269 FXUS63 KGRB 272020 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 320 PM CDT Sat Apr 27 2024 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Southwest winds could gust to 45 mph or more across central and east-central Wisconsin this afternoon. - It remains possible that conditions will support a few strong to severe storms late this afternoon into this evening across northeast Wisconsin, with the greatest risk of severe storms through 9 pm from the Fox Valley to the lakeshore. There is still a lot of uncertainty in the coverage of strong or severe storms. - Better chances for rain return Sunday morning and continue through Monday. Periods of moderate to heavy rain Sunday into Monday morning, could result in isolated flash flooding in urban and low lying areas. Rivers will be on the rise through the middle of next week, with a few of them reaching bankfull stage. - Conditions hazardous to small craft are expected this weekend on the Bay and Lake. A few gale force gusts are possible this afternoon, especially on the southern end of the bay and Lake Michigan south of Manitowoc. && .DISCUSSION... Issued at 319 PM CDT Sat Apr 27 2024 Short Term...Tonight and Sunday Gusty southwest winds will continue ahead of an approaching cold front slated to track through the region late this afternoon into early this evening. Despite the passage of this cold front, precipitation chances will remain low for east-central Wisconsin as model soundings show a substantial mid-level capping inversion in place around 750 mb with abundant dry air. Although some showers and thunderstorms could develop in the far southeast corner of the cwa in Manitowoc or Calumet counties, hi-res models keep most of the activity to the southeast or only in these counties for a brief period of time. Therefore, will only keep a small chance for convection late this afternoon and early this evening (20-30 percent) before the cold front tracks through the area. Any convection that can develop will have the potential to be severe given the SBCAPE values of 1000-1400 J/kg and bulk shear values of 40 to 45 knots; however, hodographs show that despite decent veering of direction and speed in the lowest 3 km, there is backing between 3 to 6 km, which would act to inhibit updraft development as dry air gets entrained within the storm. Therefore, confidence in seeing severe weather even across the southeastern portion of the cwa is rather low despite the decent parameters. A low pressure system lifting north towards Iowa on Sunday will bring a swath of rain showers and embedded elevated thunderstorms late tonight from the southwest and spread across the rest of the area during the day on Sunday. Cool northeast winds on Sunday will make for a fairly cool day when combined with the persistent rain showers expected. Long Term...Sunday Night Through Saturday Precipitation...Rain showers and a few embedded thunderstorms will be ongoing at the start of this forecast period for Sunday night as a warm front gradually lifts north across the state, paired with an increasing low-level jet. Although there are timing differences in the placement and timing of the warm front (some guidance delays the front lifting north till Monday morning), there is still decent agreement with the forecast area seeing an increase in rainfall between Sunday night and Monday morning. PWATs during this time will be between 1 and 1.40 inches, leaving the potential for localized heavy rainfall, leading to possible flash flooding, especially in urban areas. A few elevated thunderstorms are possible throughout Sunday night into Monday morning, however, the potential for severe storms looks low given the uncertainty in the timing and placement of the warm front. Precip will decrease in intensity for the remainder of Monday, as the warm front's surface low tracks northeast across the state. The precip should come to an end Monday evening/night. Surface ridging will build over the area for Tuesday, resulting in dry conditions. A quick-moving shortwave and surface cold front will bring the next chance for precip Tuesday night, and exit by Wednesday afternoon. A few elevated thunderstorms are possible, but given the timing of the precip, the potential for severe storms is low at this time. Details for the remainder of the forecast period are unclear, but there appears to be some agreement with a prolonged period of precip chances to end the week and continue for a portion of the weekend. Temperatures...With a warm front expected to lift over the region on Monday, normal or above normal highs are anticipated ranging from the mid to upper 50s in north-central WI to the mid to upper 60s in east-central WI. The warm air will stick around for Tuesday, allowing all locations to warm above normal with readings ranging from the mid 60s to low 70s. Due to the timing of the cold front occurring Tuesday night, temperatures should be able to rebound quickly enough on Wednesday to remain above normal. With potential for rainfall for the remainder of the extended, temperatures will take a dip back to closer to normal. && .AVIATION...for 18Z TAF Issuance Issued at 1230 PM CDT Sat Apr 27 2024 Windy conditions will continue at the TAF sites this afternoon with southwest winds gusting to 30 to 40 knots at times. Winds will slowly ease this evening below 20 knots then increase again late tonight into Sunday morning as they turn to the northeast and gust to around 20 knots. Isolated showers and storms may redevelop after 22z, mainly south and southeast of GRB and ATW as a cold front moves through the area. After these showers and storms end this evening, most of the night should stay mainly dry. Ceilings will be IFR near the Lake Michigan shore, although satellite imagery shows the low stratus is dissipating from south to north. MVFR ceilings are expected across north-central Wisconsin with VFR across most of central and east-central Wisconsin. Other than RHI, most sites will be VFR this evening then trend towards MVFR late tonight into Sunday morning. Another low pressure system will bring steady rain to the area late tonight into Sunday morning and last through Sunday night. && .GRB WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 4 PM CDT this afternoon for WIZ030-031- 035>040-045-048>050. && $$ DISCUSSION.....Kurimski/Kruk AVIATION.......Kurimski