NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 130508
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1208 AM CDT Mon Apr 13 2026

.KEY MESSAGES...

- Multiple windows for thunderstorms this week, with each having
  varying degrees of strong to severe potential, beginning
  tonight then each day and night possibly through Thu.

- Heavy rain and flooding potential will increase through the
  week as rainfall accumulates from rounds of showers and
  storms. Srn WI rivers are expected to rise with some reaching
  minor flood stage, and potentially higher levels of flooding.


&&

.SHORT TERM...
Issued 1208 AM CDT Sun Apr 12 2026

Tonight through Monday night:

The widespread light to brief moderate rainfall is expected to
end from west to east across ern WI by 07Z, as the shortwave
trough responsible for the rain moves away across Lake MI.
Meanwhile, farther to the north, cyclogenesis over nrn Ontario
and srn Hudson Bay will support a dominant low developing in
said region, while its cold front shifts ewd across nrn WI. The
front will weaken and stall over central or srn WI by 12Z Mon.

The front will then move back to central WI as a warm front
during the afternoon as sly winds increase over srn WI. The sly
winds are a result of low pressure tracking ewd along the SD
and NE border. Very steep mid level lapse rates around 8C/KM
will overspread srn WI, capping a very mild and moist airmass.
The return of low level moisture beneath the cap will simply
result in widespread stratus and possibly even patchy drizzle by
later in the day. Have lowered Max temps a bit to account for
this.

A weak shortwave trough will then track from the central Great
Plains to srn MN by 00Z Tue, then across nrn WI Mon nt. This
will shift the low pressure area and the nose of a strong low
level jet across central WI. The warm sector will be strongly
capped but right along and north of the front, convective
initiation and severe convection is likely. There are
differences among the models on the aforementioned features, but
the CAMs and 00Z HREF trended north with the deep, moist
convection. Some CAMS then suggest a MCS will slip esewd into
central WI and possibly se WI from the late evening into the
early morning hours. MUCAPE will range from 1500-2000 J/KG with
mdt effective shear present. Damaging winds would be the main
threat but cannot rule out the possibility of QLCS tornadoes if
the MCS maintains maturity.

Gehring

&&

.LONG TERM...
Issued 1208 AM CDT Sun Apr 12 2026

Tuesday through Sunday:

A stationary front will reside in the vicinity of srn WI on Tue
into Tue evening, while a vorticity maximum approaches in swly
flow aloft. In the lower levels, low pressure will track across
the central Great Plains into ern NE with the nose of a strong
low level jet developing into srn WI. MLCAPE around 2000 J/KG
and mdt deep layer shear is expected, and with the aforementioned
lift, the cap is expected to erode. Scattered to numerous
strong to severe convection will ensue either late afternoon or
early evening and continue to expand. Large hail and damaging
winds will be the primary threat with lesser chances for a few
tornadoes.

A more organized shortwave trough will then approach from the
southwest Wed nt, but not before a vorticity maximums lifts nwd
ahead of it into se WI by late Wed afternoon. Thus additional
rounds of showers and storms are expected from Wed afternoon
through the night. Some showers may linger on Thu as the
shortwave trough passes in the morning.

Yet another larger and stronger upper trough and n-s sfc trough
will move out of the Great Plains and into the wrn Great Lakes
for Fri nt-Sat. In summary, multiple rounds of showers and
storms are forecast from Tue-Sat, with a few inches or more of
rain possible. River rises are expected with some flooding
possible. Some severe storms will likely occur at times.


Gehring

&&

.AVIATION...
Issued 1208 AM CDT Sun Apr 12 2026

LLWS via a swly 40-45 kt low level jet early this morning is
expected. Otherwise, widespread MVFR Cigs and areas of Cigs
below 1 kft developing early this morning. The widespread
rainfall will end from west to east across ern WI by 07Z Mon.
Areas of MVFR Vsbys expected within the rainfall, but areas of
MVFR Vsbys via BR may also form toward sunrise over south
central WI. Some clearing skies may occur toward central WI
toward sunrise Monday and continue into the early afternoon.

Elsewhere across srn WI, Cigs below 1 kft will rise to MVFR
Cigs with widespread MVFR Cigs spreading from srn WI into
central WI during Mon afternoon. Patchy drizzle or very light
rain may develop. LLWS will redevelop on a swly low level jet of
45-50 kt by late evening along with with chances for
thunderstorms especially toward central WI. Finally, areas of
Cigs below 1 kft may develop over south central WI late Mon nt.


Gehring

&&

.MARINE...
Issued 1208 AM CDT Sun Apr 12 2026

A broad area of low pressure around 29.4 inches over Ontario
becoming deeper over southern Hudson Bay early this morning.
This will bring breezy south winds to all of Lake Michigan, but
with gales expected over the north third into early this morning.
A Gale Warning is in effect.


Winds will weaken later this morning as the low quickly moves
away and the trailing cold front stalls over central Lake
Michigan. Then, a couple passing low pressure system along the
stalled front will lead to intermittent showers and
thunderstorms through the middle of the week. Areas of dense fog
will likely occur at times due to a relatively mild and humid
airmass over the cold waters.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 until
     3 AM Monday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM
     Monday.

&&

$$

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