NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 090540
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1240 AM CDT Sun Aug 9 2026

.KEY MESSAGES...

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

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

- Periodic chances for showers and thunderstorms are possible through
  the first half of the week.

&&

.SHORT TERM...
Issued 1240 AM CDT Sun Aug 9 2026

Today through Monday night:

Well... what an interesting hand we have been dealt today. Meso
models have started to converge on a scenario for this morning and
evening that favors a more robust round of morning convection with
weaker evening potential. This convergence of the meso models does
track well with the mid level and upper level shortwave and WAA.
With the synoptic forcing better aligned with guidance there is a
bit more confidence here, but for any MCS type system guidance will
never full grasp the full picture.

With storms starting to develop in in the Dakotas and western
Minnesota, this leaves us with one likely scenario with a few
contingencies. The likely outcome which favors models like the
FV3, Nam NEST, and HRRR has storms developing out west and
congealing into a n-s line that should move into southern
Wisconsin during the mid to late morning hours then exit to the
east during the early afternoon. The later timing does allow for
some instability to move into the area with good moisture, lift
and shear. Bulk shear remains around 40 kts or greater and the
LLJ keeps good WAA ahead of the line. This will therefore lead
to a stronger signal for strong to severe storms in the morning.
Now some guidance is far more robust with the instability than
others (HRRR could be considered a worst case scenario 00z run).
With more of a linear storm mode, this will open the door for
tornadic potential. Strong winds remain the larger hazard with
small hail possible. How much of a wind and tor threat this
becomes will entirely depend on the amount of instability we
have. The more instability the more widespread the severe risk
the less instability the more this is may a few downburst type
splats along the line.

With this later arrival time being favored, this looks to wash out
the window for an adequate afternoon recovery period. If that
is the case then the better instability gets shunted further
south into IL. This then favors an evening round beginning to
fire roughly along the WI/IL border or further south. The
uncertainty here in location still remains high. The mesoscale
environment will need to be watched closely as there are still
models that hint at the LLJ and strong WAA being able to
overcome that short window of time to bring storm chances back
north toward I-94. So were not completely out of the woods yet.
In the event that storms do develop in the evening along or
south of I-94, heavy rain will be the main concern. There could
be a few downburst winds in isolated areas, but PWATs will be
around 2 inches. The east to west orientation of the line
developing with corfidi vectors that indicate training
convection, means flooding will be a major concern where ever
this develops.

So TLDR is uncertainty does remain, but trends are highlighting
a more robust morning round of convection that lingers into the
afternoon. Then evening storms along the WI/IL border or
further south. If storms move through earlier in the morning and
are weaker, then the door is fully back open for evening storms
across southern Wisconsin. Stay up to date with the weather
today as the mesoscale environment will throw curve balls at
this scenario. Have a way to receive warnings.

Beyond this, we can look ahead to Monday which remains uncertain
(our favorite word of the week it seems). Under the zonal flow aloft
with multiple shortwaves and CAMs spitting out many solutions its
the name of the game. This time the question becomes where will
the sfc front end up and will it stay there. Its possible that
with todays activity (if it plays out how its trending), that
the sfc boundary remains just to our south and keeps with it the
better severe potential and flooding threats. If this front
remains stretched across southern Wisconsin or moves back north
into the area, then the warm (southern) side of the front will
be in play for severe and flooding, while the cooler (northern)
side of the front is spared from the worst of it. If the trends
hold, then much of the rain looks to stay in IL until Monday
evening/night.

Patterson

&&

.LONG TERM...
Issued 1240 AM CDT Sun Aug 9 2026

Tuesday - Saturday

A flattened upper-level cutoff low continues to meander around the
Hudson Bay region to our north on Tuesday. Given the persisting
pattern, could see another embedded shortwave trough round the base
of the longwave trough on Tuesday to bring additional shower and
thunderstorm chances to our neck of the woods as suggested by the
latest global models. Similar to the pattern for the next two days,
chances, strength, and location of this activity will depend on the
timing of the upper-level wave pairing with the low-level
front/instability gradient placement, which are subject to shift due
to prior days convection/pattern. Nevertheless, as multiple NCAR AI
NWP forecast ensembles suggests, the potential remains for some
storms for Tuesday.

Then for the midweek, we begin to see the upper-level low begin to
move east-southeast into Quebec shifting the more active pattern
further east. Northwesterly upper-level will to linger on the
backside of the departing trough and as a result looking at a drier
stretch for the second half of the week as the GEFS and EPS
ensembles become more aligned with the upper-level ridge
beginning to build across the northern Plains and into the Upper
Midwest into next weekend.

Temps in the extended are trending toward normal through the first
half of the week, but hints of near to even below normal temps
toward the end of the week.

Wagner

&&

.AVIATION...
Issued 1240 AM CDT Sun Aug 9 2026

VFR condition will continue into the early morning hours. A line
of storms are expected to move through southern Wisconsin this
morning and again this afternoon which could bring MVFR to IFR
conditions. Heavy rain will be possible with each round of
storms which could drop visibilities to 1-3 SM. Any training
storms could lead to flooding concerns. The timing of the first
round looks to move through during the mid to late morning hours
for western terminal and could linger into the early afternoon
for eastern terminals. There is uncertainty on how much back
building rain occurs behind the leading line so stuck to a brief
PROB30 period to cover that uncertainty vs a prolonged
rain/storm time. There is a potential for strong to severe
storms with this morning round. Strong winds is the main hazard.
Can't rule out a brief tor or small hail.

For terminals north of Interstate 94, the morning round may
very well be all the rain/storms you get. For terminals along
and south of Interstate 94, the placement of the evening round
is uncertain. Opted for the most recent trend among guidance,
which has the evening round developing along the WI/IL border
or further south. So kept rain mentions out of MKE, UES, and
MSN for now. This may change depending on how robust the morning
round of storms is. Wherever the evening round develops heavy
rain and flooding will be a concern.

Light southwest wind will become breezy by late morning. Winds
will turn to southerly by late morning with a potential for
lakeshore areas to see southeast winds for a brief period of
time. Light and variable winds are expected late this evening
through tonight.

Patterson

&&

.MARINE...
Issued 1240 AM CDT Sun Aug 9 2026

Low pressure across the Hudson Bay will slowly move east toward
Maine today while a second low in the central Plains advances
east toward the southern Great Lakes Region. An unsettled weather
pattern will set up over the Upper Great Lakes all week where
weak waves of low pressure will cross the region and produce
rounds of thunderstorms at times. The firs round of storms
should arrive across the southern and central portion of the
lake late this morning into the afternoon. A second round of
storms is expected to develop across the southern third of the
lake this evening into tonight. Heavy rain will be possible with
each round of storms.

Southwest winds early this morning will become southerly by mid
to late morning and become breezy. Winds then become light and
variable across the lake tonight through Monday. Northeast to
east winds develop across the lake Tuesday and remain light.
Wind direction could become variable at times Tuesday.

Patterson

&&

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

$$

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