Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
539 FXUS63 KMKX 132029 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 329 PM CDT Tue Aug 13 2024 .KEY MESSAGES... - Isolated to widely scattered showers & thundershowers are possible over east-central and southeastern Wisconsin through the rest of the afternoon. No hazards are expected in this activity. - Two rounds of showers and thunderstorms are expected across the region from late Wednesday night through Thursday. Heavy downpours will be possible in all storms. A few strong to severe storms are possible Thursday afternoon & evening. - Small Craft Advisory conditions are possible in nearshore zones Thursday morning through night. - A high swim risk is possible at local beaches Thursday. - Scattered shower and thunder chances continue Friday through this weekend. && .SHORT TERM... Issued 330 PM CDT Tue Aug 13 2024 Tonight through Wednesday night: Synopsis/Mesoanalysis: High pressure is entrenched across the region early this afternoon, resulting in largely pleasant conditions over southern Wisconsin. Widespread fair weather cumulus development has been noted in recent satellite imagery, with a few rain showers developing over the last 1-2 hours over the greater Milwaukee metro. The aforementioned shower formation is likely linked to enhanced lift along the lake breeze, as well as any additional contributions from upsloping flow along the Kettle Moraine. These near-term trends set the stage for the remainder of the afternoon, with additional widely scattered shower/thundershower development possible along the lake breeze through early evening. Consolidating from several shortwaves originating from the Mountain West, an upper trough will organize over the Northern Plains from late Wednesday, reaching the Upper Mississippi Valley by Thursday morning/the conclusion of the short term period. A combination of increasing DPVA & warm advection ahead of the feature will help to trigger showers and thunderstorms across the region late Wednesday night through predawn Thursday. While severe weather is unlikely, heavy downpours will be possible in this thunderstorm activity. Rest Of This Afternoon: Expect additional isolated to widely scattered showers/thundershowers along the lake breeze as it advances inland. Ongoing development over southeastern Wisconsin has struggled to achieve any appreciable depth, which helps to explain the lack of lightning in this activity. Forecast soundings, as well as observed composite profiles from Mitchell Intl, do depict some instability at/above the -10C level, so an isolated clap of thunder can`t be entirely ruled out in the tallest of this PM`s showers. Apart from the highly isolated lightning potential, no hazards are anticipated in this afternoon`s showers. Tonight: Areas of patchy fog are possible after midnight, particularly in the Wisconsin River Valley & low-lying areas susceptible to cool air drainage. Dense fog is not expected at this time. Wednesday Night: Most locations will remain precip-free through midnight, with shower and thunderstorm chances increasing considerably through the second half of the overnight. As evidenced in forecast soundings, instability will be quite weak across southern Wisconsin as storms move in, translating to negligible severe weather potential in any of this activity. Of greater concern will be widespread 1.5-2.0" precipitable water values pooling ahead of the approaching upper trough. Said readings, which fall anywhere between 1.5 to 2 standard deviations above local climatology for mid- August, will support efficient rainfall rates/heavy downpour potential in tomorrow night`s activity. While widespread flooding concerns are low, brief rises on streams & pooling of water on roadways will be possible in any locations experiencing heavy downpours tomorrow night. Quigley && .LONG TERM... Issued 330 PM CDT Tue Aug 13 2024 Thursday through Tuesday: Synopsis: The upper trough forming over the northern Plains during the short term, will begin to drift across the state on Thursday. An attendant surface low will follow the upper disturbance, tracking from the Minnesota-Iowa border into northern Wisconsin Thursday afternoon and evening. A cold/occluded front will extend southwest from the surface low, crossing southern Wisconsin Thursday evening and night. Forcing from the upper disturbance, as well as lift along the advancing surface front, will support additional shower and thunderstorm potential Thursday afternoon and evening. A few strong to severe storms are possible in the Thursday afternoon/evening activity, in addition to heavy downpours. Whether/not strong to severe storms materialize -- and the spatial extent of the threat if they do develop -- will depend highly on showers/storms moving across the area through the conclusion of the short term & Thursday morning. Winds will turn northwesterly Friday through the weekend as the aforementioned surface low & front push east of the area. Additional scattered showers and thunderstorms are possible Friday through this weekend, though coverage will be more scattered compared to Thursday. Thursday & Thursday Night: Showers and thunderstorms will be in- progress following sunrise Thursday/the beginning of the long term period, pushing east of the area by late morning/early afternoon. Additional shower/storm development is then anticipated along the encroaching surface front during the late afternoon and evening hours. Available mesoscale/CAM guidance suggests sufficient (25-40 knots) effective shear regionally for organized, potentially strong to severe storms in this second round of afternoon/evening development, though potential will depend highly on how much sunshine can occur in the wake of the morning showers/storms. Should sufficient destabilization occur across the region, a few strong to severe storms would be possible. Large hail and gusty winds would be the primary hazards in any strong/severe storms. Heavy downpour potential will continue in Thursday afternoon/evening storms given still elevated PWAT`s in place across southern Wisconsin. Friday Through Sunday: Winds will turn northwesterly as surface low pressure & the Thursday front push east of the region. The upper trough approaching the region Thursday will pass over and east of the region during this timeframe, supporting additional bouts of scattered shower/storm activity. Strong to severe storms appear unlikely at this juncture. Quigley && .AVIATION... Issued 330 PM CDT Tue Aug 13 2024 Light & variable surface winds continue over the open waters through the remainder of today & tonight as a 1020 mb high pressure lingers across the region. The aforementioned high will gradually push east of the lake on Wednesday, allowing prevailing southeast winds to become established. Wind speeds will increase from Wednesday night through Thursday as 1006 mb low pressure develops over the northern Great Plains & eventually approaches Lake Michigan. Gusts will are expected to remain well-below gale thresholds during this period, though a combination of elevated gusts and wave heights is likely to result in Small Craft Advisory conditions in nearshore zones through most of the day on Thursday. Two rounds of showers and thunderstorms are expected from late Wednesday night through Thursday evening. A few storms moving across the open waters Thursday afternoon/evening could become strong to severe, with large hail and gusty winds being the primary concerns. Wind gusts will taper from Friday through the weekend. Additional scattered thunderstorms are possible across the lake during this timeframe, though coverage won`t be as widespread relative to Thursday`s activity. Quigley && .MARINE... Issued 330 PM CDT Tue Aug 13 2024 VFR conditions continue at all southern Wisconsin terminals this afternoon. Developing along the lake breeze, a few scattered showers are evident over portions of the greater Milwaukee metro. Given trends, have inserted a TEMPO -SHRA group through 21Z at KMKE. Will continue to monitor trends for any possible TEMPO extensions at KMKE, as well as any insertions at other terminals. Rain showers will quickly dissipate following sunset this evening. Mostly clear skies and light/variable surface winds prevail overnight. Patchy FG is possible across the region, with the Wisconsin River Valley & low- lying areas being most favored. Have withheld any prevailing mentions in the latest update, but will monitor numerical guidance and observational trends through the overnight period. Prevailing southeast winds will become established on Wednesday afternoon. Quigley && .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