Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
449 FXUS63 KMKX 180135 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 835 PM CDT Mon Jun 17 2024 .KEY MESSAGES... - Scattered storms with gusty winds toward central WI tonight. - Hot and humid conditions through Wednesday, with temperatures and heat index values in the 90s. - There will be daily thunderstorm chances through the week due to warm and humid conditions, with the highest rain chances Wednesday afternoon (as a weak cold front approaches). - Dangerous swim conditions are possible Tuesday afternoon at Lake Michigan beaches in Sheboygan and Ozaukee Counties. && .UPDATE... Issued 835 PM CDT Mon Jun 17 2024 The MCS over west central WI has been encountering a higher CAPE and DCAPE environment with movement more to the right of the mean wind than earlier. With the exception of the strong cell in ne Monroe County, the gust front has been well out ahead of the line with no known reports of high winds at this time. Will count on the srn end of the line to affect MQT and Green Lake Counties late this evening. Gusty winds will certainly be possible even with cells developing well behind the gust front given MLCAPE values of 2000-2500 J/KG and DCAPE around 1000 J/KG. Gehring && .SHORT TERM... Issued 310 PM CDT Mon Jun 17 2024 Tonight through Tuesday night: Scattered thunderstorms capable of small hail and gusty winds are currently developing along a Lone Rock to WI Dells line, co- located with outflow boundaries left behind by morning convection. Additional auto-convective development has occurred (in a more isolated manner) further east, including at least two brief thunderstorms triggered by lakeshore convergence (though no lake breeze has moved inland). These storms will likely persist until a few hours after daytime heating shuts down. A select few CAMs allow continued southerly WAA to create a few weak showers late tonight into Tuesday morning. The highest PoPs for this (12%) are southeast towards Kenosha, where a passing 500mb shortwave provides enough PVA Tuesday AM to justify a shower / weak thunderstorm chance. The 250mb ridge lingers into Tuesday, with similarly warm and humid conditions likely (though currently looking a degree or two cooler than today). Due south winds over the lake and land may allow a weak lake breeze circulation (apparent as a slight southeastward tilt to the wind in lakeshore counties) to ventilate the lakefront (especially far eastern Sheboygan county and Wind Point in Racine) to hold temperatures to the low to mid 80s. Still expecting a daytime high in the low 90s for Milwaukee unless the lake breeze over-performs. With the warm and humid airmass, daytime heating may lead to the development of afternoon thunderstorms (15% chance), once again with a threat for gusty winds and small hail, though there is a distinct lack of triggering mechanisms (besides daytime heating, a weak thermally-direct circulation from the lake breeze, and the potential for weak AM convection to drop outflow boundaries). Only 10 to 25 kts of deep shear expected, so no well- organized thunderstorms are expected. Tuesday afternoon has a very similar parameter space (roughly 1.5 inch PWAT, SBCAPE > 2000 joules, DCAPE just over 1000 joules, EBWD of 15 kts, and a subsidence inversion weakening mid-level lapse rates). This would favor widely scattered ordinary cells, with a threat for gusty winds, but only small hail possible. Sheppard && .LONG TERM... Issued 310 PM CDT Mon Jun 17 2024 Wednesday through Monday: Heading into Wednesday, precipitation chances in Wisconsin increase as the southern edge of the northern low rides the crest of the thermal ridge. A very weak cold front makes its way through the area Wednesday evening bringing scattered showers/storms throughout Wednesday (60% rain chances) and continuing into Thursday. Some uncertainty remains for exact areas affected by precipitation throughout the weekend but the best chances for shower/storm development remains across all of southern Wisconsin. This precipitation will continue to linger throughout the weekend due to the development of a strong surface low to our northwest on Saturday. Temperatures will remain cooler once the trailing frontal feature comes through the area. Cooler temperatures will persist throughout the majority of Thursday but quickly warm back up heading into the weekend. Despite the high temperatures, general cloudiness is expected Wednesday onward. However, the continuous spread of humid conditions will carry on until Monday. MT && .AVIATION... Issued 835 PM CDT Mon Jun 17 2024 Few-sct050-060 cumulus with high cirrus at times tnt, but scattered storms toward central WI from late this evening into the overnight. Areas of MVFR Cigs may develop for a few hours from 14-17Z Tue over south central WI due to initial heating and cloud development. Afterward, sct040-050 cumulus expected for the afternoon into the early evening. Gehring && .MARINE... Issued 310 PM CDT Mon Jun 17 2024 Modest southerly winds will prevail through tonight. Low pressure around 29.5 inches lifting from the northern Plains into northwestern Ontario on Tuesday will then produce gusty southerly winds Tuesday through Tuesday night. Light southwesterly winds are then expected as the low continues to lift into the Hudson Bay, with a cold front slowly pushing southward across the lake Wednesday night into Thursday, shifting winds northeasterly. Periods of thunderstorms are expected to continue this afternoon through this evening, with slight chances on Tuesday morning. Slight chances are expected again Tuesday afternoon (mainly across the southern half). Thunderstorms become more likely on Wednesday into Wednesday night across the open waters as the cold front enters the region. Sheppard && .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