Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
566 FXUS63 KMKX 271908 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 208 PM CDT Sat Apr 27 2024 .KEY MESSAGES... - Scattered storms are still expected to develop along a weak cold front late this afternoon and evening. A few of these storms may become severe with large hail and damaging winds, but cannot rule out a tornado or two. - Rounds of showers and storms are expected from this evening through late Sun nt. The flash flood threat will remain low but local urban and small stream flooding is more probable. && .UPDATE... Issued 107 PM CDT Sat Apr 27 2024 A Wind Advisory has been issued for east central and far ern WI as the LLJ has been slow to exit. A weakening trend in the pressure and wind fields is expected by late this afternoon. Cumulus to cumulus congestus are lined up along and east of a weak cold front over ern IA to sw WI and the Madison area. Brief convection has been occurring over ern IA into nw IL early this afternoon. Despite shortwave ridging aloft and weakening pressure and wind fields into this evening, the CAMs and current activity suggest convective initiation will occur along the front from mid to late afternoon and evening. MLCAPE will range from 1500-2000 J/kg with effective shear of 30-40 kts during this time. The 0-3 KM hodographs remain fairly straight for any cells on the front but some 0-1 KM clockwise turning is observed east of the front. Thus a small tornado threat remains with better probs for large hail and strong wind gusts. Since the deep layer shear is parallel to the front, a broken line of storms may seed each other resulting in greater pcpn efficiency and a more solid line of storms. At this time the QLCS threat is low as 0-3 km shear is parallel to the front and weakening into the evening. For late evening into the overnight it is possible an area of convection approaching from IA could clip srn WI Gehring && .SHORT TERM... Issued 415 AM CDT Sat Apr 27 2024 Today through Sunday: Early today: Except for a band of light rainshowers currently passing close to Sauk and Marquette counties, dry weather is expected to prevail until this afternoon, with gusty southwest winds rapidly building after sunrise. The strongest wind gusts are expected near Sheboygan and Fond du Lac counties, upwards of 40 mph. Roughly 30 to 40 mph gusts elsewhere. Low pressure around 29.5 inches over northwest Wisconsin will continue to gradually weaken as it moves northeast across Lake Superior into Ontario this afternoon. Gusty south winds are expected across Lake Michigan today, with a few gusts approaching or reaching gale force, especially in the northeast portion of the lake. Winds will then gradually shift from southwest to northerly tonight as a cold front tracks south, but southerly winds will continue over far southern Lake Michigan as the front stalls. Brisk northeast winds will then prevail over central Lake Michigan on Sunday with lighter winds in the north, and variable winds in the south where the stalled front remains. Modest east to southeast winds will then develop over all of the lake Sunday night as the stalled front moves north as a warm front. Brisk east winds, possibly reaching gale force, are expected over the northern tip of the lake late Sunday night into Monday morning. Breezy south winds will develop over the remainder of the lake on Monday. Rounds of showers and thunderstorms are expected tonight into Monday morning. A few of these storms could produce locally gusty winds and hail. This afternoon / evening: Storms are expected to develop along a southwest to northeast oriented frontal boundary, perhaps as early as 1 PM or as late as 7 PM today. CAMs currently depict the position of convective initiation as a line from Monroe WI to Sheboygan WI, with roughly one or two counties distance east/west disagreement in positioning. Forecast soundings indicate southwest winds throughout the column, with unidirectional shear, yet impressive helicity integrals. HREF Mean MUCAPE south of the boundary exceeds 2000 j/kg, with a surface-based effective inflow layer. HREF mean STP exceeds 2.0, with some models (esp. the Nam NEST) pushing 3.0. This parameter space would suggest an environment capable of all SVR hazards (hail, damaging winds, and possibly tornados). Localized heavy rainfall is a concern, especially if storms along the front affect the same area multiple times. The best agreement in model QPF is positioned along and south / southwest of the I-94 corridor. Late tonight through Sunday: Instability is progged to decline late tonight. Some models depict a lull in shower / storm activity late tonight, while others depict wider storm coverage with weaker intensity. Severe wx potential does continue into Sunday, but with HREF mean MUCAPE less than 1000 j/kg (even with the compliment of daytime heating), this is looking like the less active day of the two. That said, the positioning of the warm front leaves much in question in the way of instability. Regardless of severe wx potential, localized heavy rainfall seems equally probable on Sunday, with model QPF evenly split between the two rounds of activity. Sheppard && .LONG TERM... Issued 415 AM CDT Sat Apr 27 2024 Sunday night through Friday: Synopsis: The upper trough ejecting into the Northern Plains on Sunday afternoon/the conclusion of the short term period will progress toward the Canadian bLow pressure around 29.5 inches over northwest Wisconsin will continue to gradually weaken as it moves northeast across Lake Superior into Ontario this afternoon. Gusty south winds are expected across Lake Michigan today, with a few gusts approaching or reaching gale force, especially in the northeast portion of the lake. Winds will then gradually shift from southwest to northerly tonight as a cold front tracks south, but southerly winds will continue over far southern Lake Michigan as the front stalls. Brisk northeast winds will then prevail over central Lake Michigan on Sunday with lighter winds in the north, and variable winds in the south where the stalled front remains. Modest east to southeast winds will then develop over all of the lake Sunday night as the stalled front moves north as a warm front. Brisk east winds, possibly reaching gale force, are expected over the northern tip of the lake late Sunday night into Monday morning. Breezy south winds will develop over the remainder of the lake on Monday. Rounds of showers and thunderstorms are expected tonight into Monday morning. A few of these storms could produce locally gusty winds and hail.order Sunday night into early Monday morning. The advancement of the upper wave will support surface low placement along the MN-WI border vicinity by sunrise Monday, with a cold front forecast to be extending southwest into the Central Plains. The upper trough will progress across Lake Superior during the day on Monday, gaining separation from its attendant surface cyclone in the process. This will promote gradual filling of the surface low over northern WI and the Upper Peninsula of MI Monday afternoon, with the associated cold front crossing & ultimately exiting the region during the evening hours. The advancing upper wave & surface front will support additional periods of showers and embedded thunderstorms from Sunday night through Monday afternoon. Westerly surface flow will usher a drier/Canadian air mass into the state Monday night, with winds quickly turning back out of the south from Tuesday into the middle portions of next week. Occurring in response to an upper jet/trough pairing approaching from the Northern Plains, said southerly flow will allow moisture to return to the area on Tuesday afternoon. Additional showers and storms will be possible Tuesday night through Wednesday as a surface low related to the upper trough/jet tracks across Ontario & pulls a cold front across the state. The boundary is likely to stall out somewhere to our south & east during the Thursday/Friday timeframe, with considerable spread in placement evident in current deterministic & ensemble-based guidance. Sunday Night & Monday: Anticipate periods of showers and embedded thunderstorms. While depicting plenty of shear through the column, available forecast soundings show only weak (<500 J/kg) MUCAPE through the majority of this timeframe, suggesting low overall strong/severe storm potential in this activity. Will nevertheless monitor trends over the coming cycles, as a slower FROPA on Monday PM would allow for instability & isolated strong/severe potential to trend up. Tuesday Night & Wednesday: Expect another round of rainfall during this portion of the period. Early progs show some signal for CAPE to work into the area, which has justified continued mentions of thunder in the overnight weather grids. It remains too early to comment on any stronger storm potential, though trends will continue to be monitored. Thursday & Friday: Forecast uncertainty jumps up considerably during this portion of the period, as area weather is likely to be influenced by where the mid-week frontal boundary ultimately stalls. Additional rainfall chances would be possible in the scenario that the feature lingers further north than currently progged. Will continue to adjust the late week forecast as boundary placement clarifies. Quigley &&Low pressure around 29.5 inches over northwest Wisconsin will continue to gradually weaken as it moves northeast across Lake Superior into Ontario this afternoon. Gusty south winds are expected across Lake Michigan today, with a few gusts approaching or reaching gale force, especially in the northeast portion of the lake. Winds will then gradually shift from southwest to northerly tonight as a cold front tracks south, but southerly winds will continue over far southern Lake Michigan as the front stalls. Brisk northeast winds will then prevail over central Lake Michigan on Sunday with lighter winds in the north, and variable winds in the south where the stalled front remains. Modest east to southeast winds will then develop over all of the lake Sunday night as the stalled front moves north as a warm front. Brisk east winds, possibly reaching gale force, are expected over the northern tip of the lake late Sunday night into Monday morning. Breezy south winds will develop over the remainder of the lake on Monday. Rounds of showers and thunderstorms are expected tonight into Monday morning. A few of these storms could produce locally gusty winds and hail. .AVIATION... Issued 120 PM CDT Sat Apr 27 2024 Sct-bkn035-045 cumulus and cumulus congestus this afternoon and evening with scattered to numerous storms developing over srn WI. The passage of a cold front late tonight will then result in a moist enely flow and low stratus development. MVFR Cigs will develop by early morning Sunday then fall below 1 kft for the remainder of the day. Some fog development will also occur during this time. Rounds of showers and storms will also continue on Sunday. Gehring && .MARINE... Issued 120 PM CDT Sat Apr 27 2024 Low pressure around 29.5 inches over northwest Wisconsin will continue to gradually weaken as it moves northeast across Lake Superior into Ontario this afternoon. Gusty south winds are expected across Lake Michigan today, with a few gusts approaching or reaching gale force, especially in the northeast portion of the lake. Dense fog had formed over portions of nrn Lake MI but has since dissipated. Will keep the Dense Fog Advisory in effect for nrn Lake MI as the fog may redevelop late today and this evening. Winds will then gradually shift from southwest to northerly tonight as a cold front tracks south, but southerly winds will continue over far southern Lake Michigan as the front stalls. Brisk northeast winds will then prevail over central Lake Michigan on Sunday with lighter winds in the north, and variable winds in the south where the stalled front remains. Modest east to southeast winds will then develop over all of the lake Sunday night as the stalled front moves north as a warm front. Brisk east winds, possibly reaching gale force, are expected over the northern tip of the lake late Sunday night into Monday morning. Breezy south winds will develop over the remainder of the lake on Monday. Rounds of showers and thunderstorms are expected tonight into Monday morning. A few of these storms could produce locally gusty winds and hail. Gehring && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Wind Advisory...WIZ051-WIZ052-WIZ059-WIZ060-WIZ065-WIZ066- WIZ071-WIZ072 until 4 PM Saturday. LM...Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ868 until 1 AM Sunday. Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 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