Expires:No;;408995 FXUS63 KMKX 261500 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1000 AM CDT Fri Apr 26 2024 .KEY MESSAGES... - Multiple rounds of showers and thunderstorms are expected later today through the weekend, with storms possibly lingering into early Monday. Locally heavy rainfall will be possible. - A few thunderstorms may be severe during this active pattern, particularly later Saturday through Sunday. - Additional chances for showers and storms mid to late week next week. && .UPDATE... Issued 1000 AM CDT Fri Apr 26 2024 Current rain showers are over western Illinois, with some weaker reflectivity values being picked up in far southwestern Wisconsin. Notable dry layer at the lower levels may delay precipitation onset, but otherwise, timing remains on track for the general rain band to enter the area sometime around the afternoon-evening commute. Gertonson && .SHORT TERM... Issued 1000 AM CDT Fri Apr 26 2024 Tonight and Saturday: Persistent moisture and warm air advection will bring rounds of showers to Wisconsin this afternoon into tonight. The first round this afternoon into early evening should be thunder free, but round 2 later evening into tonight should have at least a few rumbles of thunder. Bumped up precip chances, as latest HREF probabilities of 6 hr measurable precip are 80-100 percent as the stronger forcing moves through. Temps will be coolest east today under persistent onshore winds, with highs also a bit cooler in the southwest as the thicker clouds and rain move in this afternoon. Central portions of the forecast area should see temps near normal, topping out at around 60. Temps will stay on the mild side tonight due to the persistent warm air advection, elevated winds, and cloudy conditions. Showers/storms should wind down by sunrise Saturday, with mainly dry weather then expected through the daytime hours as the deeper moisture and stronger forcing move on to the east/northeast. By late afternoon, a few showers and storms could develop mainly northwest of Madison, as a weak low level frontal boundary sags into the area from the northwest. Though clouds may linger through Saturday morning, models suggest enough mixing for some breaks in the clouds by mid- afternoon. Given the warm southwest low level flow, went on the warmer side of models for high temps at 75 to 80 degrees. If the clouds hang on longer into the afternoon though, these forecast highs may be several degrees too mild. DDV && .LONG TERM... Issued 350 AM CDT Fri Apr 26 2024 Saturday night through Thursday: As the first low pressure ejects northeastward from the Great Lakes region Saturday evening, a second (deeper) low pressure drifts northeastward from the central plains. The cool sector from the first low (over northwestern WI) collides with the warm sector of the second low, producing a SW to NE oriented frontal boundary drifting into our CWA Saturday evening / night. The exact timing of this front remains uncertain, but an increase in shower / thunderstorm coverage is expected Saturday evening into Saturday night as the front draws closer. The ECMWF and the GFS both show MUCAPE of roughly 1000 to 2000 Saturday evening south of the front, decreasing to 500 to 900 j/kg south of the front by 1 AM Sunday as we lose daytime heating, suggesting that convection may transfer from surface based to elevated, increasing in coverage and weakening in intensity overnight. Severe hail and thunderstorm wind gusts will be possible Saturday evening, with the hail threat potentially lingering with the elevated convection overnight. A surge in the southwesterly low-level jet arrives Sunday morning, rapidly boosting 850-700mb RH. A corresponding northward push of the surface warm front (ahead of the approaching low) is expected, though the exact timing / positioning of this front (and the surface based instability behind it) remains uncertain. Early Sunday, accelerating northeasterlies off of Lake Michigan are progged to halt the warm front's advance in our northeast CWA, while the front makes more progress in the west. The front then fully overruns the CWA later that evening / overnight. Rain / thunderstorms with localized heavy rainfall and potentially some severe storms remain possible throughout this period. Showers and thunderstorms then linger into Monday as as the cold front from the second low pressure finally pushes through. Next week's weather pattern then features two additional chances for rain as smaller amplitude troughs pass by. Sheppard && .AVIATION... Issued 1000 AM CDT Fri Apr 26 2024 High level clouds remain draped over much of the area, with lowered ceilings pushing in from the southwest. Rain and low level wind shear threat continue to exist going into this afternoon and evening with robust warm air advection over the area by this time. Gertonson && .MARINE... Issued 350 AM CDT Fri Apr 26 2024 Breezy southeast winds are expected today into tonight as low pressure lifts from the Central Plains into Minnesota. Winds will remain elevated Saturday from the south as the low continues to lift northward west of the area. Winds will then flip to northerly from the north Saturday night through at least central portions of the lake, with a frontal boundary likely remaining draped across the southern lake on Sunday. Winds will be southerly south of the front and east to northeast north of the front. A Small Craft Advisory is in effect for today through Monday, through winds and waves may drop below criteria for a time on Sunday. Multiple rounds of showers and storms are expected this evening through the weekend. DDV && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM Monday. && $$ 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