Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
543 FXUS63 KMKX 040915 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 415 AM CDT Thu Jul 4 2024 .KEY MESSAGES... - This Morning: Will be mostly dry into the early afternoon across much of southern WI with temps climbing into the 80s. - This Afternoon: Still cannot rule out brief isolated to scattered showers and thunderstorms (15-45% chances) to develop this afternoon mmainly between 2-7 PM CDT. The greater potential is for areas west and north of Madison. - This Evening: Showers and thunderstorm chances increase through the evening. Areas west of I-39 have the greater chances (50-80%) to see showers/storms between 7-11 PM CDT while areas east of I-39 have lower (10-40%) potential. Early evening storms could produce gusty winds and small hail. - Tonight: Thunderstorm chances gradually diminish after 10 PM CDT, while showers chances (>70%) persist overnight, mainly after midnight into Friday morning. Trends are showing lighter showers and not as widespread of coverage into Friday, but there still remains 50-80% chance through Friday afternoon. - Rainfall today through Friday: Expect widespread totals around a quarter to half and inch, but areas northwest of HWY-151 have a 40- 70% chance for totals to exceed one inch. - Elevated water levels continue on area rivers and streams through the end of the week. Flood Warnings remain in effect in several locations. && .SHORT TERM... Issued 411 AM CDT Thu Jul 4 2024 Today through Tonight: With high pressure gradually sliding eastward this morning, Independence Day will start off dry with light winds. Dry conditions look to persist into the start of the afternoon. Meanwhile an area of surface low pressure over NE/IA this morning begins get its act together through the afternoon as a mid-level shortwave trough sweeps across the northern Plains. Expecting this interaction to deepen the surface low as it tracks into our neck of the woods through the evening. Ahead of this system a stationary front across central WI is progged to become the warm front of the developing low. With the front already north of southern WI, expect the moisture advection to increase through the afternoon across the warm sector with PWATs creeping above 1.5 inches and dewpoints the upper 60s. Instability is also expected to build across the area with SBCAPE nearing 750- 1000 J/kg through the afternoon. However, outside of a minor impulse of mid-level vorticity ahead of the main trough and the surface front strewn across central WI, there is not really a main focus of forcing to initiate convection this afternoon across the warm sector as seen on NAM Nest and the 06z HRRR. Additional given the weak background flow, expecting to see a lake breeze develop this afternoon and push inland, thus stabilizing the environment for areas behind it and limiting the potential development this afternoon. While not overly confident on seeing something development this afternoon, there are still CAMs hinting at some sporadic development through the afternoon and cannot rule out something to develop, mainly for areas west of I-43. If anything does develop, it would likely be brief, pop-up type shower/storm given the lack of deep layer shear and if an outflow from a decaying shower/storm interacts with a nearby storm, it could be the trigger for a stray stronger storm or two capable of producing gusty winds and small hail. Overall, there remains a potential for an isolated thunderstorm this afternoon, but most of southern WI should remain dry through the majority of the afternoon. Same cannot be said for this evening as the shortwave trough pushes into WI aligning the more favorable dynamics and forcing with the ample moisture and instability. The main focus for shower and thunderstorm development this evening will be the surface low deepening to sub-1008mb and cold front extending south from it. Areas west of I-39 will see this activity develop sooner, generally thinking between 00z-04z and with the better forcing, increasing LLJ to around 30 knots aligning with lingering instability, cannot rule out seeing a stronger storm or two capable of producing gust winds. However, the potential remains low, especially if this convection is delayed by a few hours. Otherwise, expect the showers and thunderstorm chances to spread east through the evening with areas east of I-39 seeing things develop a bit late mainly between 02z- 06z. Showers chances persist overnight as the surface low begins to occlude over central WI through Friday. While thunderstorm chances are progged to gradually diminish overnight with the loss of instability, there may be enough MLCAPE for some embedded storms to persist into Friday. As for rainfall, there is a high potential for most areas to pick up to a quarter of an inch of rainfall and any heavier rainfall exceeding a half an inch will likely be associated with the scattered thunderstorms activity. While the thunderstorm activity through this evening looks to be progressive/moves quickly, areas that see repeated/persistent rainfall can pick up locally high amounts exceeding one inch, especially for areas closer to the surface low north of HWY-151. Any additional rainfall to any swollen rivers may contribute to additional rises and localized river flooding. Wagner && .LONG TERM... Issued 411 AM CDT Thu Jul 4 2024 Friday through Wednesday: Will continue to see showers and thunderstorms persist through much of Friday on the back side of departing low pressure. However, the latest medium range models and tail end of the CAM runs show a bit less coverage. Nevertheless, the lingering rainfall on the backside of the low will be lighter in nature given the better forcing shifting east. Should start to see drier conditions Friday night as northwesterly winds develop and bring in a dry airmass. Saturday is looking drier as mid-level ridging sets up over the region and surface high pressure tracks south of the area. Then an active pattern returns for the later half of the weekend into early next week as a series of shortwave troughs traverse the region. The first of these shortwave troughs looks to impact the Upper Great Lakes region Sunday into Monday bringing another shot at showers and thunderstorms. Additional waves are possible into the first half of next week, bringing additional bouts of showers and thunderstorms, but uncertainty due to model differences. Wagner && .AVIATION... Issued 411 AM CDT Thu Jul 4 2024 VFR conditions will prevail through this afternoon with light southerly winds. Expecting a lake breeze to develop and push inland this afternoon, thus resulting in an easterly wind shift for terminals closer to the Lake. Otherwise, may see an isolated shower/thunderstorm develop this afternoon, but confidence on if and where it might develop remains low. Better shower and thunderstorm chances are expected after 00z this evening as low pressure pushes across central WI. Will likely see lower flight condition with any of this activity, which looks to linger into Friday. Wagner && .MARINE... Issued 411 AM CDT Thu Jul 4 2024 Weak high pressure over IL this morning will continue to slide eastward. Winds will remain lighter and vary from the west- southwest to the east through the afternoon. Will see winds begin to pick up into this evening across Lake Michigan as as low pressure coming in from the Central Plains deepens over WI tonight. This low pressure will gradually track eastward across the middle of Lake Michigan into Friday with south-southwesterly winds over the southern half while winds across the northern half will be more north-northeast. These winds will remain fairly breezy with gusts to 20-25 knots. The low will continue to track into eastern Ontario/Quebec for Saturday bringing breezy northwesterly winds across Lake Michigan for Saturday before turn back to the south as an area of high pressure slides up the Ohio River Valley into Sunday. Wagner && .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