NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 141554
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1054 AM CDT Fri Aug 14 2026

.KEY MESSAGES...

- Mainly dry through today. An isolated shower is possible near
  the Wisconsin-Illinois border.

- Potential for storms to lift into southern WI tonight into
  Saturday morning (50-80% chances) delivering a soaking
  rainfall. Note that there is also a chance (20-50%) for this
  activity to miss us entirely, tracking elsewhere through the
  Midwest.

- Additional shower and storm chances Saturday night into
  Sunday, but severe storm potential and rain amounts have
  trended lower.

- Drier and more comfortable into early next week, with storm
  chances returning by midweek.

&&

.UPDATE...
Issued 1055 AM CDT Fri Aug 14 2026

Have pulled back on precip probabilities through this afternoon
given ongoing and anticipated trends.

Current water vapor imagery shows an MCV over the Missouri
Valley, with a compensating area of shortwave ridging in place
immediately downstream/over southern Wisconsin. Surface
observations reveal a bifurcated frontal pattern regionally,
with a warm front draped over central Iowa, and an
effective/convectively-modified boundary extending from the
Missouri-Iowa border southeast to the Ohio River. Placement of
boundaries is leading to a "zoned" warm sector, with modest
instability values in place along/south of the warm front & more
extreme values restricted to the south of the southern
boundary. Driven in large part by 850-700 mb warm advection
north of the warm front, a prior band of showers is decaying
over northeast Iowa & northern Illinois as it encounters the
shortwave ridging/subsidence in place over southern Wisconsin.

With the initial/leading band of showers falling apart, and the
MCV-related forcing & warm sector not pulling into the area
until this evening, have thus reduced precip probabilities
through 7 PM, with a now entirely dry forecast prevailing
through the afternoon across the majority of southern Wisconsin.
Have maintained some ~15-30% values near the WI-IL border, where
a light shower can't be entirely ruled out as better forcing
begins to approach. Expect better rain chances post-sunset. Will
be discussing this potential in greater detail in the early
afternoon update.

Quigley

&&

.SHORT TERM...
Issued 1250 AM CDT Fri Aug 14 2026

Today through Saturday:

The existing line of thunderstorms spanning from east IA to
central IL should slowly sag southward through the predawn
hours this morning, leaving us with dry weather. A decaying
complex of storms originating from IA may clip far southwestern
WI post-dawn this morning based on 00z CAM guidance (20-50%
chance, mainly for Lafayette and Green county only), though
instability would be extremely limited if it even makes it here
(likely not enough for thunder, but included slight chances to
play it safe). Additional shower and storm activity near and
south / southwest of the state border will continue through the
daytime hours today, with slight chances for a stray cell to
drift and decay into our region.

Higher and more widespread chances for showers and thunderstorms
arrive tonight into Saturday morning as weak low pressure lifts
northeast from KS, but there is plenty of uncertainty on how
this will play out. I really mean it when I say "uncertainty"
this time... check out the 14.00z HRRR: two nocturnal convective
complexes initiate, one crashes through northern IL, the other
through far northwest WI, and southern WI gets dry weather. Then
for another scenario, check out the 13.21z RAP, 14.00z NAM and
NAM NEST, the southern convective complex crashes into southern
WI and delivers widespread rainfall lasting through early
Saturday afternoon. In either scenario, instability is very
limited (HREF mean MUCAPE below 500 joules). Not expecting any
strong to severe storms, just efficient rainfall if applicable.

Sheppard

&&

.LONG TERM...
Issued 1250 AM CDT Fri Aug 14 2026

Saturday night through Thursday:

Weak low pressure continues east from the Great Lakes region on
Sunday, likely deepening slightly and dragging a cold front across
WI. The exact arrival time for the front is not yet certain, but
the initial NW wind shift is currently favored for the early morning
(predawn) hours, followed by the arrival of lower dewpoints
(low 60s or potentially even 50s) on these same winds and / or a
secondary backdoor cold front (with NE winds) Sunday afternoon.
In the 500mb pattern, we do have a 500mb shortwave trough that
could phase well with the warm sector over IN / IL Sunday
afternoon, but that doesn't leave us much to work with in
southern WI. A round of showers or weak thunderstorms along the
initial frontal passage Saturday night into Sunday morning would
also (potentially) leave some cloud cover to interfere with
peak heating, limiting the instability when the afternoon
secondary baroclinic zone / backdoor cold front arrives. All
this to say Sunday's storm setup leaves a lot in question, but
the odds of any strong to severe storms are relatively low for
now. Overall rain chances 50-65%, peaking early Sunday morning
and tapering into the afternoon.

Predominantly dry weather expected Sunday night into Tuesday
morning as high pressure passes overhead, with temperatures near
seasonal norms. Shower and thunderstorm chances return late
Tuesday through midweek as a surface trough of low pressure sweeps
east across the midwest.

Sheppard

&&

.AVIATION...
Issued 655 AM CDT Fri Aug 14 2026

Fog and lower ceilings this morning may linger for another hour
or so, but will lift as temps warm and easterly winds increase
through the morning. While cannot rule out a stray shower in
southwestern or south-central WI today, expecting mostly dry
conditions and breezy easterly through the afternoon. Then this
evening looking at shower chances increase from southwest to
northeast later this evening into Saturday morning with moderate
to heavy rainfall and better thunderstorm potential along with
lower flight conditions for areas closer to the WI/IL border.

Wagner

&&

.MARINE...
Issued 1250 AM CDT Fri Aug 14 2026

Synopsis:
Multiple rounds of storms are expected to cross the southern
portion of Lake Michigan into this weekend due to a front that
remains in place south of the lake. Low pressure of 29.7 inches
over Kansas will track to the northeast and east toward southern
Lake Michigan into tonight and Saturday. This low should help
to bump up winds and waves across the southern two thirds of
Lake Michigan into Saturday. Beyond this system, a broad ridge
of high pressure of 30.1 inches will push into the Great Lakes
early next week before another potential front moves through the
region midweek.

Nearshore Zones:
Breezy southeast winds and building waves are expected late
tonight into Saturday, with Small Craft Advisory conditions
possible.

Sheppard

&&

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

$$

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