Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
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995 FXUS63 KMKX 230921 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 421 AM CDT Thu May 23 2024 .KEY MESSAGES... - Two rounds of showers and thunderstorms will likely occur Friday morning and late Friday afternoon. Gusty winds are the main threat. && .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 419 AM CDT Thu May 23 2024 A weak shortwave tracking from IA to southern WI this morning through early afternoon is expected to provide steep mid level lapse rates again today. The better chance of pop-up thunderstorms is west of Madison again. Bases will be VFR around 7000 ft outside of any convection. Cronce && .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