NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 161935
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
235 PM CDT Sat May 16 2026

.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.
&&

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, X, and YouTube at:
www.facebook.com/NWSMilwaukee
www.x.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee