textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Round of isolated to scattered showers and storms possible later this evening/overnight with an isolated strong to severe storm or two possible.

- Additional shower/storm chances from decaying complex tracking across southern WI Sunday morning. Influence from morning showers may limit development later in the day/overnight, but the better chances will for areas west of I-39 Sunday night.

- Another conditional setup for showers and storms later Monday into Tuesday, with better strong to severe potential.

- Warm through the start of the week with cooler temps by the lake, especially Sunday. Then a dry and cooler stretch through midweek.

SHORT TERM

Issued 232 PM CDT Sat May 16 2026

Tonight through Sunday night:

The front has slid south of the WI/IL border and brought a much drier airmass to southern WI this afternoon with dewpoints falling into the 40s-50s. Latest obs show the front with those 60s dewpoints and southerly winds just south in northern IL. However, satellite is showing a cu develop along it likely aided by what seems to be a gravity wave propagating northward from the convection in central IL, but only looks to be enough to spur the cu field as it already seems to decrease in coverage as quickly as it has appeared. Will need to keep an eye on the potential for another gravity wave showing hints just outside the central IL convection clouds shield later this evening as it may be enough to tap into the 1000 SBCAPE and overcome the cap to produce a few pop up storms as the HRRR has been suggesting. However, the HRRR has been the more aggressive solution for convection development his evening while the other CAMs are not as keen on convective development more likely due to the drier airmass settling into WI this afternoon.

Do expect this frontal boundary to gradually lift back northward into southern WI through the evening and overnight as a low lifts from the Plains into the lower Missouri River Valley. Pair with the low-level WAA along with some meager deep layer shear (around 40 kt) could be enough for isolated to scattered storms to develop along and just north of the warm front boundary with a whack-a-mole for a strong to severe storm or two capable of producing hail approaching severe limits and sporadic splats of winds with any collapsing storm. Overall window for this activity looks to be between as early as 00z-03z with better chances toward 06z, but instability and shear is progged to diminish through 09z, thus the storm potential does as well.

Then looking at another round of showers and storms into Thursday morning associated with any upstream convection the develops across the more favorable environment back toward the low in the Plains. CAMs continue to hint that the decaying complex will push across southern WI Sunday morning. Depending on the timing of this feature will influence additional thunderstorm chances for Sunday. later arrival may hinder the environment from recovering enough for development later in the day, while an early passage may condition the area south of that lifting warm front for convection later in the day. However, easterly flow off of Lake Michigan will also contribute to the convection potential Sunday, especially for areas further east as the marine layer may keep things more stable. Thus the better potential continues to remain for the western portions of the area for additional storm development. While a very conditional set up for southern WI tomorrow with the better upper-level setup and dynamics further west, still looks to be a window later in the evening and overnight, especially for areas along and west of I-39 depending on the morning activity.

Otherwise temps will be cooler for central WI and along the lakeshore with lows in the upper 40s and lower 50s while milder toward the WI/IL border and lows in the mid to upper 50s to around 60F tonight. Will see another warm day for inland southern WI on Sunday behind the morning clouds and showers with highs in the 70s and even crack 80F again, unless morning activity is slower to move out. Meanwhile southeast-east winds off of Lake Michigan is expected to keep it cooler for areas along and east of the Kettle Moraine to the lakeshore with some uncertainty on how far inland this will lake influenced temps will actually make it.

Wagner

LONG TERM

Issued 232 PM CDT Sat May 16 2026

Monday through Saturday:

Continue to monitor Monday for severe potential as SPC has the area outlooked with a Slight risk (2 out of 5). However, it continues to remain a conditional set up for severe for southern WI as uncertainty remains, especially in the alignment of the forcing/dynamics as well as timing with latest guidance suggesting a more of a later/overnight Monday timeframe. Nevertheless, will need see how things evolve over the next day or two because despite the uncertainties an upper-level trough across the Pacific Northwest Sunday is progged to dig into the Plains with a mid-level shortwave trough traversing up across the Upper Midwest for Monday. An interesting low-level pattern takes shape with a surface low tracking from MN across Lake Superior early in the day Monday with a cold front draped to south followed by another surface low pressure progged to develop in the Plains and lift across IA into WI later Monday into Tuesday. A 40-50 kt LLJ does look to nose in with the second low paired with the higher instability pushing into the region. While EPS and GEFS ensembles generally agree on this track, the exact timing and any wobble in the track along with where the associated effective warm front, moisture advection, and instability axis set up will be the main driver of any severe development across our neck of the woods. Will continue to monitor, but models seem to be trending more toward an overnight severe setup for at least portions of southern WI and may linger into Tuesday morning.

Also looking at the frontal passage to be delayed behind the severe and work its way through southern WI during the day Tuesday before sliding southeastward later in the afternoon. Behind the front expect not as warm conditions to filter in with high pressure building across the area along with a drier airmass through midweek. Then the pattern gradually turns a bit more active for the end of the week as model cluster favor a shortwave trough traversing the central CONUS during this time, which will bring warmer temps along with some additional low end precip chances into next weekend.

Wagner

AVIATION

Issued 232 PM CDT Sat May 16 2026

Light westerly winds and VFR conditions continue through the evening. Then looking at mid-high clouds to spread back in tonight with isolated to scattered shower and thunderstorm chances between 00z-09z tonight where cannot rule out a strong storm or storm or two capable of producing hail and gusty bursts of winds. Then upstream storms in the Plains look to gradually weaken and push across southern WI Sunday morning. With any showers or storm activity, could see periods of lower ceilings and visibility. Some lower ceilings around MVFR levels may lingering in between rounds of showers through Sunday morning, but expecting VFR conditions to return later Sunday with east- southeast winds fro terminals near Lake Michigan while more southerly winds for inland southern WI terminals. Additional rounds of showers and storms will be possible later Sunday evening/night especially for terminals along and west of I-39 corridor.

Wagner

MARINE

Issued 232 PM CDT Sat May 16 2026

Southerly winds persist as the front stalled south of Lake Michigan this afternoon is progged to lift back northward overnight as low pressure develops over the Plains and gradually weakens as it lifts into the Upper Mississippi River Valley Sunday into Monday. Then southerly winds increase as another low pressure lifts across IA/WI into Lake Superior later Monday into Tuesday. This low will drag a cold front across the Lake during the day Tuesday turning winds more west- northwesterly overnight into Wednesday. Lighter winds expected Wednesday through the end of the week as high pressure builds across the region.

Expect periods of small craft conditions to develop across southern WI nearshore waters with the stronger southerly winds later Sunday through the start of the week.

Wagner

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.