NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 052357
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
657 PM CDT Fri Jun 5 2026

.KEY MESSAGES...

- Increasing humidity and thunderstorm chances tonight with a 1
  out of 5 (Marginal) risk for severe storms. Hail, gusty
  winds, and lightning will be the main hazards.

- A very humid airmass will return Monday and Monday night ahead
  of approaching low pressure with widespread showers and
  scattered thunderstorms forecast.

- Hot and humid conditions expected mid to end of next week with
  some potential for Heat Advisory conditions late next week.

&&

.UPDATE...
Issued 658 PM CDT Fri Jun 5 2026

Increasing MUCAPE (~1500 J/kg) over southern Wisconsin this
evening will allow for maintenance of a broken line of
thunderstorms currently sinking southward through central
Wisconsin. Expecting the primary hazards with these storms to be
hail and gusty winds. An isolated cell may become strong enough
to produce hail up to 1 inch in diameter, primarily in
southwestern Wisconsin. Storms will continue southward through
early Saturday morning.

MH

&&

.SHORT TERM...
Issued 157 PM CDT Fri Jun 5 2026

This afternoon through Monday night:

Heavy rainfall has fallen today over sw WI where a Flood
Advisory is in effect for Lafayette County. A west to east swath
of 3-5 inches of rain has fallen. There is some road flooding
in the Cuba City area. Otherwise 1-2 inches has fallen south of
I-94. This efficient rainfall is a result of moist adiabatic
lapse rates within a high PWAT atmosphere of 1.7 inches. The showers
are finally decreasing over sw WI, but will continue to increase
over far se WI into the middle afternoon as a shortwave trough
slowly moves from ne IL to over Lake MI. Brief heavy rainfall
rates are expected.

For this evening into the overnight, another shortwave trough
currently over se MN and north central IA will move to central
WI for early evening, while a stronger shortwave trough over
ern ND moves into ne WI after midnight. At the sfc, a broad area
of low pressure will move ewd from MN across the nrn half of WI
and the Lake Superior region this evening with just a weak wind
shift to wly over srn WI. MUCAPE of 1000-1500 J/KG will be in
place tnt with one or two clusters of thunderstorms moving
across the nrn half of WI. However, the srn periphery of those
storms could drift into central WI and/or isolated to scattered
storm development is expected over much of srn WI as well. The
CAPE values and mdt effective shear does yield a Marginal Risk
of severe storms with large hail and damaging winds the main
concern. The chances for showers and storms will then greatly
diminish around or just after sunrise with 500 mb height rises
expected for the remainder of the day, while sfc ridging builds
from Ontario south across Lake MI into Sat nt.

The high will begin to already move ewd on Sunday as a broad
upper trough over the central and srn Great Plains slowly lifts
toward the Upper MS River Valley or srn Great Lakes for Mon-Mon
nt. Abundant moisture with PWATs approaching 2 inches will
accompany the upper trough. Widespread showers and scattered
storms are currently forecast for Mon-Mon nt, but could start as
early as late Sun afternoon or night over sw WI. If the upper
trough and moisture plume can directly lift into srn WI, concerns
for flooding will increase.

Gehring

&&

.LONG TERM...
Issued 157 PM CDT Fri Jun 5 2026

Tuesday through Friday:

Latest model guidance is showing that southern Wisconsin will
remain on the northwest side of upper ridging Tuesday through the
end of next week. This is expected to result in a persistent
stretch of warm and humid conditions through this period.
Precipitable water values are forecast to be 1.5" to 2.0" per 12Z
deterministic models, with dewpoints anywhere from 65 to 75.
Above normal high temps in the mid to upper 80s may crack the low
90s at times, with 925 mb temps upwards of 25C expected. Overall
though, ECMWF and GFS ensemble probabilities of hitting 90
degrees are only in the 10-25 percent range, so confidence isn't
high yet in getting quite that warm.

Given the warm and humid conditions mid to late week next week,
plenty of instability is expected each day. Since southern
Wisconsin will be on the northwest side of the upper ridge, the
door will be open for a couple shortwaves to move through during
this period, bringing a chance for showers and storms at times.
Additionally, the forecast temps and dewpoints suggest the
potential for the heat index to crack 100 degrees at times. The
timing of the higher precip chances and hottest temps are still in
question though, given uncertainty in the timing of the individual
shortwaves, as this forecast period is still a few days out.

DDV

&&

.AVIATION...
Issued 658 PM CDT Fri Jun 5 2026

Ceilings between 2500 and 3500 ft this evening within some
isolated showers. A broken line of thunderstorms will progress
southward late tonight into early Saturday morning, bringing
ceilings around 2500 ft and the threat of lightning. An isolated
strong storm may produce damaging wind and hail generally less
than 1 inch in diameter. Storm chances diminish along and south
of the I-94 corridor, but potential remains for storms to
maintain intensity and progress all the way through the WI/IL
border.

Southwesterly winds through much of tonight will shift to become
northwesterly as a cold front works its way through Saturday
morning. Winds will become light and variable Saturday afternoon
into Saturday evening, with an easterly lake breeze expected
along Lake Michigan terminals.

MH

&&

.MARINE...
Issued 157 PM CDT Fri Jun 5 2026

Broad low pressure of 29.6 inches will slowly move across the
northern Great Lakes this afternoon and evening. Its weak and
decaying cold front will then follow for Saturday afternoon. Thus
modest south winds today will shift west to southwest tonight and
Saturday morning, followed by light and variable winds Saturday
afternoon. During this time, areas of dense fog will be possible
due to humid air flowing over the cold lake. Light northeast
winds will then prevail Saturday night and Sunday as high
pressure around 30.0 inches builds across the region. Looking
ahead, the start of next week will bring an additional low
pressure system to develop over the Great Plains and approach
Lake Michigan with modest southeasterly winds expected.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory...LMZ643-LMZ644 until 10 PM Friday.

     Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ868 until 1 PM Saturday.

&&

$$

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