Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
938 FXUS63 KMKX 231842 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 142 PM CDT Mon Sep 23 2024 .KEY MESSAGES... - Showers for se WI on Tue with at least a small potential for heavy rainfall rates over far se WI. - Mild and Dry conditions for Wed-Fri. && .UPDATE... Issued 142 PM CDT Mon Sep 23 2024 Middle to high clouds will increase from the south late this afternoon into the evening as a shortwave trough over srn IA lifts nwd through srn WI. High based elevated instability may lead to some virga or even sprinkles this evening. Farther to the west a 110 kt nly jet streak will dig a shortwave trough from the nrn Great Plains to the IA/MO border by 00Z Wed. This will kick the shortwave trough over KS and weak low over srn MO newd on Tue. There are differences on the track of the low but the main positioning would take the low and upper wave across nrn IN into south central lower MI. This would bring PWs over an inch into far se WI with near saturation up to 10-15 kft possible. Frontogenesis in the sfc-850 mb layer cloud trigger some narrow bands of mdt to even heavy rainfall, but overall confidence is low in actual occurrence. A farther srn track like the NAM would greatly limit rainfall coverage while a more nrn track like the ECMWF would bring higher confidence for heavy rainfall rates in se WI. At this time will forecast 60-70 percent chances for showers from MKE south to ENW with smaller probs for heavy rainfall rates. The showers may then linger into Tue nt over far se WI. Gehring && .SHORT TERM... Issued 410 AM CDT Mon Sep 23 2024 Today and Tonight: Cooler temperatures, drier air and mostly clear skies are in store for much of southern Wisconsin today. With the cold front to our east in Michigan and Indiana, a drier air mass will move into the state bringing dewpoint temperatures in to the mid 40s to low 50s. With the light winds away from lake Michigan and the clear skies, there is a small chance for some fog to develop early this morning prior to sunrise. The best chances for fog to develop will be in the northwestern corner of our forecast area, particularly in the low lying areas. The window for this fog to develop will be small as were looking for the dew point depression to be at or near zero before the drier air mass begins to move in. Outside of this, the beach hazard statement and high swim risk remains in effect for southern Wisconsin beaches through this afternoon (into this evening for far southeastern Wisconsin). This is due to the north to northeast gusty winds and building waves. The tighter pressure gradient over the Lake will eventually shift and weaken, which will cause the waves to diminish later today. The chance for rain returns to southern and eastern Wisconsin tonight into Tuesday. A low pressure system will move from the mid Mississippi valley and is expected to pass near the southern portion of Lake Michigan. There is still a bit of uncertainty on the track of this low pressure system. The difference in track is how far to the south will this low pass. Keep POP chances low with the with 40% chance being the max across far southeastern Wisconsin during the early morning hours Tuesday. There will be a brief period of east winds expected, which should help with some moisture advection that wraps around the low. Otherwise the better chances for rain and thunderstorms is expected to stay to the south. Patterson && .LONG TERM... Issued 410 AM CDT Mon Sep 23 2024 Tuesday through Sunday: As the low pressure system moves out of the southern Great Lakes Region, guidance has it interacting with a Canadian surface high. This would likely slow down the forward progression of the low pressure system causing it to linger a bit over Lake Michigan and far eastern Wisconsin. So low chance POPs around 15% are expected to persist into Tuesday evening. After this low pressure system exits, the Rex Blocking Pattern is expected to set up across the Central CONUS. This pattern will then dominate through much of the week. This pattern would keep Wisconsin dry and slightly warmer with highs slightly above normal in the mid to upper 70s. Uncertainty returns for the weekend as long term guidance suggests a tropical system advecting northward out of the gulf and interacting with the center low pressure system of the Rex Blocking Pattern. If these two low pressure systems due interact, its likely that the Fujiwara effect would take over and cause them to rotate around the center point (kind of looks likes its rotating around each other for those who are less familiar with this effect). This brings in a lot of uncertainty on the track and how this would break down the blocking pattern. Especially when the strength of the system coming out of the gulf would be a key factor. Kept to the average among guidance which introduces some low chance POPs around 30% or less for the weekend. Patterson && .AVIATION... Issued 142 PM CDT Mon Sep 23 2024 Sct-bkn035 cumulus this afternoon then lingering over far ern WI into the evening. Patchy fog will develop in low lying areas of south central WI late tnt. Farther east, MVFR Cigs will move from Lake MI well inland during the early morning hours of Tue and remain over ern WI throughout the day. Areas of Cigs below 1 kft and vsbys of 2-5SM BR are expected especially near the lake. The intermittent showers will contribute to the reduced vsbys at times. Gehring && .MARINE... Issued 142 PM CDT Mon Sep 23 2024 Modest north to northeast winds will persist through this afternoon as low pressure around 29.9 inches over the lower Great Lakes continues toward the New England States. Meanwhile high pressure around 30.1 inches over Lake Superior and northern WI will move just slightly eastward. Low pressure around 29.7 inches then track from southern IL to southern lower MI on Tuesday while surface ridging remains over Lake Superior. This will maintain modest east to northeast winds to the lake. The winds will then shift northerly for Tuesday night and Wednesday as the low moves away. A Small Craft Advisory will expire this afternoon as winds and waves continue to subside. Gehring && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Beach Hazards Statement...WIZ071-WIZ072 until 4 PM Monday. LM...Small Craft Advisory...LMZ645-LMZ646 until 4 PM Monday. && $$ 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