Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
184 FXUS63 KMKX 191954 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 254 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. && .SHORT TERM... Issued 253 PM CDT Thu Sep 19 2024 Tonight through Saturday: Deep convection has formed a little early along the IA/MN border and is oriented w-e and moving newd with the mean flow. This may have been triggered by low to mid level warm advection, but additional n-s convective development is expected over that region late this afternoon, as a cold front approaches the area. MLCAPE around 2500 J/KG is in place 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 into Sat with low temps falling back into the 50s but highs once again in the 80s. Gehring && .LONG TERM... Issued 253 PM CDT Thu Sep 19 2024 Saturday night through Thursday: High pressure will move east of the area with swly flow aloft becoming established into early next week. A series of shortwave troughs including a passing wave of low pressure for Sat nt-Sun will bring rounds of showers and storms to the region. However the amounts are in question and a precipitation gradient from north to south is expected. 1 inch amounts will be possible over far srn WI during this time. A shortwave trough may dig swd from Canada for mid week keeping slight chances for showers in the forecast. Cooler temps, much closer to normal, are expected for this period. Gehring && .AVIATION... Issued 253 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 253 PM CDT Thu Sep 19 2024 High pressure around 30.0 inches over the lower Great Lakes 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