Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
542 FXUS63 KMKX 201507 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1007 AM CDT Thu Jun 20 2024 .KEY MESSAGES... - Scattered thunderstorms possible this afternoon. - Thunderstorms continue on and off into the weekend. A few thunderstorms Friday afternoon could be strong, with better chances for strong to severe storms Saturday afternoon and evening. - A break from the heat on Thursday, but heat index values will be back in the middle 90s Friday and Saturday. && .UPDATE... Issued 1000 AM CDT Thu Jun 20 2024 Morning showers and along the boundary continues to diminish in coverage, but can still see some scattered activity through the remainder of the morning. Will see a lull in shower activity early this afternoon, but additional scattered shower chances pick up this afternoon as the boundary stalls/meanders along the WI/IL border. Afternoon activity looks to be more spotty given the cooler conditions and lack of upper-level support and low- level thermodynamics, but still could see a quick storm or two briefly pop up. Otherwise, the previous forecast remains on track with high pressure influence conditions overnight. Wagner && .SHORT TERM... Issued 507 AM CDT Thu Jun 20 2024 Today through Friday night: A band of showers with a few embedded thunderstorms will continue to progress southeastward through southern Wisconsin this morning exiting and breaking up by midday. Meanwhile, early this morning, patchy fog remains possible in lakeshore counties. Overcast skies and northeasterly winds will serve to keep temperatures lower today, with highs ranging from the low 70s in central and far southeastern Wisconsin to near 80 degrees across far south-central Wisconsin. Lake Michigan lakeshore towns may see temperatures to struggle to get out of the 60s. Scattered thunderstorms may develop during the afternoon hours. Minimal CAPE away from southwestern portions of the area (where up to 1000 J/kg are available) should keep storms from becoming strong. Tonight, additional patchy fog is possible along Lake Michigan as light winds continue and showers end across southeastern Wisconsin. Stalled boundary produces 20-30 percent chance of additional showers and isolated thunderstorms during the overnight hours. Lows in the low to mid 60s are expected. Friday, a developing warm frontal feature will fire off additional thunderstorms, especially during the afternoon (50-70 percent chance). CAPE values increase back into the 1000-2000 J/kg range as temperatures warm into the 80s away from Lake Michigan. A few areas in far southern Wisconsin could see heat index values back in the mid-90s. Bulk effective shear remains marginal around 30 kt, but PWAT values above 1.5 inches and low level frontogenesis may be enough to overcome marginal shear and produce a few downbursts within stronger storms. Showers and storms continue through the overnight hours, although chances diminish back to the 30-50 percent range. MH && .LONG TERM... Issued 507 AM CDT Thu Jun 20 2024 Saturday through Wednesday: Ejecting low pressure in the central Great Plains brings southwesterly winds and puts southern Wisconsin firmly within the warm sector on Saturday. Bulk shear of 35-40 kt and turning within the boundary layer with CAPE around 2000 J/kg could lead to strong storms along a cold front Saturday afternoon and evening. Modeling has been remarkably consistent for the previous several runs with low pressure strengthening and progressing eastward Saturday. That being said, the trough remains positively tilted with northeasterly shear vectors, which may inhibit strength of the eventual line. PWATs remain in over 1.5 inches, which could result in significantly heavy rain within areas seeing multiple rounds of storms. Heat index values may reach the mid-90s once again on Saturday. After a cold frontal passage overnight Saturday, dry conditions under high pressure are expected to start Sunday and linger through early week. Temperatures will slowly increase to near 90 degrees once again by Tuesday. An additional developing system may bring precipitation chances Tuesday into Wednesday (20-30 percent chance). Timing is less certain on this impulse, so kept NBM output for the time being. MH && .AVIATION... Issued 1000 AM CDT Thu Jun 20 2024 Ceilings continue to bounce around this morning with MVFR/IFR conditions as scattered shower activity impacts southern WI terminals. Expect to see these conditions continue through the remainder of the morning before improving this afternoon. There will be additional spotty/scattered shower and a thunderstorm or two possible develop this afternoon as a stalled frontal lingers along the WI/IL. JVL and MSN continue to see the better chances of seeing impacts from this afternoon activity, but cannot rule out a chance for ENW. Otherwise, lighter northeast to easterly winds off Lake Michigan will keep conditions less favorable for shower/storm develop this afternoon. Overnight expect high pressure over Lake Superior to influence the pattern with light winds, but cannot rule out some patchy fog and low ceilings to develop given the increased surface moisture, especially for areas closer to the shores of Lake Michigan. Wagner && .MARINE... Issued 507 AM CDT Thu Jun 20 2024 Patchy dense fog is possible across the southern half early this morning, with more widespread dense fog in nearshore waters from Sheboygan to North Point Lighthouse. Patchy dense fog is possible once again overnight tonight into early Friday morning. Light northeast winds will continue across the lake tonight into Thursday night as high pressure sits over Lake Superior. Low pressure developing in the central High Plains Friday will then allow a stationary front to develop across the open waters, producing periods of thunderstorms. Low pressure will lift into southern Minnesota on Saturday, leading to gusty southerly winds and continued periods of thunderstorms across the lake. Winds shift southwesterly into Saturday night, and westerly on Sunday as low pressure departs to the east. MH && .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