upper jet, instability is only 400 to 800 J/kg and shear is exceptionally low, with 0-3km shear of 5-10kts, and even 0-6km only around 10-20kts. Therefore, isolated showers and thunderstorms are possible, but severe storms are not likely. The main threat would be heavy rain as anything will be somewhat slow moving. Overnight...Patchy fog development is possible again. Winds will be light and there is still moisture near the ground from recent rains, but there will be more clouds tonight. Primary area to watch for fog is across the Northwoods where more cloud breaks are likely. Any fog would dissipate quickly after sunrise. Wednesday...Very similar to today, with highs in the upper 70s and low 80s, light winds, and a broken to overcast cloud layer. Could see some isolated showers or non-severe storms in the afternoon. The best chance is in central Wisconsin. Long Term...Wednesday Night Through Tuesday Main highlights from this forecast period revolve around small precipitation chances for Thursday, a better chance for this weekend, and the return of very warm and humid conditions late this week into this weekend. Precipitation...An embedded shortwave will phase with the main mid- level trough focused over the western Great Lakes region late Wednesday into Thursday. With little upper-level forcing present, anticipate diurnally driven isolated showers and non-severe thunderstorms to develop Thursday afternoon; however, most locations are likely to stay dry. The departed trough will be replaced with brief ridging, leading to dry conditions on Friday. Southwesterly flow will set up for the weekend and coincide with a series of shortwaves. Chances for showers and thunderstorms are anticipate throughout the weekend as a result, with the best chances occurring during the afternoon and evening when instability is peaking. Temperatures...A gradual warm up is expected from Thursday through the weekend due to the southwesterly flow lifting warmer, moist air into the region. NBM probabilities favor temperatures to peak on Sunday and Monday with probs for greater than 90 degrees in the 10- 20% range, with a few spots around 25%. While these temperatures are very warm, any showers or thunderstorms would cause lower values. In addition to the very warm temps, afternoon dew points will be in the upper 60s to low 70s, resulting in humid conditions and elevated heat indices (pushing the mid 90s on Sunday). Signs are pointing to little recovery occurring overnight throughout the weekend and into early next week as well, with lows in the 60s to low 70s. Will continue to monitor how temperatures may fluctuate over the coming days, but would recommend making adjustments to any outdoor weekend activities to cater to the heat. && .AVIATION...for 00Z TAF Issuance Issued at 632 PM CDT Tue Jul 9 2024 VFR conditions are expected through Wednesday, with a high overcast on the northern fringe of former hurricane Beryl. Ground fog is possible in far northcentral Wisconsin late tonight where there is less high clouds. Some scattered cumulus clouds are possible below the high overcast Tuesday. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....KLJ/Kruk AVIATION.......RDM