Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
487 FXUS63 KMKX 241948 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 248 PM CDT Mon Jun 24 2024 .KEY MESSAGES... - A strong to severe line of fast moving thunderstorms is expected to move across southern WI late this evening and overnight. Damaging winds will be the main threat. - Urban and small stream flooding will be possible after midnight due to the already saturated conditions and a quick burst of torrential rainfall. - River rises will continue early this week and may receive a sudden boost from heavy rain after midnight. - Heat index values into the 90s will be possible on Tuesday. && .SHORT TERM... Issued 248 PM CDT Mon Jun 24 2024 Tonight through Tuesday night: Main concern heading into tonight will be MCS activity and an associated severe wind threat. Convection is still on track to develop in the vicinity of the Minnesota/Wisconsin state line this evening, congealing into an MCS as it pushes southeastward into the area. With a strongly unstable airmass aloft feeding this complex, it will be capable of producing high winds, especially near the apex of any bowing segments. Outside of that, look for sporadic wet microbursts within the areas of heaviest rain. Limited low level CAPE and shear will greatly limit the QLCS tornado threat. The biggest question right now remains the exact track of the MCS, which will be highly dependent on where exactly convection forms late this afternoon/early this evening, and how quickly cold pools are able to conglomerate. Once cold pool conglomeration takes place, the complex should pretty closely follow the northwest to southeast instability gradient and the forward propagating Corfidi vectors. The latest forecasts suggest that this complex could arrive in our north as early as 10 PM, but more likely close to midnight. It should clear the area by 4 or 5 AM. This should be a fast enough motion to limit any widespread flooding issues, but with high rainfall rates and already saturated ground, there could be some localized issues. Heading into Tuesday, it seems increasingly likely that the outflow from tonight`s activity will be far enough south to keep the vast majority of the convection south of the state line through the day. We will still get quite warm and humid, especially south of I-94, with highs in the upper 80s to around 90, and heat indices between 90 and 95. A cold front brings a cooler and drier airmass into the region Tuesday night into Wednesday. Boxell && .LONG TERM... Issued 248 PM CDT Mon Jun 24 2024 Wednesday through Monday: Mid-level and surface troughing still look to move across Wisconsin on Wednesday in the wake of the low pressure moving across the state Monday and Tuesday. GFS and NAM soundings show dry mid to upper levels but a well mixed boundary layer, so expecting just cumulus to develop across southern Wisconsin Wednesday afternoon and have kept the forecast dry with highs near 80F. However, given dynamic forcing via the troughing, moisture in the lower levels, and the well mixed boundary layer I wouldn`t be surprised to see a stray shower or two. High pressure then sinks south into Wisconsin Wednesday night which will bring clear skies and potentially allow fog to develop given radiational cooling and the abundant amount of moisture across the southern part of the state. Upper level ridging and high pressure will remain in place across Wisconsin on Thursday allowing for quiet weather and temperatures in the 70s before moving east Thursday night. Southerly flow will return Thursday night into Friday morning, bringing strong warm and moist advection into the state. Soundings indicate a very saturated column Friday morning with PWATs around 2in which combined with a weak shortwave trough at 500hPa could provide for heavy rainfall. A strong cold front will then move across the state Friday evening. There is some uncertainty with the timing of the front as the GFS/Euro/Canadian differ slightly with when it comes through, but steepening mid-level lapse rates and modest MUCAPE may allow for some elevated, but strong to severe storms Friday night into Saturday. High pressure will then again sink south Saturday behind a weak surface trough. This will allow for drier and cooler weather across southern Wisconsin for the beginning of next week. Falkinham && .AVIATION... Issued 248 PM CDT Mon Jun 24 2024 South winds are expected into this evening, with low level wind shear developing as a low level just noses into the area. A complex of thunderstorms is then expected to affect most, and perhaps all, of the terminals overnight, bringing reduced visibilities, lower ceilings and strong gusty winds. The complex should clear the terminals by daybreak with westerly winds through much of the day on Tuesday. Boxell && .MARINE... Issued 248 PM CDT Mon Jun 24 2024 Modest south winds will develop this evening, becoming breezy late tonight into Tuesday morning as low pressure inches moves across northern Ontario. A Small Craft Advisory is in effect overnight for the nearshore waters. A line of thunderstorms with very gusty winds will move across Lake Michigan late tonight through early Tuesday morning. West winds on Tuesday will then shift to northerly on Wednesday following the passage of a cold front. High pressure will move across the lake Wednesday night through Friday morning, bringing pleasant weather. Boxell && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...1 AM Tuesday to 7 AM Tuesday. && $$ 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