####018005371#### FXUS63 KGRB 040329 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1029 PM CDT Fri May 3 2024 Updated aviation portion for 06Z 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 06Z TAF Issuance Issued at 1028 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. Some thunderstorms are possible, but chances are low enough to leave out of the TAFs. Conditions will deteriorate to MVFR Saturday afternoon as the showers arrive, then improve back to VFR Saturday evening as the showers end and skies scatter out. Considered the possibility of patchy fog overnight, 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. Light SE surface winds are expected overnight, then moderate SE-S later Saturday morning and SW Saturday afternoon turning NW Saturday evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch/Kruk AVIATION.......Kurimski ####018005279#### FXUS63 KFSD 040331 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1031 PM CDT Fri May 3 2024 .KEY MESSAGES... - Rain is expected to move through after dark and into Saturday morning. Rainfall amounts from 0.25" to 1" may be possible. Highest amounts in Northwest Iowa could lead to minor increases in already ongoing flooding. - Cooler temperatures on Saturday (low 60s), with middle and upper 60s on Sunday. Dry conditions expected both days. - Winds approaching advisory criteria may arrive Monday, prior to the arrival of late afternoon and overnight thunderstorms. - The greatest severe weather risks continue to remain focused south of the Missouri River and Highway 20 corridor, however continue monitoring of the forecast is recommended. && .DISCUSSION... Issued at 623 PM CDT Fri May 3 2024 Surface obs indicate the location of the cold front to be in a line roughly from Mission South Dakota northeast through Redfield South Dakota. This front will continue to advance southeastward through the afternoon and evening. Strong frontogenesis in concert with the front will trigger showers and maybe even some thunder. Current radar indicates light rain showers over central South Dakota. These showers will advance along with the front. There is little in the way of instability tonight, so we do not expect these showers to become severe. However, some of the rain showers could produce significant rainfall, especially over northwestern Iowa, where a half to an inch is possible. Elsewhere, totals are expected to be around a quarter to a half inch. Rain showers will be well east of our area by mid Saturday morning. Lows for tonight will be cool, in the upper 30s to 40s. Clouds thin as high pressure builds in Saturday, revealing sunny skies for the afternoon. Winds will be northwesterly bringing a healthy dose of CAA southward, limiting our highs to the upper 50s and 60s. The overnight lows will again be cool, in the upper 30s and 40s. As the high moves to the east, winds will swing around to the southeast Sunday. WAA in the 850 mb level warms temperatures there into the 6-10 deg C range. This indicates that highs at the surface will warm into the mid 60s to low 70s. Sunday night, a low pressure system begins to push through the Rockies, tightening the SPG in front of it. Winds will increase overnight and through the day Monday. I felt that the NBM winds were too strong after considering the model soundings. After collaboration with neighboring offices, went with a 50/50 blend of the NBM and CONSALL. Even after knocking winds back a bit, we are still looking at strong winds for Monday. Sustained at 30-35 mph with gusts 40-45 mph. It may be necessary as we get more information to include a headline for winds, but at this time confidence is too low. Monday morning the surface low ejects out of the Rockies into the north-central Plains, bringing the next round of showers and thunderstorms. Models this round have come into better agreement on the low exiting Colorado and taking a sharp northeasterly track through western Nebraska and South Dakota. As it does so, it will drag a warm front across eastern Nebraska and South Dakota. Instability in the warm sector increases to 500-1000 J/kg of CAPE. Enough to support some thunderstorms. The more favorable environment for severe weather remains over the central Plains, however, a few strong to severe thunderstorms are still possible over southeastern South Dakota and northwestern Iowa Monday night into early Tuesday. Rain totals are still a question mark, with ensembles indicate 80- 100% probability of exceeding 0.1 inches, and 30-60% probability of exceeding 0.5 inches. Rain is expected to be east of the area by Tuesday afternoon. Highs will be 70s for Monday and 60s for Tuesday. The low pressure system then hangs out over the northern plains for the rest of the week, gradually occluding and then moving off to the southeast. Multiple shortwaves form and pass through the area off of that main system, bringing multiple chances for showers through the week. Temperatures will be in the 60s. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1029 PM CDT Fri May 3 2024 Frontal band of rain continues to make slow progress eastward late this evening. Meanwhile, convection over central Nebraska will continue to move east and northeast into the overnight hours. These two areas will merge after 1am over the Tri-State area, with potential for MVFR ceilings and visibility through the pre-dawn hours. In Sioux City,will not rule out some stronger 35 knot winds at times as convection passes through the area. Rain moves east of the CWA by 12Z, with MVFR ceilings hanging on through the morning. Eventually ceilings will scattered with some limited low-lvl instability shower/sprinkle potential in the afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...AJP AVIATION...Dux