NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 101149
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
649 AM CDT Mon Aug 10 2026

.KEY MESSAGES...

- Mostly dry over southern Wisconsin today. A storm or two may
  occur this evening along the Wisconsin/Illinois border, mainly
  after 6pm. Isolated gusty winds and hail can't be ruled out if
  a stronger storm occurs. Heavy downpours will also be
  possible.

- Periodic chances for showers and thunderstorms are possible
  through the start of the week. The highest chances for more
  widespread strong storm potential over southern WI will be
  Tuesday morning/afternoon.

- Second half of the week is trending drier with near normal
  temps with a more active pattern returning for the weekend.

&&

.UPDATE...
Issued 640 AM CDT Mon Aug 10 2026

Patchy fog has formed this morning. While not particularly
widespread some locally dense pockets will be possible over the
next couple of hours until the fog mixes out.

Recent runs of the rapid-refresh CAMs have hinted at some
potential for a storm or two along the Wisconsin/Illinois
border this evening. Any stronger storm in the environment
would be capable of gusty winds and hail, as well as heavy rain,
as a plume of higher PWATs ranging from 1.8 to 2 inches will
still be parked along a stalled frontal boundary over northern
IL.

CMiller

&&

.SHORT TERM...
Issued 1200 AM CDT Sun Aug 9 2026

Today through Tuesday night:

Warm frontal boundary and surface based instability gradient
remains south of the WI/IL border overnight and continues to be
the focus for strong to severe thunderstorm development through
09z. While not expecting the stronger surface based activity to
move further north through the early morning hours, could see a
few elevated storms perk up again across far southeastern WI as
they tap into the 700mb WAA and MLCAPE. Thus will maintain
20-50% PoPs for this area for another few hours. Otherwise,
expect this activity to wane through the early morning hours and
capping increases.

In additional to the Cheddar Curtain PoP chances, widespread
rainfall from Sunday will contribute to increased low-level
surface moisture paired dewpoint depressions of less than 3
degrees along with light/calm winds will be enough to support
widespread fog development through daybreak across southern WI.
Low-lying areas and creeks/river valleys may see the lowest
visibilities with even isolated pockets of dense fog at times.
However, conditions expected to improve after daybreak as temps
warm.

Looking at a normal August temps today with highs in the lower
80s, but will remain fairly muggy with dewpoints in the upper
60s to lower 70s. While not much in the way of upper-level
forcing, the stalled surface boundary set up overnight in IL may
meander back northward through the day and set up closer to the
WI/IL border. This paired with humid air mass and PWATs between
1.5-1.75 inches could be the focus for additional shower and
thunderstorm development through the day. Main concern for our
CWA is will the boundary lift far enough northward to bring the
higher rain/storm chances into far southern WI. If this boundary
does creep northward then could see late morning development
with upstream convection trekking eastward through the morning
initiating storms along the WI/IL border. Will be similar to
Sunday and strong to severe storm potential remains given
similar environment. However, the 00z CAMs are favoring the
boundary staying to our south through much of the day and
continue to be be more of an IL issue. Nevertheless, will
continue to monitor and see how things evolve through the
morning.

The active pattern over the Midwest will continue into Tuesday
as the upper-level low continues to meander around the Hudson
Bay region. Still seeing signs of another mid-level shortwave
trough rounding the base of the broader trough and tracking
across the Upper Midwest through Tuesday morning. This is a
fairly similar setup to the how things played out with Sunday
round of storms across our neck of the woods. Thus looking at
upstream convection bringing an MCV across the area Tuesday
morning bring heavy, efficient rainfall and strong to even
severe wind gusts if it maintains its strength. However, this
activity will depend on where this lingering boundary sets up
as well as prior days convection, thus the threat remains, but
is conditional. Will have to watch and see how things take
shape over the next 24-36 hours.

Wagner

&&

.LONG TERM...
Issued 1200 PM CDT Sun Aug 9 2026

Wednesday through Sunday:

Continue to see a trend in the global models of the upper-level
low and trough beginning to track eastward into Quebec midweek
and onward. As a result it will shift the active pattern
eastward as well. While cannot completely rule out a stalled
boundary and some shower/storm activity across the area
Wednesday as hints of a mid- level vorticity lobe swings down
the backside of the gradually departing upper-level trough, but
any activity will be highly dependent on the prior days
activity. However by Thursday, surface high pressure begins to
build into the Upper Midwest and continue to build through
Friday as the upper-level ridge axis builds across the central
CONUS. This will bring a drier pattern to southern WI through
the end of the week.

Then the long range models and ensembles trends turn more
active into the weekend as a series of mid-level shortwave
trough as projected to swing across the region. This will bring
a periodic shower and thunderstorm chances across the area
Saturday and Sunday.

Temps in the extended trend toward normal through the middle of
the week before dipping to near or even below normal temps
toward the end of the week.

Wagner

&&

.AVIATION...
Issued 649 AM CDT Mon Aug 10 2026

Patchy fog will linger over the next couple of hours before
mixing out. Then VFR is expected during the daytime hours today
amid light and variable winds. This evening, a storm or two may
impact terminals along the WI/IL border.

Fog then looks possible again tonight amid the light winds and
high near surface moisture.

There is some potential for a thunderstorm complex to move over
southern WI Tuesday morning into Tuesday afternoon, though
timing and uncertainty in the storm track will keep mentions of
this out of the TAFs at this time.

CMiller

&&

.MARINE...
Issued 1200 AM CDT Sun Aug 9 2026

Unsettled pattern is expected for the start of the week as a
frontal boundary meanders across the region. This boundary is
stalled south of Lake Michigan early this morning and is
bringing light and variable winds across the Lake through the
morning into the afternoon. This boundary will also be the focus
for additional shower and thunderstorm development this
afternoon, but mainly looking to impact southern portions of
the the Lake. Will continue to see light and variable winds into
Tuesday as the boundary wobbles back north and as another storm
complex is expected to track along it bringing showers and
thunderstorms across the southern half of the Lake Tuesday
morning and afternoon. Will see another day of shower activity
along this boundary on Wednesday, but then looking at high
pressure to build for the latter half of the week.

Wagner

&&

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

$$

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