NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 171536
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1036 AM CDT Sun May 17 2026

.KEY MESSAGES...

- Scattered thunderstorms this morning into the afternoon.
  Severe storms are not anticipated, but possibly small hail and
  gusty winds with the stronger storms.

- More rounds of showers and storms late tonight into Mon then
  again late Mon night into Tue, but much uncertainty for
  severe storms given the morning timing of potential MCSs.

- Cool and drier weather then returns for Wed-Thu.


&&

.UPDATE...
Issued 1020 AM CDT Sun May 17 2026

Now that we are beginning to see the hand that is being dealt,
lets break it down:

Remnant decaying complex moving across southern WI this morning
bringing showers through late morning and departing early
afternoon. While this MCV is moving over a highly stable
environment with the onshore flow off of Lake Michigan, have
seen parts of this system tap into the elevated instability
(MUCAPE ~500-1000 J/kg) and perk up enough to produce a few
thunderstorms. As the MCV pushes eastward through the early
afternoon, may see additional redevelopment with some daytime
heating and beginning to see signs of this back in northeastern
IA/southwestern WI. However, still uncertain on if this will
become more widespread or if the stable marine layer will win
out as it departs. If things are able to recover enough and tap
into the elevated environment, then a few isolated strong storms
cannot be ruled out now through the early afternoon with some
hail possible with the departing MCV, which looks to push east
after noon between 18z-20z. While severe potential remains on
the lower side at the moment, will need to monitor as MCVs are
notorious for creating localized environments that can support
healthier/stronger storms right along the feature.

The next area to watch is behind the departing MCV. While the
onshore flow and lingering clouds will keep parts of southern WI,
mainly north of I-94 in a more cool/stable environment, there is a
warm front stalled just south into northern IL. Initial runs of the
12z models are hinting that we see this warm front lift back
northward this afternoon bringing warm/moist airmass back into
southern WI, generally south of I-94. Accompanying the surface
front progression will be increasing instability (SBCAPE of
+1500 J/kg) along with lift from low-level WAA as well as a
nose of 30-40 kt LLJ. So some of the ingredients for stronger
storms may present itself later this afternoon along the warm
front, but the questions remains how the morning round of
showers, clouds, as well as easterly onshore flow off of Lake
Michigan limit the northward advancement of the warm front or
if the environment is worked over too much. So for this round
of activity will need to see how things lie in the next few
hours, but leaning toward the cooler air limiting the threat.

While uncertainty on environment recovery remains in play,
especially for southeastern WI, it does have a better chance
across southwestern WI where storms and clouds depart sooner.
So while we need to monitor for potential development later
this afternoon and evening, will also need to keep an eye on how
things play out upstream across western IA into the Plains. If
we do not see storms develop along the lifting warm front in
the afternoon/evening, the environment will be more supportive
of overnight storms that develop across the Plains and push
into the area overnight into Monday morning. Instability with
SBCAPE of +1000 J/kg and meager (30-35 kt) deep layer (0-6km)
shear paired with low-level forcing may be enough to maintain
the storms strength into our western portions of the CWA. The
12z CAMs continue to show a line of storms developing upstream
in IA and pushes east overnight. This would bring more of wind
threat to southwestern WI with the line. However there are two
camps with the line. One camp with the 12z HRRR, NSSL, and RRFS
having the line making to southwestern WI and gusting out as it
pushes eastward, likely favoring the warmer solutions winning
out while the other camp 12z NAM Nest and ARW weakening the line
and/or have it dive further south of the WI/IL border favoring
the cooler solutions. At this time temps are under performing
and hedging the forecast more toward the cooler solutions, but
it also will not take much for the warmer solutions to pan out
as well. Either way, the line of showers and storms is expected
to move through southern overnight, generally after midnight
departing around daybreak Monday with a weakening trend to the
east.

Regardless, stay weather aware today as there remains multiple
windows for storms now through tonight with potential for strong
to severe storms capable of hail and gusty winds as well.

Wagner

&&

.SHORT TERM...
Issued 1223 AM CDT Sat May 16 2026

Tonight through Tuesday night:

The dry cold front is currently accelerating down Lake MI and
will arrive in the Sheboygan area around 1 AM CDT and MKE around
4 AM CDT. Farther to the southwest, a west to east line of slow
moving thunderstorms extends from ne IA into sw WI, probably
triggered by elevated warm, moist advection. A sswly low level
jet of 35-40 kt is expected to develop over ern IA and nose into
far srn WI toward 10Z so expect scattered storms to develop
over the area. MUCAPE of 1000-1500 J/KG near the IL border will
slowly drift nwd during the overnight, but lapse rates will
weaken resulting in MUCAPE falling below 500 J/KG. Still
expecting small hail within the stronger storms tnt.

Otherwise, more widespread showers and storms are expected from
Sun AM into the early to mid afternoon when 850-700 mb warm,
moist advection and a MCV moves through the region. The MCV will
develop from the severe convection over srn IA and nrn MO tnt and
lift newd into srn WI after 12Z. The remnants of the showers
and storms from NE to srn IA and nrn MO may accompany the MCV or
new development will occur given the aforementioned warm, moist
advection. The mid level lapse rates will drop to 5.5-6.0 C/KM
during this time so elevated CAPE will remain marginal with
perhaps small hail with the stronger storms. The sfc warm front
will not reach a line from Madison to Kenosha until late
afternoon but temps will quickly warm to near 80F once it
passes. High temps toward central WI should only reach into the
60s with 50 and 60s at the Lake MI shoreline.

A wave of low pressure will then track from ern NE to nw WI by
12Z Mon, while a decaying MCS from srn MN and IA may be
arriving after 09Z Mon over south central WI. The wave of low
pressure will weaken as it tracks newd across Lake Superior into
Ontario during the day, but will aid in continued warm, moist
advection over srn WI. A MCV may also be present within the
decaying MCS, and will forecast 60-70 percent chances for
showers and sct storms. The severe storm potential is very
uncertain given the morning arrival of showers and storms and
there may be a lack of forcing later in the afternoon.

Another wave of low pressure will develop from the central
Great Plains to nrn WI by 12Z Tue, while the main shortwave
trough tracks from the central Rockies to nw WI. The actual
trailing cold front will likely not pass until Tue, but there is
some confidence in another round of showers and storms for Mon
nt-Tue AM given srn WI remains downstream of areas of new
convective initiation and possible MCSs. The potential for
severe storms is very uncertain given the morning timing.

Gehring

&&

.LONG TERM...
Issued 1223 AM CDT Sat May 16 2026

Wednesday through Saturday:

High pressure and a cooler air mass will follow for Wed-Thu
with lgt sly winds and warm advection returning late Thu into
Sat as the high moves ewd and a shortwave trough approaches
from the west. Thus high temps in the 60s for Wed-Thu will
return to the 70s well inland from Lake MI for Fri, then 70s
over all of srn WI on Sat. A slight chance for showers is
forecast Fri nt-Sat.

Gehring

&&

.AVIATION...
Issued 618 AM CDT Sun May 17 2026

A cluster of thunderstorms is expected to move in from the
southwest this morning, with scattered storms then lingering
into the afternoon. As the storms move in, ceilings are expected
to lower to low VFR to MVFR, with other potential drops in
flight category due to vis restriction. Winds will be breezy,
out of the east to southeast.

There should be a lull in activity late in the day, with
ceilings giving way to SCT to FEW skycon tonight. More
thunderstorms may move in from the west around daybreak on
Monday.

CMiller

&&

.MARINE...
Issued 1223 AM CDT Sat May 16 2026

A cold front over central Lake Michigan early this morning
will track to far southern Lake Michigan by daybreak. A wind
shift to the northeast is expected along with brief gusty winds.
The front will then gradually return north as a warm front
mainly tonight, with winds veering southerly and becoming
gusty. Areas of fog may form later today and evening as the
front moves northward. Breezy south winds will then continue
into Tuesday followed by a wind shift to the northwest late
Tuesday afternoon and evening with the passage of a cold front.
High pressure and light and variable winds will then take hold
from late Wednesday into Thursday. A Small Craft Advisory may be
needed from Sheboygan to Winthrop Harbor for Mon-Tue due to
persistent and gusty south winds and high waves.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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