Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
935 FXUS63 KMKX 211602 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1102 AM CDT Fri Jun 21 2024 .KEY MESSAGES... - Flood Watch for flash flooding potential for portions of south central and southeast WI from this afternoon into early Saturday evening. Multiple rounds of showers and storms are expected with rainfall amounts between 1-2 inches and locally higher amounts exceeding 2 inches, especially for areas west of I39/90 corridor. - Strong to severe thunderstorms will be possible from this afternoon through Saturday evening as multiple rounds of storms are expected. Damaging winds is the main hazard. && .UPDATE... Issued 1045 AM CDT Fri Jun 21 2024 Main driver of our active weather will the the warm frontal boundary and how far north it will lift through the afternoon. This will determine where the storms this afternoon will set up and train resulting in heavy rainfall and flash flooding potential. The latest model trends are hinting a slower northward progression and may set up the boundary and flooding potential a bit further south. May need to match the trend for the Flood Watch and bring toward the WI/IL west of Rock Co. Otherwise, currently the effective warm front is strung across the southwest corner of the CWA with elevated storms north of it across west central WI. Currently tracking the outflow on the southern end of this activity across northeast IA and looks to be enough forcing to ride along the effective frontal boundary and northern edge of the instability with SBCAPE around 1000 J/kg to trigger a few storms late this morning early afternoon. However, the stratus deck ahead of it may be enough to subdue this activity, but as we get more into day instability will build and erode the cap a bit more. Wagner && .SHORT TERM... Issued 447 AM CDT Fri Jun 21 2024 Today through Saturday: Cyclogenesis over CO today will attempt to move the warm front, currently extending ewd across NE, IA and nrn IL, northward into srn WI this afternoon into the evening. A modest swly LLJ of 25-30 kts and thetae advection is expected to develop ewd toward central WI within an airmass of PWs of 1.80-2.00 inches. The HREF takes the MCS over far nw IA and srn MN into srn WI this afternoon via Corfidi vectors and the thermal wind. Pcpn efficiency should be rather high given the aforementioned high PW airmass, warm cloud layer around 4 KM, and relatively high RH in the low to mid levels of the ATM. Training convection will be possible into the evening and thus issued a Flood Watch for portions of srn WI. The Flood Watch will continue into Sat-Sat evening to account for multiple rounds of showers and storms Sat-Sat eve. This will be supported by an approaching wave of low pressure along the warm front and aloft. A well organized swly LLJ of 40 kts will provide plenty of moisture transport from early Sat AM into the early evening, maintaining PWs of 2 inches or more. Multiple rounds of lines and cluster of storms are expected. The wind shear is a bit more organized on Sat than today, but a damaging wind threat from line segments is the main hazard for both days other than the flash flooding. Gehring && .LONG TERM... Issued 447 AM CDT Fri Jun 21 2024 Sunday through Thursday: Low pressure exits to the east on Sunday, although 00Z runs of global models indicate potential for a few showers lingering behind the surface low. Still, northeasterly winds will bring in a brief cool down to seasonable temperatures Sunday, before winds shift back to southerly on Monday as longwave ridging builds from the central Plains into the Upper Midwest. A strong surface low propagating along the northern edge of this ridge will drag a cold front through the Upper Midwest on Tuesday, also bringing showers and storms along it. Ahead of this system, WAA with plenty of moisture and an 850 mb jet may produce showers and thunderstorms overnight Monday into early Tuesday morning. Temperatures may leap back into the upper 80s on Tuesday depending on the timing of the cold frontal passage, with Wednesday being significantly cooler as the system breaks down the northern edge of the ridging. Northwesterly flow remains predominant through the end of the week, keeping temperatures seasonable. MH && .AVIATION... Issued 1050 AM CDT Fri Jun 21 2024 Ceilings are improving, but lower ones exist with the line of showers/storms tracking into the Wisconsin River Valley late this morning. May see additional development this early afternoon across southwest WI as an outflow boundary makes its way east. MSN and JVL will likely see some showers and storms from this activity. Otherwise, expect light and variable winds as a warm front lifts north this afternoon. Additional shower and storm development expected this afternoon with heavy rainfall reducing flight conditions, especially for areas along and west off I-39/90. Also cannot rule out a stronger storm or two this afternoon and evening with gusty winds being the main concern. Wagner && .MARINE... Issued 447 AM CDT Fri Jun 21 2024 Expect light northerly winds over Lake Michigan today as high pressure weakens over Lake Superior. Light northeast winds this evening will then shift to modest southerly over the southern half of the lake as a warm front moves northward. The warm front and southerly winds will then extend into the northern portion of the lake for Saturday followed by low pressure around 29.7 inches tracking east across central Lake Michigan early Saturday evening. A cold front will quickly follow with modest northwest winds over the entire lake for Sunday. Rounds of thunderstorms are expected across the lake at times from this afternoon into Saturday night. Areas of fog, possibly dense, will be possible over the far southern portion of the lake today then possible over much of the lake late tonight into Saturday evening. Gehring && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ056-WIZ057-WIZ058-WIZ059- WIZ063-WIZ064-WIZ065...2 PM Friday to 7 PM Saturday. 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