textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Mostly dry tonight into tomorrow, save for a few potential showers along the lake breeze this afternoon.

- Dense fog Advisory in effect mainly for counties close to Lake Michigan but extension further west may be needed. Marine Dense Fog continues through Friday.

- A Flood Watch is out for all of southern Wisconsin from 1pm Friday to 7am Saturday for more heavy rain Friday afternoon and evening.

- Another round of heavy rainfall, flooding, and severe thunderstorms is expected Friday afternoon into Friday night. An Enhanced Risk (3 out of 5) for severe weather exists over the western half of the CWA.

SHORT TERM

Issued 1115 PM CDT Thu Apr 16 2026

Today through Saturday night:

Dense Fog Advisory has been expanded for areas further inland as dense fog continues to push west in off the lake causing the expectation that with model guidance we should see dense fog overspread at least eastern portions of the CWA but expansion may be needed further west. Low clouds and fog concerns may extend as far west as Madison tonight and likely clear by mid morning. This will be the main concern for the tonight period as conditions otherwise remain quiet and dry with weak high pressure over the east with some easterly flow off the lake guiding the low clouds and fog inland. Even after skies clear Friday morning easterly component to the winds off the lake will cause a lake breeze for at least areas closest to the lake perhaps more inland than expected as well.

Then attention turns toward the severe storm potential during the day and evening Friday. Still plenty of uncertainty on the timing of storm initiation and who will get hit when but storms appear likely to impact all of southern WI at some point with storms into western WI as early as noon. However, more widespread chances are to be expected by the later afternoon and early evening with storms tracking across southern WI into the evening. Initiation is possible with the pre-frontal wave aloft and although it appears weak in models several CAMs show an earlier initiation of storms toward midday. The better and more widespread initiation potential appears likely to come along the front from a low swinging NNE into northern WI through the day. Instability across western parts of southern WI will climb to around 2000-3000J/kg of MUCAPE by around early to mid afternoon, though the instability simply is not as good further east . In addition, ~300m2/s2 of 03km SRH and 150 m2/s2 of 0-1km SRH as a result of the LLJ sliding through will add significant low level turning in the low to midlevels. While a cap may be in place in the morning the combination of low level warming, increased moisture and strong forcing will trigger storms, the only uncertainty is with any pre frontal storms in that respect. Turning to the hodograph and we get a much clearer picture of our low level environment in its entirety. Model soundings are suggestive of massive low level turning with plenty of speed shear aloft with very high STP values of 2-4 across our west and potentially higher in mesoscale environments.

There are a few things with this event however, that will greatly impact exactly what we could see in our CWA Friday.

First, where/when will initiation begin along the front? If this occurs earlier and further west the initially discreet storms will eventually become linear by the time storms reach or west bring primarily a QLCS wind/embedded tornado risk. If initiation is later and further east then we likely see some of the discreet supercells and all hazards would be possible with much stronger tornadoes possible. Even then storm mode would still be expected to be linear by the time storms reach the eastern half of the CWA.

Second, do we see a few pre-frontal storms? While this is the most uncertain aspect of this event given limited forcing ahead of the front and some capping concerns, but it is most certainly the most dangerous. Isolated supercell convection earlier on and out ahead of the eventual frontal based convection will bring the highest risk for an isolated supercell with an uncontaminated and ripe air mass with plenty of instability and the shear conditions will remain the same. All hazards would be possible with a storm of this type but would also yield much higher potential for a very strong tornado, very large hail (2+ inches) and strong winds within the RFD. Impacts would be more localized but high impacts would be possible. This remains uncertain but the potential is there in some CAMs.

Lastly, how long into the night does the severe risk last? The answer to this is likely through the evening carrying through the entirety of the CWA. However, storms are generally expected to weaken as they push east especially with the afternoon lake breeze potentially being fairly strong and impacting convection further east. This weakening could be faster than expected given the quickly declining instability to the east and the impacts of the lake breeze could cause convection further east to become elevated. But the other issue is it could actually help locally increase severe concerns as it has earlier this week. The storms could simply overpower the lake breeze and the storms could end up using any lake breeze boundary to enhance the low level environment locally increasing shear. This could increase the QLCS tornado threat.

Lots of factors and elements to consider with this event that add to uncertainties but the key is the environment will be ripe for severe weather, especially for the western half of the CWA.

Friday night front will push through and this will usher in a much cooler and drier air mass across southern WI with higher pressure pushing in. Despite the upper low expected to be overhead Saturday the upper levels will be too dry likely allowing for clear skies though chiller temperatures with highs in the mid to upper 40s and breezy west to northwest winds.

Kuroski

LONG TERM

Issued 1115 PM CDT Thu Apr 16 2026

Sunday through Thursday:

Into next week looks likely to bring a period early on of drier conditons with higher pressure remaining in large part overhead with weak ridging aloft. Monday night into Tuesday will bring the next best chance for precip though there are question in regard to midlevel moisture but the upper level dynamic and surface front pushing through suggest at least a decent chance. There would likely be somewhat of a chance for thunder given some weak instability in models. Into the middle of next week temperatures will remain fairly warm with limited precip chances ahead of Friday.

Kuroski

AVIATION

Issued 1115 PM CDT Thu Apr 16 2026

VLIFR/LIFR CIGS and VSBYS continue to push west. With that we have expanded the Dense Fog Advisory further west through 14z Friday for expected expansion of dense fog across areas further inland tonight. Model guidance slows the progression of fog further west toward Madison but could reach as far as MSN for a period overnight. As we break into daylight Friday morning expect fairly rapid dissipation of the fog and low CIGS by mid morning.

Then attention turns toward the severe storm potential during the day and evening Friday. Still plenty of uncertainty on the timing of storm initiation and who will get hit when but storms appear likely to impact all of southern WI at some point with storms into western WI as early as noon. However, more widespread chances are to be expected by the later afternoon and early evening with storms tracking across southern WI into the evening. Storms are generally expected to weaken as they push east especially with the afternoon lake breeze potentially being fairly strong and impacting convection further east. Storms are generally expected to push out of southern WI by the late evening hours. Some VSBY and CIGS concerns will come with the storms as well though they would be associated directly with storms.

Kuroski

MARINE

Issued 1115 PM CDT Thu Apr 16 2026

Winds becoming light and variable tonight for a time as a weak surface ridge moves over the lake. Dense fog will continue over the lake through this time and perhaps until the front comes through Friday night. Winds then come around to southerly tomorrow morning as a surface low of 29.5 inches approaches from the central plains. This surface low will quickly move from Omaha to Duluth from the morning into the afternoon. Winds will become gusty and southeasterly Friday night, and strong to severe storms will move east over the lake as a cold front sweeps through the area. Winds then become northwesterly behind the cold front Saturday morning. Breezy northwesterly winds then continue Saturday through Sunday as the low then races northeast toward Hudson Bay. Winds ease Monday morning as high pressure move southeast over the upper Great Lakes.

Small Craft Advisory is now in effect Friday afternoon until Saturday evening for breezy winds and high waves in the nearshore. Southerly winds ahead of the front and then gusty WNW winds behind the front.

Kuroski

MKX WATCHES/WARNINGS/ADVISORIES

WI...Dense Fog Advisory...WIZ052-WIZ059-WIZ060-WIZ065-WIZ066-WIZ070- WIZ071-WIZ072 until 9 AM Friday.

Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058- WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067- WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...1 PM Friday to 7 AM Saturday.

LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563- LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 until 7 PM Friday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...1 PM Friday to 10 PM Saturday.