NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 081112 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
612 AM CDT Mon Jun 8 2026

.KEY MESSAGES...

- A very humid airmass will build into the region today ahead of
  approaching low pressure, with widespread showers and
  scattered thunderstorms forecast this afternoon into tonight.

- Showers and storms today will be slow moving and capable of
  heavy rainfall. Localized flooding is possible. General
  rainfall totals will be between 0.5 and 1.5 inches, but
  locally higher amounts will be possible. A brief, isolated,
  spin-up tornado also can't be ruled out.

- Hot and humid conditions expected mid to late week, with some
  potential for Heat Advisory conditions on Wednesday.

- Severe thunderstorms are possible Wednesday. There is a lower
  risk for severe storms on Thursday.

&&

.UPDATE...
Issued 612 AM CDT Mon Jun 8 2026

Scattered showers and isolated thunderstorms developed in
northern IL and expanded into southern WI shortly after 1 AM.
They developed along an area of vorticity advection and were
also aided by the low level jet. They were widely scattered for
a while, but not are in a NW to SE oriented band. Precip rates
are in the 2 to 3 inch per hour range, but the band of rain is
steadily tracking northward. Southeast Rock county picked up
around an inch already (radar estimated).

The main area of precipitation that we're keeping an eye on is
currently in eastern IA because it's associated with a mesoscale
convective vortex (MCV) and the southern edge of it would be the
typical spot for deeper convection, heavier rain rates, and a
brief, low-topped supercell that could produce a tornado. The
center of this MCV is now looking like it will track just to the
WEST of the MKX forecast area.

There is currently a more intense band of rain extending from
the MCV into northwest IL. This band will lift northward to the
WI border by 8 AM and bring some heavier rainfall rates, but
probably to areas not hit hard within the past 6 hours. We will
be watching for repeated rounds of these more intense rainfall
rates all day to monitor for the risk of areal flooding or flash
flooding.

Steady southeast winds will prevail today and lead to high waves
at beaches north of Wind Point today into this evening. A Beach
Hazards Statement for a high swim risk is in effect.

Cronce

&&

.SHORT TERM...
Issued 100 AM CDT Mon Jun 8 2026

Today and Tonight:

Both model guidance and observed Satellite / Radar trends
suggest that the coverage of any predawn showers / storms should
be lower than prior expectations, widely scattered and weak at
best. The MCV currently over northern Missouri will continue to
track northward this morning, heading for northeast IA (or
perhaps directly overhead) this afternoon. As it approaches, we
expect to see the coverage and intensity of storms gradually
ramp up in a SW to NE manner, peaking late this afternoon into
this evening before tapering down late tonight. With PWAT of
1.7-2.1 inches and WCL depths over 10,000 ft, all showers +
storms will be very efficient rain makers. With potential for
training and clustering convection, this would mean potential
for localized heavy rainfall and flash flooding. The exact
track of the MCV is not fully certain, but wherever it sets up,
storms to the south and east of it this afternoon will
experience locally backed surface winds and higher helicity,
which coupled with the low LCL heights and building 3CAPE could
support a brief spin-up tornado. That said, the primary hazards
for today are localized heavy rainfall and lightning.

Sheppard

&&

.LONG TERM...
Issued 100 AM CDT Mon Jun 8 2026

Tuesday through Monday:

Synopsis:
A pronounced upper ridge axis over the eastern Great Lakes and
negatively tilted trough axis over the northern Rockies will both
slowly progress eastward through the rest of the work week before
breaking down into a predominantly zonal pattern for this weekend.
We expect the heat and humidity to peak midweek (Wednesday)
followed by a slow cool down towards seasonal norms by early next
week. Periodic chances for showers and thunderstorms are forecast
through this period, with a particular emphasis on Wednesday and
Thursday for some more organized / stronger storm potential.

Details:
Predominantly dry weather expected on Tuesday, with Monday's
convective activity exiting east and leaving some subsidence in
it's wake. The fuel (CAPE) for a stray thunderstorm will be
present in the region, particularly further south and west,
though the predominantly subsident motion should keep us dry.
The 18z GFS does resolve a 500mb vorticity maxima and attendant
PVA crossing our region Midday (not quite in phase with peak
diurnal heating), but this remains an outlier. The 00z HRRR
suggests potential for Monday's convection to form an MCV that
lingers long enough for widely scattered shower activity to
persist into Tuesday. That said, the overall consensus is dry
weather, and precip chances have been capped at 15% for now.
Additional 40-60% precip chances are in place late Tuesday
night, mainly on account of a dying storm complex (triggered to
our west) attempting to push into southern WI.

The heat and humidity may approach Advisory levels (heat index
100-104) on Wednesday, though any remnant cloud cover from the
potential overnight convection (or an earlier-than-expected
convective initiation Wed afternoon) could easily hold us just
shy of criteria. Our best guess is (once again) predominantly
dry weather through the daytime hours, with plenty of fuel
(likely 3,000 joules CAPE or more) available for a stray storm
but no substantial mechanisms to trigger one. A potent 500mb
trough digging into Minnesota ought to serve as the focal point
for convective initiation Wednesday afternoon, likely near west-
central WI / southeastern MN. Both the trough and storms would
then track eastward, and depending on how early (in the evening
/ night) it arrives, plenty of instability would be present to
support severe weather. The earlier it arrives, the worse it
could be.

Yet another 500mb trough with strong PVA and shear is expected to
trigger convection on Thursday, with model guidance suggesting
this one will be more or less "overhead". That said, ensemble
guidance substantially lowers the fuel / CAPE for Thursday, likely
on account of Wed evening / night's convective activity sweeping
it out and resetting the warm sector to our southeast. For now,
both Wednesday and Thursday are potential candidates for severe
storm activity in our region. An early arrival of convective
activity Wednesday (or a failure for it to reach southern WI at
all Wednesday night) would leave higher CAPE Thursday.

Such an active weather pattern leaves little in the way of
'predictability' for Friday and beyond, though the general
consensus is a transition to predominantly zonal flow in the jet
overhead, with temperatures trending closer to seasonal norms into
early next week.

Sheppard

&&

.AVIATION...
Issued 612 AM CDT Mon Jun 8 2026

Bands of showers/storms will track northward through southern
and central WI today. Rainfall rates will be efficient (2 to 4
inches per hour), so any slow-moving thunderstorms or repeated
rounds of storms could produce flash flooding. Ceilings will
become progressively lower as the day goes on, falling to MVFR
with pockets of IFR this evening. Showers and thunderstorms will
gradually diminish from west to east late tonight into Tuesday
morning.

Cronce

&&

.MARINE...
Issued 612 AM CDT Mon Jun 8 2026

High pressure over the Lower Great Lakes will continue to shift
eastward today. Light to moderate southeast winds developing
over Lake Michigan will persist through this evening. A Small
Craft Advisory is in effect through late afternoon. Bands of
showers and thunderstorms will lift northward through WI and
Lake Michigan today and tonight.

Winds will become southerly and storms become more isolated
behind the front on Tuesday. A brief period of light and variable
winds may occur Tuesday evening, followed by gusty south winds
into Wednesday as low pressure deepens west of the region.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071 until 7
     PM Monday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645 until 4 PM Monday.

&&

$$

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