Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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627 FXUS63 KGRB 032312 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 612 PM CDT Fri May 3 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Scattered showers and isolated thunderstorms are expected Saturday into Saturday evening, with additional showers and thunderstorms Tuesday through Wednesday. - A few rivers will remain at or reach bankfull stage into the weekend. && .DISCUSSION... Issued at 340 PM CDT Fri May 3 2024 Short Term...Tonight and Saturday Deep mixing allowed temperatures to soar into the middle 60s to lower 70s, caused winds to gust to 25 to 35 mph over far N WI, and resulted in pockets of low relative humidity in the sandy soil regions of northern and central WI this afternoon. Mostly clear skies will give way to a gradual increase in mid and high level clouds overnight, but dry conditions will prevail. Considered the possibility of patchy fog overnight, but a well- mixed air mass, increasing boundary layer winds overnight and shorter spring night argued against any mention at this time. Look for low temperatures to drop into the 40s. On Saturday, a dry start to the day will give way to a band of light to moderate showers along and ahead of a cold frontal passage. The showers will be aided by a weak surface wave lifting northeast along the front, plus upper divergence in the RRQ of a 110 kt jet streak and weak short-wave energy. There is a general consensus for a narrow ribbon of weak instability (SBCAPE 200-400 j/kg) developing over the Fox Valley and lakeshore areas in the afternoon, so have kept a mention of a few thunderstorms there. Showers should arrive in NC/C WI mid to late morning, and Fox Valley/lakeshore early to mid afternoon. High temperatures will range from the upper 50s and lower 60s west and near Lake Michigan, to 65 to 70 across inland areas of NE/EC WI. Long Term...Saturday Night Through Friday Saturday evening/night...Rain and a few thunderstorms will be ongoing across far eastern WI into Saturday evening as a cold front and mid-level shortwave tracks over the area. Not anticipating for these storms to be strong or severe as the couple hundred J/kg of instability over the area during the afternoon will rapidly decrease into the evening. The showers and storms will exit the state by 06z Sunday. Sunday through Monday...High pressure and upper-level ridging moves over the area during this time period, leaving dry weather and mostly sunny skies across the forecast area. Temperatures will rise above normal for both days with highs ranging from the mid 60s to low 70s inland, and upper 50s to low 60s along the lakeshore. Slightly elevated fire weather conditions are possible on Monday as afternoon RH values will be in the 30s and southeast winds may gust to 20 to 25 mph. Locations across the north would be of greatest concern where green up has not fully occurred. Rest of the extended...Models are still in agreement with an upper- level trough developing over the Northern Plains Monday into Tuesday. This will leave the forecast area in the southerly flow ahead of the trough, allowing southern stream energy and moisture to increase and lift into the Middle and Upper Mississippi Valleys. Although there are still some timing and placement differences, especially when the precip will end, Tuesday into Tuesday evening appears to be the best timing for widespread rain and embedded thunderstorms. Despite being in the warm sector, the timing of the precip may hinder severe potential across the forecast area and keep it confined south of the area. Will continue to monitor as there is still plenty of time for the details to be ironed out over the coming days. Details for the remainder of the extended become very messy, but models agree with additional chances for precip at times through the rest of next work week. && .AVIATION...for 00Z TAF Issuance Issued at 612 PM CDT Fri May 3 2024 Expect VFR conditions to prevail through midday Saturday, with patchy mid/high clouds expected into early Saturday. Thickening and lowering clouds are expected in NC/C WI as showers arrive toward midday and C/NE WI Saturday afternoon. Conditions will deteriorate to MVFR Saturday afternoon as the showers arrive. Considered the possibility of patchy fog tonight, but the air mass was well mixed this afternoon (warm temps and low dew points leading to large dew point depressions) and boundary layer winds will be increasing to 20 to 25 kts late tonight. Models are hinting at some low clouds coming off Lake Michigan (near MTW) Saturday morning, but confidence is too low to mention a ceiling at this time. Gusty west winds will drop off quickly this evening, become light SE overnight, then moderate SE-S later Saturday morning and SW Saturday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch/Kruk AVIATION.......Kurimski