Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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106 FXUS63 KGRB 251749 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1249 PM CDT Sat May 25 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Memorial Day weekend starts off dry for today, but rain chances increase by late Sunday morning and continue into Memorial Day. A soaking rain could occur during this time. - A few rivers over central and eastern Wisconsin could surpass minor flood stage early next week. - Below normal temperatures area expected for the first half of next week. Patchy frost is possible Thursday morning over parts of northern Wisconsin. && .DISCUSSION... Issued at 449 AM CDT Sat May 25 2024 Short Term...Today...Tonight...and Sunday Skies will continue to clear from west to east early this morning as a ridge of high pressure builds in across the western Great Lakes region. Mostly sunny skies and breezy conditions are expected today as winds shift from west to southwest throughout the day. An isolated shower is possible in north-central Wisconsin late this afternoon as a weak shortwave rotates around an upper low located across southern Canada. Highs today are expected to range from around 70 across the north, to the lower 70s across the rest of the region away from Lake Michigan. Surface winds will turn south-southeast tonight as the area will be in between the departing ridge of high pressure to the east and a low approaching from the southwest. Despite mostly clear skies, some modest warm air advection will keep temperature relatively warm tonight as low temperatures only fall into the lower to middle 50s. A surface low tracking through the mid Mississippi Valley with an attendant mid level negatively tilted trough and PV anomaly tracking through the southwestern Great Lakes will bring precipitation back to the area for Sunday. Rain will spread in across central Wisconsin early Sunday morning, then across the rest of the area late Sunday morning into early Sunday afternoon. While this system will bring a slug of significant moisture and decent dynamics through Wisconsin, instability will be lacking as MUCAPEs only rise to a few hundred J/kg Sunday afternoon. This meager instability will mean only isolated thunderstorms are expected across central and east-central Wisconsin Sunday afternoon, with the severe threat staying well to our south. Although PWATs are only expected to be 0.5 to 0.75 inches, the steady rain for much of the day could add up to 0.5 to 1 inch during the day on Sunday. Highs on Sunday are only expected to rise into the 60s with the steady rain showers for much of the day. Long Term...Sunday Night Through Friday A progressive mean flow across the CONUS will bring two more shortwave troughs through the Great Lakes early next week. This flow becomes more amplified toward mid-week with upper troughs over both coasts and an upper ridge over the central CONUS. This upper ridge should bring dry conditions to northeast WI for the end of the forecast period. Temperatures will run at or below normal through mid-week, then warm slightly above normal by late next week. Sunday night and Memorial Day... Showers/thunderstorms to be ongoing at the start of the period as a mid-level shortwave trough to be moving through the region. Stronger storms would appear to remain to our south where a surface low sliding toward southern sections of the Great Lakes will be accompanied by a cold front. Locally heavy rain is still possible during the evening as PW values to be 1.25-1.50" and northeast WI to reside in the right entrance region of the upper jet. Precipitation should trend down overnight across central WI as the shortwave trough begins to exit the area. Min temperatures to be in the middle 40s to lower 50s. The forecast for Memorial Day remains tenuous as the models are having timing issues between how fast the initial system departs and the approach of another shortwave trough in the afternoon. The NAM and CMC are slower with the exit of the first system, thus there is not much of a break in the rain chances. Conversely, the GFS and ECMWF are faster with the exit of system one, thus at least the morning of Memorial Day would be dry. For now, have kept a minimal pop for the morning hours and keep chance pops for the afternoon. Max temperatures to mainly be in the middle to upper 60s (slightly cooler near Lake MI). Monday night and Tuesday... Spotty rain chances would continue into Monday night, but this shortwave trough is rather weak and with no surface features evident, any precipitation would be very light. Otherwise, partly to mostly cloudy skies can be expected with min temperatures to range from the lower to middle 40s north-central WI, upper 40s to around 50 degrees east-central WI. Yet another (and stronger) shortwave trough quickly dives southeast into the Great Lakes on Tuesday and bring another chance of showers/thunderstorms to northeast WI. Shear is forecast to be very weak (25 kts or less), thus severe potential looks to be very low. More clouds and precipitation chances will temperatures below normal with lower 60s north-central, middle to upper 60s elsewhere. Tuesday night and Wednesday... A few showers could linger over east-central WI early Tuesday evening as the shortwave trough still in the process of exiting the area. Otherwise, a gradual decrease in clouds are expected for Tuesday night as high pressure starts to build over the Upper MS Valley. Mostly sunny skies are forecast on Wednesday as the high pressure settles over the western Great Lakes. A northerly wind will keep temperatures a little below normal with readings in the lower to middle 60s near Lake MI, middle 60s to around 70 degrees inland. Wednesday night and Thursday... Clear skies and nearly calm winds will allow temperatures to quickly fall Wednesday night, thus may have to watch for potential frost over northern WI. As the high pressure drifts toward the eastern Great Lakes on Thursday, winds will shift to the south and pull warmer air back into WI. Expect max temperatures on Thursday to be in the middle to upper 60s near Lake MI, lower to middle 70s inland. Thursday night and Friday... As the mean flow becomes more amplified with time, systems to slow their eastward movement. Therefore, the high pressure to remain parked over the eastern Great Lakes through Friday and with the upper ridge overhead, anticipate dry conditions to persist. Prevailing south-southwest winds will continue to bring warmer air into northeast WI as max temperatures Friday climb to around 70 degrees lakeside, middle to upper 70s inland. && .AVIATION...for 18Z TAF Issuance Issued at 1249 PM CDT Sat May 25 2024 VFR flight conditions will continue through Sunday morning. Skies will be mostly clear today, with increasing middle and high clouds overnight. A low pressure system, moving from Kansas to Lower Michigan will bring showers and a few thunderstorms Sunday afternoon through Sunday night. The thunderstorms should be generally south of a CWA to GRB line. FLight conditions will be mostly MVFR Sunday afternoon, and IFR Sunday night. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kurimski/Kallas AVIATION.......RDM