NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 081729
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1229 PM CDT Sat Aug 8 2026

.KEY MESSAGES...

- Dry and pleasant today with highs in the low 80s.

- Thunderstorm chances return Sunday. There is the potential for
  a late morning to afternoon round, and then an evening and
  overnight round. Strong to severe storms will be possible.
  Uncertainty remains regarding exact timing of the rounds and
  positioning.

- Any storms on Sunday will be capable of heavy rain. Localized
  flooding will be possible, especially where storms repeatedly
  track through the day.

- Multiple rounds of rain and thunderstorms are possible through
  the work week.

&&

.SHORT TERM...
Issued 1229 PM CDT Sat Aug 8 2026

Tonight and Monday night:

A very unsettled pattern arrives late tonight as high pressure
pushes out ahead of an approaching low from the west. This
system will carry some punch with strong WAA in the low to mid
levels and a fairly substantial LLJ and a decent shortwave.
Given some sun ahead of storm development we should see at least
modest instability just ahead of the impending precip, and CAMs
backup the idea that some storm development should be expected
with the best chances further south of I-94 with the better
instability. How long storms persist is in question further
north given less instability but this part of the system should
be fairly progressive with storm activity pushing out by the
late morning to early afternoon. Cannot rule out severe storms
with this either given deep layer shear increasing to 50-60kts.
Altogether there is quiet a bit of uncertainty with morning
convection as the shear may lag behind the convection a bit
which would nix severe risk for the most part in addition to the
uncertainty with instability and the likelihood that storms
would most likely be elevated.

There may be a brief quiet spell in the early to mid afternoon
for a period of recovery before additional ripples in the upper
levels and the continued LLJ and the front all playing a role. A
secondary firing of convection appears likely for somewhere but
exactly where that occurs is still in question. Trends in models
have definitely shifted things a tad south more toward the WI-IL
border but this will be something to monitor as it will determine
how impactful this will be. Where these storms fire will
present an escalating heavy rain and flash flooding risk given
PWATs around 2 inches, west to east propagation and variable
corfidi vectors which is indicative of training convection with
back building. Some storms may become severe as well given
plenty of instability with deep layer shear around 40-50kts,
but the best chances will be on the south side of wherever
storms set up given the better continuous inflow.

CAMs are a bit all over the place with this convection with
uncertainty on where this sets up and for how long, but these
same models are also suggestive of things clearing out late
Sunday night. Into Monday uncertainty grows further but trends
have suggested that the front will sag further south perhaps
taking southern WI out of the primary risks for precipitation
and storms. There remains a chance that the front remains over
southern WI instead of pushing south which would keep the door
open for severe and flooding concerns so we will be closely
monitoring the progression of the front on Sunday into Monday.

Kuroski

&&

.LONG TERM...
Issued 1229 PM CDT Sat Aug 8 2026

Tuesday through Saturday:

As we remain stuck in this pattern with low pressure over Hudson
Bay and high pressure over the southern U.S. with weak shortwaves
in between, the forecast for southern WI will continue to be
uncertain in terms of storm chances and timing. Right now, it
looks like the main 850mb frontal boundary will end up stationed
in northern IL rather than southern WI, but there is still room
for that boundary to wiggle northward at times. That frontal
boundary will be the focus for storm generation from Tuesday
through Thursday morning.

So Monday night/Tuesday morning storms will once again depend on
the Monday storm movement and where the outflow and effective
front land. It will also depend on where the low level jet
develops Mon nt (and the position of the nose of the LLJ). It will
also depend on if there is a shortwave tracking across that
location at the same time in order to help initiate more organized
convection. Therefore, we have highest chances (55-65%) for storms in
the southern tier of counties Tuesday morning and lower chances
(30-45%) in the afternoon. The afternoon scenario would be for
additional storms firing along the stalled outflow boundary
(again, depends on where the morning convection takes it). Wednesday
storm chances are even less certain, but trending downward.

For Thursday through the next weekend, the GFS and ECMWF ensembles
are showing a 500mb height anomoly over the Great Lakes (an upper
trough) which could cause a round or two of storms in southern WI
with the associated frontal passage. That frontal passage could
move through southern WI as early as Wednesday night or as late as
Thursday night. While the ECWMF ensemble suggests that the upper
low is progressive and quickly brings ridging into southern WI by
Saturday 8/15, the GFS Ensemble forecasts that this upper low will
stall over the Northeast through at least the first half of the
following week.

Cronce

&&

.AVIATION...
Issued 1229 PM CDT Sat Aug 8 2026

VFR TAFs expected through tonight with light to modest northwest
winds turning southwest this evening and then south overnight.
Concerns for storms pushing in from the west will increase into
Sunday morning with potential for a few strong storms with MVFR
CIGS and VSBYS possible for a period. Additional chances for
storms across parts of southern WI later Sunday after a break in
the afternoon may lead to additional periods of MVFR/IFR CIGS
and VSBYS with heavy rain and flooding a risk if storms begin to
train over an area.

Kuroski

&&

.MARINE...
Issued 1229 PM CDT Sat Aug 8 2026

Low pressure of 29.5 inches over the Hudson Bay has carried its
cold front across the lake with west to northwest winds behind the
front this morning that will quickly return to southerly by this
evening ahead of the next approaching low pressure system. An
unsettled weather pattern will set up over the Upper Great Lakes
next week where weak waves of low pressure will cross the region
and produce rounds of thunderstorms at times.

Kuroski

&&

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

$$

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