NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 101829
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
129 PM CDT Thu Sep 10 2026

.KEY MESSAGES...

- Patchy fog possible in low-lying areas later tonight.

- Isolated showers & thunderstorms possible late Friday night
  into Saturday. Apart from a few lightning flashes, no hazards
  are expected.

- Additional showers & storms expected Sunday night through
  Monday night. Will be monitoring for possible heavy rain &
  severe weather impacts over coming forecasts.

- Becoming seasonable by the middle of next week.


&&

.SHORT TERM...
Issued 130 PM CDT Thu Sep 10 2026

Rest of this Afternoon through Friday night:

Synopsis/Mesoanalysis: High pressure is centered over the Rochester,
MN vicinity this afternoon, with clearing skies and light/variable
winds being observed across southern Wisconsin. Surface heating &
lingering low level moisture have combined to promote fair weather
cumulus development in areas that have experienced the most sunshine
to this point, with cumulus clouds expected to blossom across the
remainder of the region over the next couple hours. Skies will
quickly clear following sunset this evening as the high continues
over southern Wisconsin. Mostly clear skies and light winds will be
favorable for patchy fog development overnight, with the best fog
potential being found in low lying areas. Currently draped over
Saskatchewan, a cold front will work toward the Upper Mississippi
Valley during the day on Friday, encouraging shower and thunderstorm
development well west of the area during the afternoon & evening
hours. Some storms will attempt to to work toward southern Wisconsin
during the second half of the overnight, steadily weakening in the
process. A few of them could reach western areas during the predawn
hours Saturday morning, though their coverage and intensity are
expected to be low.

Tonight: With high pressure lingering in the vicinity, expecting
another overnight period of efficient radiational cooling and
possible patchy fog. Like last night, near-surface moisture will be
quite shallow, so expecting persistent fog potential to remain
confined to low-lying spots and river valleys. Slow down and use low
beam headlights if encountering pockets of fog on the roads late
tonight.

Friday Night: Will be monitoring for isolated showers &
thundershowers during the predawn hours ahead of the approaching
cold front. Expecting weaker storm intensities given the overnight
timing, with severe weather potential appearing very low. Isolated
storm coverage will also keep heavy downpour concerns to a minimum.

Quigley

&&

.LONG TERM...
Issued 130 PM CDT Thu Sep 10 2026

Saturday through Thursday:

Synopsis: An energetic large scale pattern will continue into the
long term period. A surface cold front will vacate to the south and
east of the region Saturday afternoon or evening, bringing chances
for a few isolated showers and thunderstorms in the event sufficient
sunshine occurs earlier in the day. An intermediate area of high
pressure will move through the western Great Lakes Saturday night
through Sunday, bringing pleasant conditions for the end of the
weekend. A second upper disturbance and cold front will move in from
the Northern Plains Sunday night through Monday night, bringing
periods of showers of thunderstorms. Will be monitoring trends for
severe weather and locally heavy rain potential, particularly in any
thunderstorms occurring Monday evening/night. The responsible cold
front will clear south of the area during the day Tuesday, with
arriving high pressure bringing pleasant conditions through
Wednesday night. Rain chances may return by Thursday, though global
guidance remains split over whether this potential will materialize.

Saturday: Will be monitoring timing trends regarding cold frontal
progression through southern Wisconsin, as a slower/later evolution
would open a window for isolated storm development during the
afternoon/early evening. Storm formation would also be dependent on
a period of sufficient sunshine & surface heating in the wake of
earlier day showers/storms, which adds further uncertainty to the
development picture. Range of timing & sky condition solutions
remain apparent in available forecast guidance, which is driving low
(~10-15%) overall precip probabilities in the NBM. Given the noted
uncertainties, have trended precip probabilities toward that of the
NBM in the afternoon update. Will continue to refine this aspect of
the forecast through Saturday morning.

Sunday night through Monday morning: Broad warm advection will be
increasing regionally ahead of the next disturbance, with a
seasonably strong low level jet helping to focus nocturnal shower
and storm development across the mid-upper Mississippi Valley.
Anticipating activity making it into southern Wisconsin near/after
midnight & lingering through at least daybreak Monday. With larger
scale thermodynamic recovery ongoing through this time frame,
expecting instability values to be sufficient for thunder but a
touch marginal for severe weather hazards. As such, expecting any
thunderstorm hazards to be related to locally heavy downpours given
increasing precipitable water values in the 1.2-1.5” range. Will be
monitoring for any training signals in model guidance as this
portion of the period draws closer.

Monday evening through Monday night: A second window of shower and
storm potential will open as a surface warm sector (if it hasn’t
already) spreads into southern Wisconsin in advance of a cold front
& approaching upper wave. Available deterministic precip forecasts &
the broader pattern point toward storm initiation occurring during
the afternoon over Iowa, with activity then moving toward southern
Wisconsin after sunset. Mesoscale details will become clearer
through this weekend, though large front-parallel shear orientations
imply likely upscale growth in storms as they transition into the
CWA. Despite the parallel nature of front-shear vector alignment,
sufficient deep layer shear magnitudes & instability, in addition to
a steadily increasing low level jet, would be factors supporting
storm maintenance into the overnight hours. Will thus be evaluating
arriving high-res guidance for possible severe weather hazards into
this weekend. Even higher precipitable water values in the 1.5-
1.75”+ range would support additional potential for locally heavy
rainfall and some hydro impacts as well, particularly in locations
experiencing training.

Quigley

&&

.AVIATION...
Issued 130 PM CDT Thu Sep 10 2026

VFR flight categories prevail through the period at all southern
Wisconsin terminals. High pressure will continue across the area
tonight, leading to mostly clear skies and light/variable surface
winds. Will be monitoring for pockets of FG development in low lying
areas through daybreak, with confidence in development locations too
low to justify any mentions at this time. Will be monitoring
observational trends into tonight & make amendments if necessary.
High pressure will move east of the area tomorrow, allowing for
increasing southerly winds during the afternoon hours.

Quigley

&&

.MARINE...
Issued 130 PM CDT Thu Sep 10 2026

High pressure near 1020 mb will linger through tonight across the
open waters,  bringing light and variable winds. A new area of low
pressure near 1018 mb will shift from central Canada toward the
Hudson Bay Friday morning through the day Saturday, bringing
increasing south-southwest winds followed by a west-northwest wind
shift behind a cold front. Occasional wind gusts near gale force are
possible during this time frame, though whether or not they will be
widespread enough to warrant headlines remains uncertain. Trends
will continue to be monitored through the end of this
week. Scattered showers and storms will accompany the
approaching/passing front, with widespread severe weather not
currently anticipated.

High pressure near 1020 mb will shift from the northern Great Plains
across Lake Michigan Saturday night through Sunday night, bringing
light and variable winds. The next area of low pressure & cold front
will approach from the west early next week, bringing increasing
winds & additional chances for showers and storms. Depending on the
strength of the low and front, periods of gales & some stronger
storms could be possible. Will be providing additional details as
this portion of the period draws closer.

Periods of Small Craft Advisory conditions are possible in nearshore
zones Friday through Saturday, and once again early next week.
Depending on the strength of the surface low pressure center & cold
front responsible for next weeks winds, some gales could occur. Will
be monitoring trends for possible headlines from late week into
early next week.

Quigley

&&

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

$$

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