Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
030 FXUS63 KMKX 231929 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI Issued by National Weather Service Green Bay WI 229 PM CDT Sun Jun 23 2024 .KEY MESSAGES... - River rises will continue early this week with some of the rivers at minor flood stage. - Showers and thunderstorms will become likely once again late Monday night into Tuesday. Severe thunderstorms will be possible, while any heavy rain could aggravate the ongoing flooding. - Heat index values into the 90s will be possible on Tuesday. && .SHORT TERM... Issued 230 PM CDT Sun Jun 23 2024 Tonight and Monday: A vigorous mid level shortwave, shown on water vapor imagery over western Lake Superior, will dive southeast through Wisconsin late this afternoon and early this evening. As this shortwave tracks through the area, some modest shallow SBCAPE values of 100 to 300 J/kg could produce some scattered showers across eastern Wisconsin. The showers will dissipate later this evening with the loss of daytime heating as the shortwave tracks through the southern Great Lakes. Skies will become mostly clear tonight which, along with the recent rainfall, will lead to some patchy fog across the region late tonight into Monday morning. The fog could be locally dense at time, especially near area lakes and rivers. Lows tonight are expected to mainly be in the upper 50s to lower 60s. A ridge of high pressure will track through the western Great Lakes on Monday, which is expected to keep the area dry. Highs on Monday are expected to range from the middle to upper 70s near the lake, to the lower 80s inland. Kurimski && .LONG TERM... Issued 230 PM CDT Sun Jun 23 2024 Monday night through Saturday: An MCS developing across eastern Minnesota and northwest Wisconsin is forecast to track through northern Wisconsin Monday evening, then southern Wisconsin during the overnight hours into Tuesday morning. While the timing of this MCS through southern Wisconsin is not ideal, after midnight, MUCAPEs across southern Wisconsin are still a respectable 1000-2000 J/kg along with bulk shear values around 40 knots. Model soundings indicate that although these storms will be elevated given a steep low level inversion, CAPE profiles in the hail growth zone are quite girthy with 60 knots of winds lurking at 2k ft above the ground. Therefore, damaging winds and large hail will be a possibility as the MCS rolls through Wisconsin. This scenario is not a guarantee as not all models agree that the MCS will affect southern Wisconsin, with some models not developing one at all given the high CIN values. However, there are enough model members, greater than 50%, that develop and bring it though the area to keep POPs high late Monday night. In addition to the severe weather potential, an MCS tracking through the region could easily bring around an inch of rain. This would exacerbate any flooding that is already ongoing across rivers and streams across southern Wisconsin. A cold front will track through the region Tuesday afternoon, which could set off another round of showers and thunderstorms into Tuesday night. Although the region is outlooked for additional severe weather from this round of activity, with SBCAPE values around 3000 J/kg and 40 knots of bulk shear, models are mainly focused on northern Illinois for the strongest storms as the nose of the 850 mb LLJ is pointed over this region. Before the cold front moves through the region, heat index values will soar to dangerous values on Tuesday. The combination of temperatures near 90 and dew points of 70 to 75 will cause heat index values to soar into the middle 90s. High pressure will then build in across southern Canada, with a ridge of high pressure extending south over the western Great Lakes region during the middle of the week. This will keep the area dry for Wednesday and Thursday as the high tracks through the area. A low pressure system developing across the northern Plains will bring additional chances for showers and thunderstorms to southern Wisconsin late in the week as it tracks through the region. The system is slated to bring a strong cold front through the area Friday night into early Saturday, which could bring heavy rain and strong storms back to the region. High pressure building in behind the departing cold front will then keep the rest of the weekend dry from Saturday afternoon through next Sunday. Kurimski && .AVIATION... Issued 101 PM CDT Sun Jun 23 2024 MVFR conditions will continue early this afternoon, slowly lifting to VFR by mid-afternoon. Lingering sprinkles or light showers will remain possible with these low clouds. Another small chance for a shower or two later this afternoon and evening, especially at SBM. A rumble of thunder can`t be ruled out, but chance to low to include. Look for mainly VFR conditions tonight into Monday morning, but some WI River Valley fog is expected. Some fog could sneak into the TAF sites, but confidence too low to include. Bersch && .MARINE... Issued 230 PM CDT Sun Jun 23 2024 High pressure will shift east across the lake late tonight through Monday morning with much lighter winds expected. Modest south winds will develop for Monday afternoon and night, but become breezy on Tuesday as low pressure around 29.2 inches moves across northern Ontario. Modest westerly winds will then shift to northerly Tuesday night and Wednesday following the passage of a cold front. Another stormy period of weather is expected for late Monday night and Tuesday. Kurimski && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee