Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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856 FXUS63 KGRB 091744 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1244 PM CDT Thu May 9 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - An unsettled weather pattern will bring intermittent chances of showers and a few thunderstorms through the weekend. Severe weather is not expected with any of these thunderstorms, but we will be watching for the potential for strong storms on Sunday. - Low temperatures in the lower to middle 30s will be conducive for a frost or freeze over north-central and far northeast Wisconsin late tonight into early Friday morning. - Due to rainfall over the past week, river levels remain elevated. Some rivers may reach or surpass bankfull. && .DISCUSSION... Issued at 335 AM CDT Thu May 9 2024 Short Term...Today...Tonight...and Friday Forecast concerns include minor precipitation chances today, frost/freeze potential over northern WI tonight, and another round of showers and thunderstorms arriving Friday afternoon. A weak frontal boundary and short-wave trough was generating a band of scattered light showers across far northern WI early this morning. These showers were drifting slowly south and gradually weakening. Farther south, showers associated with a short-wave over northern IA were edging toward the sw part of the forecast area. The weak cold front will continue to sag south and eventually interact with the IA short-wave as it moves east through southern WI. This should bring a small chance of showers over the far southern part of the forecast area today. Highs should reach the upper 50s to lower 60s, except middle 50s near lake Michigan. Brisk NE winds will occur in the Fox Valley. Any showers should shift south of the region by evening, followed by clearing skies as a ridge of high pressure moves into WI. Light winds will allow temperatures to drop into the upper 20s to middle 30s north, and upper 30s to lower 40s south. Areas of frost and localized freezing temperatures will likely occur over north central and far northeast WI. Frost/freeze headlines look like a good bet, but will let the day shift make headline decisions this afternoon. On Friday, morning sunshine will give way to increasing clouds and showers as a cold front and potent short-wave trough arrive in the afternoon. Will keep eastern WI dry until the evening, but have increased pops to likely over north central and central WI late in the day. Most of the SBCAPE is expected to remain west of the forecast area, but mid-level lapse rates of 7.0-7.5 C/km support a mention of thunderstorms. Highs should reach the lower 60s northwest, and middle to upper 60s elsewhere, except near Lake Michigan, where temperatures will only reach 55 to 60 degrees. Long Term...Friday Night Through Wednesday The forecast continues to call for low impact weather for the next week as the region will be under northwest flow through next Monday. Forecast concerns mainly revolve around light rain and thunderstorm chances. Rain and thunder chances...A dynamic shortwave will bring light rain to the region on Friday night. Minor instability up to 300 J/kg of most unstable cape is still projected to sneak into central and north-central WI in the evening that could lead to a slight chance of a thunderstorm. Otherwise, precipitation amounts of a 0.10-0.25" remain possible before precip exits late on Friday night. In the wake of this shortwave, a trailing shortwave will interact with diurnal instability to produce cloud cover and possibly a few showers. 0-3 km lapse rates are relatively steep to 8.5 C/km, but equilibrium levels are quite low at around 650 mb and not sufficient for thunderstorm development. Will keep precip chances low. Most precip will dissipate with loss of heating by early Saturday evening. Another chance of precip remains projected to arrive on Sunday into Sunday evening when a warm front, followed by a cold front, move across the region from the northwest. Despite weaker dynamics compared to the Friday night system, instability looks considerably more robust with mixed layer capes from 700-1000 j/kg over central and north-central WI. Thunderstorms look possible, but the severe threat appears low due to weak deep layer of 20 to 25 kts. After this system, the chance of rain looks to return during the middle of next week. Temperatures...High temperatures in the 60s and 70s are forecast from Saturday through the middle of next week. There was some concern for frost on Saturday night, but cloud cover looks to arrive earlier ahead of the Sunday system which will mitigate the chance of frost. Low temperatures have therefore increased on Saturday night. && .AVIATION...for 18Z TAF Issuance Issued at 1244 PM CDT Thu May 9 2024 VFR conditions are expected through at least midday Friday. Clouds will clear from north to south tonight, with clouds remaining longest over central Wisconsin. An approaching cold front will bring MVFR conditions, showers and scattered thunderstorms west of an Iron Mountain to Wisconsin Dells line Friday afternoon, and further east Friday evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch/MPC AVIATION.......RDM