Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
650 FXUS63 KMKX 191718 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1218 PM CDT Thu Sep 19 2024 .KEY MESSAGES... - Showers and thunderstorms moving into south central WI this evening then weakening as it moves into SE WI late at night. - More chances for showers and storms Sat nt into early next week. - Cooler temperatures much closer to normal for next week. && .UPDATE... Issued 1217 PM CDT Thu Sep 19 2024 Showers and sct storms over ne IA are within an area of weak low to mid level warm, moist advection and frontogenesis. Much of this activity should dissipate as it approaches south central WI this afternoon via low lvl dry air. Otherwise new convective development is expected over se MN and far nrn IA late this afternoon, as the trailing cold front to the occluded low over Manitoba approaches the area. MLCAPE of 2500 J/KG are expected ahead of the front with the front being aided aloft by the left exit region of a 90 kt jet streak and PVA from a upper wave passage. A sly LLJ and warm, moist advection will increase just ahead of the front to 30-40 kts during this time. The HREF produces a line of deep convection that will begin to weaken after 03Z as it is moving across south central WI. This seems reasonable as MUCAPE quickly drops after sunset with perhaps 1000 J/KG over south central WI but much less to the east. The better upper dynamics also track to the north during this time. Nevertheless expect most locations to see measurable rain tnt but probably fairly light for se WI. The actual cold front will then pass for the morning daylight hours on Fri but only with slight chances for development over ern WI. A drying wly wind and clearing skies will still lead to another day with high temps in the lower to middle 80s. Weak high pressure will then follow for Fri nt with low temps falling back into the 50s. Gehring && .SHORT TERM... Issued 230 AM CDT Thu Sep 19 2024 Today through Friday: Another warm day expected today with mostly clear skies and 925mb temps in the 23-25 C range. This should bring temperatures to the mid to upper 80s for much of the CWA with cooler temperatures near the lake from the expected development of the lake breeze. As we move through the afternoon and especially into the evening hours we will see showers/storms pushing in the from the west as a front pushes in with some PVA aloft helping out. The midlevel moisture and WAA will be sufficient as well in allowing for the potential for storms to push into the area. There is some uncertainty on how early storms might push in but we could see NW parts of the CWA get clipped by some storms in the afternoon. However most of the potential convection is expected into the early to late evening hours. While shear will certainly be sufficient (30-40kts) for severe storms the timing of storms being more in the evening suggests we will quickly lose much of our instability in the evening hours. Thus we could expect some stronger storms to the west, perhaps even some borderline severe storms but as they slide east they will weaken as we move later into the evening. Generally CAMs suggest organized storm activity through the evening and overnight period but they do not show much in the way of stronger storms by the time they push into the western parts of the CWA. Regardless we will watch for potentially strong storms tonight. Into Friday, models suggest the storms and remaining showers will have pushed out of the CWA off to the east though still awaiting the passage of the front which is estimated to come through some time after sunrise Friday morning. The rest of the day Friday looks relatively quiet with clearing skies from the west through the day. Temperatures behind the front will be cooler with highs only expected to reach the low to mid 80s Kuroski && .LONG TERM... Issued 230 AM CDT Thu Sep 19 2024 Friday night through Wednesday: Quieter conditions are expected to continue Friday night through much of Saturday as another brief period of ridging pushes back in with weak high pressure over the area. While some models suggest an earlier arrival in the next system (GEFS), most models suggest that much of Saturday will remain dry with the next system not impacting the region until at least Saturday night into Sunday. This system will be fairly drawn out over the course of a few days with an upper level closed low gradually migrating east northeast from the southwest US on Saturday to the Central Plains by Sunday. However the impacts of this system will be felt further away as the closed low will feature a `wing` of PVA extending eastward toward the CWA. This, in addition to broad developing surface low pressure with some moisture available in the mid levels as well as some WAA may lead to precipitation starting as early as Saturday night with ongoing chances through at least Monday night before the surface low pulls through. Precip chances may linger into Tuesday on the backside of the low before we finally see a return to drier conditions. This system will bring us back to near average temperatures with Sunday featuring the front coming through with broadly high pressure conditions returning by Tuesday with highs the rest of the week likely to be in the low 70s. Plenty of uncertainty with precip chances beyond Tuesday. Some models suggest weak chances for the middle of next week but by the end of the week stronger high pressure should be building into the region in some form. Kuroski && .AVIATION... Issued 1217 PM CDT Thu Sep 19 2024 VFR conditions this afternoon into the early evening. Areas of MVFR Cigs may then develop over south central WI late tnt following the showers and storms. Also cannot rule out patchy fog toward morning west of Madison and especially in the WI River Valley. Any pockets of MVFR Cigs and light fog will burn off within a few hours of sunrise on Fri with VFR conditions by late morning through the afternoon. Gehring && .MARINE... Issued 1217 PM CDT Thu Sep 19 2024 High pressure around 30.0 inches over the lower Great Lakes today will gradually weaken, while low pressure around 29.4 inches tracks northeast across Manitoba, Canada. This will produce light to modest south to southeast winds into Friday. A weak cool front will push southeastward across the open waters Friday evening, bringing scattered showers and isolated thunderstorms from late tonight into Friday evening. Weak high pressure will then settle over the lake for Saturday morning, followed by the passage of a weak wave of low pressure around 29.7 inches for late Saturday night and Sunday. Light to modest southeasterly winds can be expected ahead of this low. Gehring && .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