Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
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889 FXUS63 KMKX 241738 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1238 PM CDT Fri May 24 2024 .KEY MESSAGES... - Another round of strong to severe thunderstorms will be possible this afternoon and early evening, but the extent of it should be limited by persistent cloud cover and ongoing precipitation. - Keeping an eye on another round of thunderstorms on Sunday, but the more favorable environment remains just south of southern WI at this time. && .UPDATE... Issued 1237 PM CDT Fri May 24 2024 Persistent low to mid level warm, moist advection is producing showers and storms over ern IA into sw WI. This is expected to continue until the cold frontal passage early this evening. Initially these storms will remain elevated due to large MLCIN in the wake of the ongoing showers and storms, but a sly LLJ of 30-40 kts will maintain warm advection and moisture transport with MLCAPE possibly recovering to 1000-1500 J/KG. The MLCIN may reduce to 25-50 J/KG by late afternoon and early evening so sfc based convection will be possible. Thus a severe threat remains given effective shear of 30-40 kts and effective SRH of 150-200 m2/s2. All hazards will be possible but the extent of severe should be limited by the aforementioned CIN and somewhat poor low level lapse rates. Gehring && .SHORT TERM... Issued 354 AM CDT Fri May 24 2024 Today through Saturday: Another active pattern is in store for southern WI today as a mid- level trough and accompanying surface low pivot northeastward across the Upper Midwest. This is looking to bring multiple rounds of thunderstorms and each bringing a potential for stronger to severe weather. The first round will be this morning as an ongoing line of severe thunderstorms currently making its way across the Missouri River Valley along the NE/IA border is progged to lift into southern WI. The big question with this activity is will it maintain its strength as it tracks eastward early this morning. Current it anchored to the instability axis aligning with the effective shear zone and LLJ. While SPC mesoanalysis shows CIN associated with the upstream SBCAPE >1000 J/kg , these showers seems to be overcoming the CAP at this time. Given the trends along with some developing convection out ahead of it along the effective warm frontal boundary, thinking there is a pretty good chance we will see this line make it into our neck of the woods later this morning as the instability axis lifts northeastward along with the LLJ persisting. Most of the 00z and later CAMs indicate seeing the line make it up here between 12z-14z for our western CWA, but handle this MCS evolution differently. While the the 00z-04z runs of the HRRR seem to be the more aggressive solutions with this line maintaining it strength as it traversing into southwestern WI. Given the latest trends, is not looking unplausible as long as it does outpace the instability. However, most CAMs including the NSSL-WRF, ARW, and NAM- Nest, weakening the line, especially as the deep layer shear seems to weaken a bit through the morning. The latest 06z seems to be jumping onboard more to this scenario as well. Nevertheless will need to monitor trends as it may have a narrow window as it pushes into the area where it may be strong-severe bringing gusty winds and maybe some hail and with it riding the warm frontal boundary, cannot rule out seeing an embedded QLCS tornado or two with this round, especially with 00z HREF progged 0-1km SRH around 100-150 m2/s2. The better potential for this round of strong-severe storms will be mainly south and west of Madison as the line is progged to weakens as it pushes east. After the morning round of storms, there looks to be a lull for a couple of hours. Then thunderstorm redevelops and activity picks back up as the upper-level trough swings through as the cold front slides across the area. Given the lull and the warm front progged to lift at least into the east-central WI, the environment looks to recovery enough for the next round of development where MUCAPE creeps to around 1000-1500 J/kg and 0-3km SRH exceeds 200 m2/s2. Given the upper-level dynamics, forcing, and mesoscale setup, all severe hazards will be possible with this second round as it develops just upstream or overhead and congeals into a line as it tracks eastward. However, there continues to be some uncertainties with the afternoon/evening round, one of the main point being how does the first round impact the environment and will there be enough recovery between the morning and afternoon/evening round. Another concern is timing as some models like the HRRR are faster in the progression of this storm activity with the other CAMs are a bit slower. Also there are even a solution or two such as the 00z ARW where the afternoon round does not develop likely a result of the lack of recovery behind the morning round and/or the warm front stalling further south. While these are the minority of solutions, there is still a low end potential to see this scenario play out. Otherwise, will lean more on the majority of the hi-res model guidances and bank on afternoon redevelopment with another round of strong to severe thunderstorms mainly after 21z through 03z before the cold front slides through. Once the cold front pushes through, expect high pressure to build in behind and dry/cool things off for Saturday. Wagner && .LONG TERM... Issued 354 AM CDT Fri May 24 2024 Saturday night through Thursday: Saturday night looks fairly quiet as a weak surface high gradually pushes off to the east as a fairly strong low pushes in from the southwest. Sunday morning we will start to see this system push in which will be associated with a fairly strong shortwave aloft. This system will also be heavily influenced by 40-60kt LLJ sliding through the CWA during the day. The severe potential Sunday afternoon exists primarily due to the LLJ and the strong 0-3km helicity and deep layer shear associated with it. While some storms could be expected into the early afternoon the environment may be heavily influenced based on how far north the warm front gets in addition to just how much instability we can muster up, especially when clouds would likely figure into this discussion with ongoing precip/storms from the morning. Several models suggest that much of the activity could really begin too far east to impact the CWA but if there is any chance it seems mostly restricted to southeast parts of the CWA. On the flip side if things are a bit slower in terms of progression it will open up a window for strong to severe storms with all- hazards possible. The deepening surface low will gradually push northwest into the northern Great Lakes region and into Ontario but one thing to point out Sunday night through much of Monday is that some wrap- around precip will be possible (30-40%) due to some shortwave energy lingering in the region along with some moisture. In addition slight effects from the TROWAL may play a role as well. It seems tough to gauge the likelihood of precip given the potential being largely driven by the shortwave energy (placement) in addition to moisture associated with the shortwave energy. Tuesday will also feature continued chances (20-30%) for showers, though weak, due largely to the upper low digging through the region. Wh and will depend on the morning round. If environment recovers between rounds, then could see the potential for near severe hail and gusty winds and even a brief, isolated tornado can`t be ruled out.ile there remains lots of uncertainty with this upper closed low and its progression from central Canada into the western Great Lakes region the main questions will be the moisture associated with it as it appears questionable, which is the main reason for just chances as the forcing will not be the issue. By midweek it appears for at least a short period we will finally return to drier conditions with higher pressure sliding in ahead of ridging aloft Kuroski && .AVIATION... Issued 1237 PM CDT Fri May 24 2024 Rounds of showers and storms will continue this afternoon and evening. Areas of MVFR Cigs and Vsbys may briefly occur in the wake of any of the stronger storms. Areas of MVFR Cigs are also expected for a brief time along and after the passage of the cold front this evening. Skies will then clear during the overnight hours with VFR conditions into Wed. Gehring && .MARINE... Issued 354 AM CDT Fri May 24 2024 High pressure continues to push into the eastern Great Lakes early this morning. Meanwhile light and variable winds early this morning will turn east to southeasterly as warm front lifts northward through the afternoon as a deepening low pressure lifts into the Upper Midwest this evening. This will then drag a cold front across Lake MI overnight tonight turning winds more westerly int Saturday. Also accompanying these frontal boundaries will be rounds of thunderstorms today, but ending later this evening. High pressure will then move across Lake Michigan for Saturday afternoon and evening before another low pressure lifts across the region Sunday. Next week is likely to start off with northwesterly winds as the low lifts out of the Upper Great Lakes region. Wagner && .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