Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
992 FXUS63 KMKX 212135 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 435 PM CDT Fri Jun 21 2024 .KEY MESSAGES... - Flood Watch continues for flash flooding potential for portions of south central and southeast WI continues through Saturday evening. Multiple rounds of showers and storms are expected with rainfall amounts between 1-3 inches and locally higher amounts exceeding 2 inches, especially for areas west of I39/90 corridor. - Could see a stronger thunderstorm or two later this afternoon and evening with gusty winds. However, there will be a better potential for stronger to severe thunderstorms Saturday afternoon/evening (risk 2 out of 5). With any thunderstorms damaging winds will be the main hazard, but large hail and an isolated tornado is not out of the question. - Heat indices will climb back into the upper 80s to mid 90s Friday and again Saturday, especially for inland areas along and south of I- 94/HWY-18. && .SHORT TERM... Issued 427 PM CDT Fri Jun 21 2024 Tonight through Saturday night: The outflow boundary from upstream convection this morning continues to be focus for shower and thunderstorm development this afternoon, especially as it interacts with the effective warm front which is strung across east central WI. While most storms have been brief as they are struggling to maintain their longevity given meager shear (<30 knot), any interactions with nearby storms and any boundaries can help maintain these storms a bit longer especially as the airmass destabilized and SBCAPE has climbed to around 1000-2000 J/kg. Any of this type of activity can result in localized gusty winds, but more likely resulting in heavy rainfall given the slow movement. Localized flash and/or river flooding will be possible with any storms lingering or moving over the same area for extended period of times through the evening. Overall, the higher shower and thunderstorm potential through this evening will be for areas along and north of Highway-151, while areas south-southeast will be more scattered activity this evening. However, areas closer to Lake Michigan are behind a lake breeze and with the more stale marine environment will have a lesser threat for thunderstorms. Will continue to see shower and storms overnight linger along the boundary, but thinking the scattered cover will decrease overnight. Some CAMs have a round of showers and storm moves through early in the morning and clearing out just mid morning. With the warm front lingering across the northern tier of the CWA and morning activity moving out, the late morning/afternoon should have enough time to recover and destabilized before Saturday afternoon activity develops and swings across the area. Saturday afternoon and evening holds the better potential for more scattered strong to severe thunderstorm potential. Upper-level dynamics align over the region favoring thunderstorm development given a strengthening +40 knot LLJ and shortwave trough aligning with the cold frontal passage. PWATs look to be around 1.5-2.0 inches and given hi-res CAMs and HREF ping SBCAPE 1500-2000 J/kg the environment will be conducive for thunderstorm development. However, with deterministic progging deep layer (0-6km) between 30-40 knots, it will be enough to maintain thunderstorms upscale growth. Most CAMs agree on this activity Saturday afternoon/evening growing into more of a linear feature ahead of the cold front. However, cannot rule out an isolated storm our two to develop ahead of the main line across the warm sector, especially with any lingering outflow/mesoscale boundaries from convection earlier in the day. Additional HRRR model sounding hodographs do show some decent low- level (0-3km) SRH 100-150 m2/s2, so low-end isolated tornadoes threat cannot be ruled out if anything develops. Otherwise, while cannot rule out a embedded tornado within the linear mode especially with any bowing/surges, the chances are low given shear vectors are more parallel to the line. Thus the main concern will be damaging winds as the line pushes through. One caveat to the severe potential for Saturday will be where the warm front boundary ends up by by the afternoon. The 12z models favored it more across central WI, while the 18z has trended it a bit further south. Thus if the southern trend continues it may pull the severe threat south with it. Nevertheless, the potential remains for a line of severe thunderstorms to work their way across southern WI Saturday afternoon and evening bring damaging winds and heavy rainfall/flooding threat along with a non-zero isolated tornado threat. Otherwise, areas south of the warm front will see temps warm back into mid to upper 80s with heat indices in the low to mid 90s. However, expect it to be cooler north of wherever the front sets up and for areas along the lakeshore. Wagner && .LONG TERM... Issued 427 PM CDT Fri Jun 21 2024 Sunday through Friday: Sunday should be a pleasant day with highs near 80 and lower humidity. Short waves will impact the area late Sun/Sun night and Tue/Tue night. A weak cold front will pass through the area late Sun/Sun night. FROPA is expected to be dry at this time. If there were to be precip with this FROPA, E cntrl WI would be favored. The next short wave is due in for Tue PM/Tue night which will be responsible for the next chance of rain (30%-50%) late Mon night through Tue night. NW upper level flow will keep things dry through the end of the period as a 1020 mb SFC ridge moves across WI Thu. BM && .AVIATION... Issued 427 PM CDT Fri Jun 21 2024 Additional development ongoing across southern WI as outflow boundaries make there way across the area. Shower and storm this afternoon afternoon will bring heavy rainfall reducing flight conditions. Also cannot rule out a stronger storm or two this afternoon and evening with gusty winds being the main concern. Additional shower and thunderstorm activity expected overnight in Saturday. Wagner && .MARINE... Issued 427 PM CDT Fri Jun 21 2024 Expect light northerly winds over Lake Michigan today as high pressure weakens over Lake Superior. Light northeast winds this evening will then shift to modest southerly over the southern half of the lake as a warm front moves northward. The warm front and southerly winds will then extend into the northern portion of the lake for Saturday followed by low pressure tracking east across central Lake Michigan early Saturday evening. A cold front will quickly follow with modest northwest winds over the entire lake for Sunday. Rounds of thunderstorms are expected across the lake at times from this afternoon into Saturday night. Wagner && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058- WIZ059-WIZ062-WIZ063-WIZ064-WIZ065-WIZ067-WIZ068-WIZ069 until 7 PM Saturday. 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