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Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
050 FXUS63 KMKX 011506 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1006 AM CDT Mon Jul 1 2024 .KEY MESSAGES... - River flooding and high water levels continue this week. Additional rises will be possible with any heavier rainfall (late tonight through Tuesday night). - Thunderstorm chances late tonight through Tuesday night. - Warmer / quiet weather expected Wednesday. - Shower and thunderstorm chances return Thursday and Friday. && .UPDATE... Issued 1005 AM CDT Mon Jul 1 2024 The latest model guidance continues to indicate that shower / storm activity will hold off until late tonight (past midnight), with more widespread shower / weak thunderstorm coverage arriving early Tuesday morning. Some CAMs are hinting at a mid-Tuesday lull in convective activity, allowing southerly flow to destabilize the environment for a heavier round of afternoon / evening rainfall. Other CAMs prefer more continuous scattered shower / storm coverage. Either way, the rainfall from this event will likely be our main concern, with 4 rivers already in flood stage and more likely to rise as this event gets underway. Widespread 1 to 2.5" rainfall amounts are currently forecast between tonight and 7 AM Wednesday, trends will be monitored as we go into the next forecast iteration. CAMs and forecast soundings show MUCAPE 1000 joules at best, much less for the majority of the event. Widespread severe weather appears unlikely at this time, but some showers may evolve into weak thunderstorms. If any stronger storms were to occur, wind gusts and small hail would be the concerns. The cold front passing Tuesday night will continue the shower / storm chances as it rolls through. Still expecting it to exit the region around 7 AM CDT Wednesday, leaving mostly dry weather behind it. CAA behind the front is generally weak (winds due west instead of northwest), allowing ample solar heating to boost daytime high temps to the 80s on Wednesday, perhaps even the upper 80s east of the Kettle Moraine. Sheppard && .SHORT TERM... Issued 406 AM CDT Mon Jul 1 2024 Today and Tonight: High pressure to the east of Wisconsin will continue its trek east throughout the day. Skies will remain clear with light and variable through mid morning when southeasterly wind begin to pick up. There is a small chance for some fog to develop early this morning. While skies will be clear and winds light, dewpoint depressions are still a bit to high. Fog development in the summer needs a very saturated environment where air temperatures and dewpoints temperatures are very close together. This means the dewpoint depression will need to be very close to zero degrees if not zero to achieve fog development. Low lying areas, river valleys, and marsh lands will have the best chance for fog development but even still thats around a 20% chance or less. As the high pressure system moves east, a low pressure system will be advancing from Alberta and Saskatchewan. This low pressure system will stay north of the state and eventually swing northeast toward James Bay Tuesday. The pressure gradient will slowly tighten throughout the afternoon and evening resulting in some increasing southeast winds. By Monday night, the last of the large scale subsidence will pull out of the state. Conditions are expected to remain dry through midnight across southern Wisconsin, but with a low pressure system right on the heels of this exiting high pressure rain chances will begin to increase heading into Tuesday morning. This low pressure system slowed down a bit which has resulted in the latter arrival of POPs to Tuesday morning. Patterson && .LONG TERM... Issued 406 AM CDT Mon Jul 1 2024 Tuesday through Sunday: As the approaching low pressure system swings through the northern Great Lakes Region Tuesday on its eventual trek toward James Bay, POP chances will gradually increase. The biggest change between the previous model runs is that this system as a whole looks to slightly slow down which means POPs wont start increasing until early Tuesday morning. Sustained south to southeasterly winds will bring warm moist conditions to the forecast area ahead of this low pressure system essential prepping the environment for rain. As the surface low advances through the northern Great Lakes Region, the low looks to become vertically stacked which will cause the system to briefly strengthen before occluding. As this system strengthens, a LLJ is expected to develop and move into the state. The timing and placement of this LLJ is still a bit uncertain which leads to a short period of broad brushed POPs through the afternoon. Rain chances Tuesday morning and afternoon will be much more conditional on the warm moist air and mesoscale forcing (LLJ or effective warm front) all coming together to produce rain/storms. As things stand now south western and west central Wisconsin look to have the best chances for rain to develop during the day. Heading into Tuesday evening/overnight the low pressure system looks to pull northeast and head towards James Bay. As it moves northeast a cold front will be dragged across the state. This will provide a much better forcing mechanism and higher chances for rain across all of southern Wisconsin. Given the uncertainty in the morning storm potential there is also uncertainty in the strong to severe thunderstorm potential. On the flip side there is much higher confidence in the potential for moderate to heavy rain. PWATs are expected to be climbing with values approaching 2 inches by Tuesday evening. With some elevated river flow and a few rivers still in minor flood any training storms could potentially cause flooding concerns. Wednesday, weak high pressure will briefly move through the state keeping conditions dry through the day before another trough advances toward Wisconsin. This low pressure system looks to advance from the northern plains and move through the state Friday. This is a pretty significant change from roughly 24 hours ago when guidance suggested this trough would move through on the 4th of July (Thursday). Uncertainty in the timing of this system remains, but trends are looking better for daytime celebrations. Thursday night into Friday will be the time frame to keep an eye on. At this time the GFS and Canadian seem to the the slower solutions, potentially hinting at the 4th remaining dry while the Euro seems to be a bit faster. The active pattern remains through the rest of the extended. Persistent WAA through the extended will keep temperatures up with many days expected to see highs in the upper 70s to mid 80s. Patterson && .AVIATION... Issued 1005 AM CDT Mon Jul 1 2024 VFR conditions continue and light southeast winds develop today as the high pressure system departs eastward. High clouds gradually approach today, with showers likely to hold off until after midnight tonight. Cloud ceilings are currently expected to lower from around 10 kft towards 4kft overnight through Tuesday AM, generally preserving VFR cigs until Tuesday afternoon. Rain shower coverage in the region is expected to gradually increase throughout said period, and some thunderstorms (likely weak) may accompany the showers. Southeast winds accelerate and veer south gradually. Though a lull in shower / storm coverage mid Tuesday is possible, additional showers and thunderstorms are expected along and ahead of an approaching cold front, resulting in lower cloud cigs. Shower and storm chances continue until around 7 AM CDT Wednesday, when the front moves clear of the area. West winds and drier weather expected behind the front. Sheppard && .MARINE... Issued 406 AM CDT Mon Jul 1 2024 Weak winds early this morning will be light and variable across the northern half of the lake while the southern half will have predominately light easterly winds. The lighter winds through mid morning will be due to high pressure around 30.3 inches moving overhead. High pressure will continue moving east until it exits the western Great Lakes Region Monday night. Winds will become southeasterly and increase as low pressure around 29.4 inches moves northeast from Saskatchewan toward James Bay. Winds will remain south to southeasterly until Tuesday night when a cold front crosses the lake. Rain and thunderstorms are expected with the frontal passage. Southwest to west winds are expected behind the front. Weak high pressure returns to the region Wednesday night into Thursday bringing a return of light and variable winds. Patterson && .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