NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 152354
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
654 PM CDT Wed Apr 15 2026

.KEY MESSAGES...

- Thunderstorms will move across the area this evening posing a
  risk of hail to the size of quarters, wind gusts to 60mph and
  perhaps a tornado or two. This activity has moved into
  southwestern WI and should exit to the east by 11 PM. Areas
  along the WI/IL border and southeastern WI have the best
  chances to see a severe storm.

- Heavy rainfall this evening into the overnight hours will
  maintain a risk for flash flooding into Thursday morning. A
  Flood Watch remains in effect for all of southern Wisconsin.

- Another round of heavy rainfall, flooding, and severe
  thunderstorms is expected Friday afternoon into early
  Saturday morning.


&&

.UPDATE...
Issued 654 PM CDT Wed Apr 15 2026

A messy mesoscale setup this evening as showers and
thunderstorms continue to expand across the region.

Airmass recovery has been slow, but good enough to slip into
southern WI, mainly along/south of I-94 corridor. Best dewpoints
are along/south of the state line and a few supercells have
developed over the past hour or so. Closely monitoring the
behavior of these storms as they approach and cross the state
line, where one of a few nebulous boundaries reside. The
circulation with the supercell just south of Green county has
maintained its character as it has crossed the state line,
which gives at least some indication that there is a boundary in
far southern WI.

For much of the mid/late afternoon, we have observed scattered
to numerous showers and storms north of the boundary, which has
maintained low 60s dewpoints, but have kept temperatures largely
in the low/mid 60s, with the exception of far southeastern WI
where temperatures have poked into the 70s. A slightly better
thermo environment in far southeastern WI is worth noting as we
could see an uptick in intensity as activity moves to the east.

Unlike the past few days, this set up is a bit more uncertain
and subtle mesoscale changes will be the focus to learn if
storms are slightly elevated or becoming more rooted to the
surface, which will open the door to an increased wind
potential, along with the risk for a tornado or two.

Heading into the overnight hours, we will remain moist and as
the shortwave moves into the region additional areas/bands of
showers and embedded storms will linger.

Gagan

&&

.SHORT TERM...
Issued 335 PM CDT Wed Apr 15 2026

Tonight through Thursday night:

More thunderstorms are possible this evening as return flow is
expected to advect appreciable SBCAPE from 1000 to 1500 J/kg
into southwest WI and up to the WI/IL border. Storms tonight may
be a bit weaker than yesterday given skinnier CAPE profiles, but
low level instability, effective shear around 40 knots, and
some curvature in the hodographs will support another round of
gusty winds and hail. An isolated tornado can't be ruled out
along the WI/IL border given the low level turning in the
hodographs and low level instability, provided a low-topped
supercell forms in the environment this afternoon.

Storms will quickly grow upscale after sunset, leading to more
widespread rain. Training thunderstorms may lead to more flash
flooding tonight given the wealth of rain we've had this week. A
Flood Watch is in effect from 4pm this afternoon to 7am Thursday
for the expected rainfall tonight. A widespread 1 to 2 inches
may fall, with locally higher amounts possible where any
thunderstorms track.

Storms largely move offshore tonight around midnight, with more
scattered rain possible between midnight and 7am. Rain should
then largely taper off Thursday morning, with dry conditions
Thursday afternoon. A weak surface ridge will then move overhead
Thursday night.

CMiller

&&

.LONG TERM...
Issued 335 PM CDT Wed Apr 15 2026

Friday through Wednesday:

A strong cold front is expected to move through Friday afternoon
and evening and is expected to lead to another round of severe
weather. At this time the GFS depicts strong warm ahead of the
front which will allow dew points in the 60s to return
northward. Model soundings depict 40 knots of effective shear
amid moderate instability of 2000 J/kg, with low level turning
in the hodographs. This would support all modes of severe
weather again for the area. At this time the SPC has included
southwest and south central Wisconsin in an enhanced risk for
severe weather.

The cold front will then come crashing through Friday night into
Saturday, and temperatures will dip into upper 40s to low 50s
for the weekend. Saturday is expected to be cool and breezy,
with breaks in the clouds late in the day. Sunday will feature
similar conditions but will be a tad bit sunnier as a high
pressure center moves overhead.

Warmth is then expected to return next week Tuesday as a ridge
builds over the central United States. The middle of next week
then looks active again as a low pressure moves off of the lee
of the Rockies.

CMiller

&&

.AVIATION...
Issued 654 PM CDT Wed Apr 15 2026

Primary concern for this evening is another round of showers and
storms. The severe risk is a bit more uncertain, but high enough
to be concerned with localized damaging winds and hail. There is
a small tornado risk. MVFR to brief IFR visibility is expected
with heavy downpours of rain. Lightning risk will be highest
this evening as storms move west to east and exit over the lake
after 04 UTC. Heading into the overnight hours, showers and a
few storms will persist in a scattered fashion, with visibility
and ceilings lowering through the MVFR category. Prior to
daybreak Thursday will be the best window of opportunity for IFR
ceilings and visibility. Conditions will gradually improved
during the day Thursday, with clearing expected in the mid to
late afternoon.

Gagan

&&

.MARINE...
Issued 251 PM CDT Wed Apr 15 2026

A stationary front will remain parked over the middle third of
the lake this afternoon, slowly sinking south to the southern
end of the lake by noon Thursday. A Marine Dense Fog Advisory
continues until Thursday morning while this front lingers.
Winds will remain southerly south of the front and modestly
breezy, while winds north of the front will remain light and
variable to northerly during this time. The front will then
clear the lake Thursday afternoon and northerly winds will
prevail over whole lake. Winds will become light and variable
briefly Thursday night as a weak ridge passes over the lake,
with winds then becoming southerly and breezy Friday ahead of
low pressure of 29.6 inches approaching from the west. Gusty
northwest winds then return following a cold front Friday night.

Additional thunderstorms are forecast over the southern
third of Lake Michigan this evening into tonight. A few storms
could be severe with large hail being the primary concern.
Additional storms are possible Friday into Saturday, with a few
stronger storms possible.

CMiller

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058-
     WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067-
     WIZ068-WIZ069-WIZ070-WIZ071-WIZ072 until 7 AM Thursday.

LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-
     LMZ565-LMZ567-LMZ643-LMZ644-LMZ645-LMZ646-LMZ669-LMZ671-
     LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878 until 7 AM Thursday.

&&

$$

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