Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
419 FXUS63 KMKX 231805 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 105 PM CDT Thu May 23 2024 .KEY MESSAGES... - Two rounds of showers and thunderstorms will likely occur from Friday morning into Friday evening. There is a potential for severe thunderstorms with the 2nd round of storms. && .UPDATE... Issued 104 PM CDT Thu May 23 2024 Broken high based cumulus has formed as a weak shortwave trough moves across central and srn WI this afternoon. There is also very weak low to mid level warm advection occurring around the high. Fcst soundings and CAMs suggest central WI is the preferred area for isold to sct showers and isold storm development this afternoon, with some lgt showers already developing over said area. Increased PoPs to 30-40 percent toward central WI through the afternoon. Otherwise high temps in the middle to upper 70s looks good for today while a lake breeze at the lake front will move inland later this afternoon. Upper ridging and a quiet night is then expected. For Fri, a negative tilt upper wave and associated sfc low will move from the ern Dakotas into Canada while deepening then occluding. A surge of low to mid level warm, moist advection and elevated CAPE will bring a 1st round of showers and storms from west to east across srn WI Fri AM into the early afternoon, with some weakening expected in the east, especially toward east central WI. A few hours or more of decreasing pcpn coverage and the nwd advance of the warm front is then expected over srn WI before the cold front arrives from late afternoon into the evening. There is uncertainty on the airmass recovery and the amount of MLCAPE and MLCIN within the narrow warm sector, but believe MLCAPE of 1000 J/KG is very probable while some MLCIN will remain. However some PVA should aid the frontal forcing and most CAMs and models do suggest another round of storms. Deep layer shear will range from 30-45 kts while 0-2km SRH will likely be rather high around 200-300 m2/s2 as veering profiles remain in the narrow warm sector. As the fronts advance the lake breeze should eventually retreat toward the lake but early afternoon convection could reinforce it as well. All SVR threats will be possible with supercellular development and/or QLCS development. If the airmass recovery suffers, any meaningful MLCIN would keep the tornado threat rather small. Nwly winds and cold advection will then drop temps into the middle 40s to lower 50s by sunrise Sat. High pressure will then shift across the state on Sat with temps rebounding into the lower 70s for the afternoon. Gehring && .SHORT TERM... Issued 419 AM CDT Thu May 23 2024 Today through Friday: Friday is a complex weather day. A line of storms is expected to develop over eastern SD/NE tonight, which would be associated with a midlevel shortwave trough and a coincident warm front on the nose of a nocturnal low level jet. The parent mid level closed low will be over the western Dakotas during this time, so the system will be occluding. The line of storms should be just east of Des Moines at 12Z/7 AM Friday morning, with the northward extent near the Twin Cities and the southward extent possibly down to Kansas City, per the meso models. The line may hold together as it tracks across southern WI Friday morning, but it should be weakening as it gets farther away from that parent upper low. Models have that exiting or dissipating midday, so we can call that the morning round. This morning round has the potential to bring gusty winds west of Madison if it manages to remain organized. If it falls apart due to the lack of upper forcing and the weakening low level jet, then there may be a stalled boundary lingering over south central WI. The next mid level shortwave will arrive in south central WI mid afternoon, along with a surface cold front. Around the same time, a weak shortwave will be rolling across MO and southern IL. With high instability there, a storm complex with broken lines of storms is anticipated to develop and have upscale growth where it zippers northward just ahead of the cold front and phases with that WI shortwave. As long as that morning round didn`t work over the environment in southern WI too much, we should have thunderstorms develop along this shortwave, area of surface convergence, and nose of the low level jet. Dewpoints should creep into the lower 60s near the WI/IL border ahead of this front, so CAPE is forecast to be 1000 to 1500 j/kg in southern WI. The 0-3km shear is very high (35-40 kt) due to southeast winds at the surface and SSW winds with the low level jet. These ingredients are favorable for qlcs tornado development with any line of storms moving ENE. However, the main severe threat with these anticipated storms with the afternoon round is wind damage. Timing of these storms across southern WI looks like roughly 3 to 8 PM, but the forecast timing between the models is all over the place. Temperatures Friday are uncertain due to the uncertainty of the thunderstorm coverage, but highs should be in the mid to upper 70s. Cronce && .LONG TERM... Issued 419 AM CDT Thu May 23 2024 Friday Night through Wednesday: The actual cold front will probably lag behind the convective line Friday night and feature a wind shift to the northwest. Cooler temperatures are expected on Saturday of Memorial Day weekend with highs in the lower 70s. Sunshine will prevail with high pressure and light winds overhead. The next system of interest will arrive Sunday morning with a mid level shortwave trough and surface low tracking through MO, IL and WI. Right now it looks like the mid level lapse rates will be weak, so not a lot of instability to work with to develop stronger storms. The next shortwave trough looks more robust and is expected to swing across IL Monday night or Tuesday morning. These shortwaves are rotating around a closed low that will be sitting over the Upper Great Lakes or Quebec, depending on which model you choose. Nevertheless, we can expect rounds of showers with a few thunderstorms Sunday through Tuesday. We will transition to a zonal pattern by the end of the week which should give us a break in the storm complexes. Cronce && .AVIATION... Issued 104 PM CDT Thu May 23 2024 Sct-bkn050-070 cumulus this afternoon with scattered showers and isold storm development toward central WI. The precipitation will end by early evening with a quiet night and VFR conditions expected. Showers and storms will then move west to east across srn WI during the morning daylight hours of Fri. There will be a break of a few hours or so followed by more showers and storms late afternoon and early evening. Areas of MVFR Cigs will be possible over south central WI throughout the day and may spread into ern WI for the evening. Gehring && .MARINE... Issued 419 AM CDT Thu May 23 2024 High pressure will drift across the Great Lakes today. Light to modest westerly winds will prevail over the entire lake. Winds will become east-southeast on Friday as a low pressure trough approaches from Wisconsin. Thunderstorms are likely along this trough Friday afternoon and night. Winds will shift to the west in the wake of the trough Saturday morning and high pressure will overspread the Lake Michigan. Low pressure will slide across the Midwest Sunday and across Lower Michigan Monday. Cronce && .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