Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
769 FXUS63 KMKX 221509 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1009 AM CDT Sat Jun 22 2024 .KEY MESSAGES... - Flood Watch continues for flash flooding potential across portions of south central and southeast Wisconsin through late this evening. Multiple additional rounds of showers and storms are expected, with widespread rainfall amounts between 1 and 3 inches and locally higher amounts exceeding 3 inches. - There is the potential for strong to severe thunderstorms this afternoon/evening (risk 2 out of 5). Damaging winds are expected to be the primary hazard, with isolated tornadoes and a few areas of large hail possible. - Heat index values in the upper 80s to low 90s are expected across far southern Wisconsin today, with heat index values reaching 90 degrees across much of southern Wisconsin again on Tuesday. - Strong thunderstorms may develop once again along a cold front on Tuesday. && .UPDATE... Issued 950 AM CDT Sat Jun 22 2024 Broad line of showers with a few rumbles of thunder embedded within it continue to work its way west to east across the CWA this morning. May see coverage shrink as it pushes east based on the last reflectivity trend, but timing the back edge of the showers looks to push east over the lake between 16-18z. Behind this activity visible satellite imagery does show some breaks in the clouds and could see some broken sunshine. This trend favors the environment to recover behind the morning showers and destabilize with the SBCAPE of 1000-2000 J/kg within reach. Thus, continue to monitor for flooding and severe potential this afternoon and evening. However trends in the incoming morning model runs give a bit more uncertainty as the upper-level dynamics seem a bit more offset compared to previous days. While WI looks to remain between the left exit and right entrance region of two upper- level jets, the double barrel mid-level shortwave trough with mid-level ridge in between might limit things this afternoon. Also the building LLJ looks to ramp up a bit later and further south than previous days. Also the surface low is more broad and not as strong over west central WI. While the alignment may be a bit more offset, the forcing still remains in place to support convection. The other factor in today`s afternoon/evening potential is where will the warm front set up. Current obs plot the boundary across our northern tier of the CWA with dewpoints in the 70s already. Some of the 12z CAMs such as the HRRR have the warm front not making it much farther north and even hint at it pushing a bit south more toward the I-94/HWY-18 corridor, which when convection develops may orientated more west to east along the warm front. This scenario would lend more to our flash flooding threat given storms training over the same area and where we received plenty of heavy rainfall yesterday before pushing south. But still could see wet microburst embedded within the line given the high PWATs. The other scenario is the front continues to lift north bringing the west to east orientated convection across east central WI, which would give areas further south more time in the warm sector and bring a northeast to southwest orientated cold front boundary across the area this evening. This scenarios also seems to lean more with a late afternoon initialization as seen in the 12z NAMnest and bring more of QLCS type line across the area, which would have better severe damaging winds and a few embedded tornadoes potential. Overall, will need to monitor and see which direction the environment trends. As of now I do lean a bit more toward the solutions with a late afternoon initialization giving the ongoing showers, current placement of the boundary, and a bit of mid-level ridging progged to build into the area. Nevertheless, stay up to date with the latest forecast and be prepared to at minimal see heavy rainfall and thunderstorms this afternoon. Wagner && .SHORT TERM... Issued 500 AM CDT Sat Jun 22 2024 Today through tonight: Scattered showers and thunderstorms are ongoing along the nose of an 850 mb LLJ, pushing northeastward through the mid-morning hours. Warm frontogenesis north and west of the I-90/I-94 corridor will allow for scattered to isolated showers and storms to linger through the day, while areas to the south may even see brief breaks in cloud cover and temperatures rising into the upper 80s in far southern Wisconsin. With high humidity, heat index values in far southern Wisconsin may rise to near 90 degrees. PWATS of 2 to 2.25 inch will lead to heavy rainfall rates and wet microburst potential within any thunderstorms that develop. However, storms will be moving quickly northeastward. Therefore, training convection will be needed to realize flash flooding potential. A Flood Watch remains in effect due to multiple additional rounds of rainfall over already wet soils. This watch is valid through midnight CDT tonight to account for any lingering precipitation after cold frontal passage. Low pressure strengthens over northern Wisconsin late this afternoon, developing and pushing a strong cold front southeastward through southern Wisconsin late this afternoon into tonight. This cold front will be pushing into a primed airmass with CAPE of 1000 to 2000 J/kg, 0 to 3 km SRH of 200 to 300 m2/s2, and minimal CIN. PWATs on the order of 2 inches, a 700 mb jet, and at least a few hundred J/kg of DCAPE lends credence to widespread damaging wind potential along the line. QLCS tornadoes are also a potential as line normal shear may be up to 40 kts in places while SRH of 200 to 300 m2/s2 continues. Storms exit offshore into Lake Michigan into the early overnight hours, with northwesterly breezes thereafter. MH && .LONG TERM... Issued 500 AM CDT Sat Jun 22 2024 Sunday through Friday: A quiet day on Sunday, with a few isolated showers and thunderstorms in southeastern Wisconsin during the afternoon hours (15% chance) as a shortwave passes through. Northwesterly breezes continue, with highs near 80 degrees. High pressure then dominates through Monday, allowing temperatures to rise again into the mid-80s. Tuesday, low pressure propagating eastward through the Canadian provinces will shift winds southwesterly and bring in high heat index values and high humidity once again. A frontal feature associated with this low is expected to bring showers and thunderstorms. A few storms may be strong to severe, with increasing CAPE and PWATs through the day. Longwave ridging across the Southeast U.S. and Appalachia may permit the frontal boundary to stall through Wednesday morning before weakening, bringing additional rainfall to southern Wisconsin. High pressure and seasonable temperatures are then expected Wednesday through late week, with an additional Canadian low producing thunderstorm chances Friday. MH && .AVIATION... Issued 1000 AM CDT Sat Jun 22 2024 Line of scattered showers and thunderstorms working there way across southern WI through the remainder of the morning. They are bringing lower visibilities and ceilings MVFR to IFR. Areas with heavier showers/thunderstorms, such as SBM and JVL are experiencing the more restricted flight conditions. Expect this activity to continue to push east over Lake Michigan between 16z-18z. Then VFR with some pockets of MVFR conditions expected behind this through the early afternoon with a few breaks in the clouds. Then this afternoon and evening expecting additional shower and thunderstorm to develop and track across southern WI through 00z-04z. Accompanying any storms will not only be lower flight conditions, but also heavy rainfall, brief strong, gusty to damaging winds, and cannot rule out even some hail or an isolated tornado or two. Overnight these showers and storms will push east and northwesterly winds develop behind the cold front into Sunday as high pressure builds into the region. Wagner && .MARINE... Issued 500 AM CDT Sat Jun 22 2024 Light winds will transition to southerly and gusty across the southern two-thirds of the open waters and to easterly and gusty across the northern one-third this morning into this afternoon as low pressure develops in southern Minnesota. This low will progress through northern Lake Michigan this evening into tonight, bringing widespread thunderstorms along a cold front. Gusty winds are expected with these thunderstorms, especially in the southern half of the lake. Winds may approach Small Craft Advisory criteria tonight after the line of storms moves into the open waters. Winds across the Lake then shift northwesterly late tonight into Sunday morning as storms end. Winds will diminish but remain northwesterly through Sunday night, with high pressure building in Monday and producing light and variable winds. MH && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058- WIZ059-WIZ062-WIZ063-WIZ064-WIZ065-WIZ067-WIZ068-WIZ069 until midnight Sunday. 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