Expires:No;;055447 FXUS63 KMKX 120306 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1006 PM CDT Sat May 11 2024 .KEY MESSAGES... - Warm on Sunday, with scattered showers and thunderstorms. Storms may initiate as early as the mid afternoon, but coverage should be highest in the evening hours due to an approaching cold front. Rain chances continue Monday. - Additional rain chances middle to end of the week. && .UPDATE... Issued 1000 PM CDT Sat May 11 2024 Diurnal cumulus clouds have eroded rapidly, leaving skies mostly clear. GOES is tracking an arc of thin and scattered high altitude clouds from northwestern WI through central WI, but these shouldn't have much of an impact for folks viewing the northern lights, given the thin and dispersed texture. A gradual increase in cloud coverage may occur after 2 AM, hence between now and then is the best window for sky viewing. For the Sunday mid-afternoon through evening/night thunderstorm setup, forecast soundings show deep inverted-v signatures, with 20 to 30 kts of deep shear (which may support clusters or line segments, but not supercells) with high LCL heights. The main triggering mechanism for convection appears to be the SW to NE oriented cold front sagging southward into our CWA Sunday evening, but some CAMs are beginning to hint at prefrontal initiation in the mid to late afternoon. Hence, the highest storm coverage and rain chances are in the evening hours (as the front approaches), with more isolated activity possible in the afternoon. Instability is only marginally favorable for severe weather (1000 joules or higher in some models with sfc dewpoints well over 50 F, less than 1000 joules for models with upper 40s to low 50s dews as currently forecast), hence few (if any) storms are expected to reach severe criteria. If storms over-perform, wind gusts would be the primary threat. Storms that initiate in advance of the front (afternoon) may have enough CAPE for a hail threat as well. Sheppard && .SHORT TERM... Issued 242 PM CDT Sat May 11 2024 Rest of this Afternoon through Sunday night: Scattered showers will continue to impact the lakeshore areas mainly north of Milwaukee through this afternoon, within an area of deeper moisture and cyclonic flow. Elsewhere, scattered to broken fair weather cu will persist through late afternoon, before dissipating this evening. Winds will remain breezy from the northwest. High pressure builds into the region this evening, which should result in a period of mostly clear skies, along with light winds. Temperatures are expected to fall into the mid to upper 40s, before leveling off and then slowly rising toward sunrise as warm advection increases across the region, which will also result in an increase in mid and high level clouds. An area of showers and a few thunderstorms associated with the warm advection will develop over northern Wisconsin, but should remain north of the forecast area through Sunday morning. Warm temperatures are expected on Sunday, with gusty southwest winds helping to boost highs into the upper 70s and low 80s. A weak frontal boundary will begin to sink southward into the region during the afternoon hours, setting off scattered showers and thunderstorms. A number of places may remain dry, and those that do see a shower/storm shouldn't expect the rain to last too long. Rain chances will persist into the late evening as the weak boundary pushes south, before coverage wanes late Sunday night. Boxell && .LONG TERM... Issued 242 PM CDT Sat May 11 2024 Monday through Saturday: The aforementioned frontal boundary will settle into northern Illinois by early Monday. Lift will increase across the boundary Monday and Monday evening ahead of a shortwave moving across the central Plains, aided by the right entrance region of a strengthening upper jet over the UP and eastern Ontario. This should result in several rounds of showers and thunderstorms across southern Wisconsin, with the greatest concentration along and south of I-94. Highs will be a touch cooler, topping out in the low to mid 70s. High pressure will nose in from the north on Tuesday and Wednesday, with cooler north to northeast flow and dry weather expected. Another series of shortwaves look to affect the region Thursday and/or Friday, with increasing rain chances. Boxell && .AVIATION... Issued 1000 PM CDT Sat May 11 2024 VFR conditions continue tonight, with mostly clear skies (high altitude clouds) and winds light and variable. Light south winds at sunrise veer southwest late Sunday morning, with gusts upwards of 20 kts in the afternoon. A cold front sagging southward into the region Sunday evening will lead to gradually increasing shower and thunderstorm coverage, with cumulonimbus bases at roughly 5,000 to 10,000 ft. Storms firing in advance of the front (as early as mid afternoon Sunday) cannot be ruled out. Sheppard && .MARINE... Issued 242 PM CDT Sat May 11 2024 Northwest winds will become light and variable tonight as weak high pressure moves across the lake. The high will shift east early Sunday morning while a wave of low pressure and its associated cold front moves across northern Lake Michigan Sunday night. This will result in breezy southerly winds on Sunday shifting to northerly and weakening late Sunday night. The cold front will move south on Monday bringing light to modest northerly winds to the entire lake. High pressure is then expected to move across the Great Lakes Tuesday and Wednesday. Winds will be from the north during this time. Gusty north winds may reach Advisory levels on Tuesday. Boxell && .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