110
FXUS63 KMKX 191058 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
558 AM CDT Sat Sep 19 2026

.KEY MESSAGES...

- First round of heavy rainfall has pushed south of the area,
  with lingering moderate rainfall into this morning. Area of
  heavier rain to the west should remain west and southwest of
  the area into this morning. May see a brief lull before the
  next round moves in by midday/early this afternoon.

- Additional storm development is possible this afternoon,
  particularly along and south of Interstate 94. Additional
  heavy downpours and flooding impacts would be the main
  concerns, with an isolated strong storm possible near the
  Wisconsin/Illinois border.

- Prolonged period of high swimming risk conditions continues
  into Tuesday at all Lake Michigan beaches, and may need to be
  extended into Wednesday evening.

- Off and on chances for lighter rain Sunday into Monday.
  Trending drier Tuesday onward.

&&

.UPDATE...
Issued 558 AM CDT Sat Sep 19 2026

The first round of heavy rainfall as pushed south of the area,
with lingering moderate rain over most of the area. This
activity should linger into middle morning with lingering warm
air advection, before a possible lull in the activity by later
this morning occurs.

There are additional showers and storms with heavy rainfall
remaining to the west and southwest of the area early this
morning, closely tied to the southwesterly low level jet nose
and frontogenesis response near 850 mb. These features are
expected to gradually veer southeast through the morning, which
should mainly miss or just clip far southwest parts of the
forecast area. Will continue to monitor for flash flooding and
other flooding impacts in this area into this morning.

A 500 mb shortwave trough helping along an area of showers and a
few storms in western Iowa should push east northeast into the
area by midday into the afternoon. This feature, along with the
close proximity of the surface low and warm front just to the
south of the area, should bring another round of showers and
some storms this afternoon into early this evening. An isolated
strong storm may occur near the Illinois border, though this is
a small (under 20 percent) chance, as it should remain cloudy
all day and limit any potential instability from developing.

The better potential for heavy rain and flooding should mainly
in southern portions of the area, where the Flood Watch remains
in effect until 7 PM CDT this evening. It would not take a lot
of additional rainfall to cause some flooding issues, especially
in urban areas, so will continue to monitor this potential.

The Beach Hazards Statement for a high swim risk remains in
effect through early Tuesday evening for all beaches along Lake
Michigan from Sheboygan to Kenosha Counties. The combination of
gusty onshore winds and high waves will bring the high swim risk
conditions. Stay out of the water and away from dangerous areas
like piers and break walls. This may need to be extended into
Wednesday evening, if the high waves persist.

Wood

&&

.SHORT TERM...
Issued 1055 PM CDT Fri Sep 18 2026

Current Overnight through Sunday:

Synopsis/Mesoanalysis: Weak area of surface low pressure continues
to move into west-central Iowa late this evening. Rooted in the 850
mb layer, warm advection is blossoming along the northeast periphery
of the surface low, combining with an east-west band of
frontogenesis & bisecting low level jet to spark widespread
showers and storms from near the Dells westward. This activity
will slide east-southeast into the region after midnight,
persisting into the first half of Saturday morning. The
showers/storms will bring moderate to torrential downpours,
with flash flooding possible in locations where the heaviest
rates track repeatedly. Activity is expected to slide southeast
of the area by mid-day Saturday, with the forecast picture
becoming more uncertain thereafter. The low currently over Iowa
will approach or pull just south of the Wisconsin-Illinois
border through the afternoon & early evening, with continued
warm advection along its northern periphery posing at least
conditional potential for additional showers and storms near and
south of I-94. Storm development and coverage will be dependent
on thermodynamic recovery in the wake of morning precip, in
addition to any embedded disturbances in the flow aloft. In the
event development occurs, additional heavy downpours and
flooding impacts would be possible. Given the conditional
potential for additional afternoon storm development, the Flood
Watch has now been extended until 7 PM Saturday evening over the
southern half of the area. Further north, the Flood Watch
remains in effect until 1 PM Saturday. Stay vigilant for
possible Flood and Flash Flood Warnings through Saturday
afternoon, and never drive through flooded roadways.

Rest of Overnight into Saturday morning: Expecting widespread
showers and storms across southern Wisconsin. Storms will bring
varying rainfall rates of moderate to torrential intensity, with
widespread precip coverage & long precip duration posing the
potential for at least minor hydrologic impacts (urban/small stream
flooding, ponding of water on roads, and minor rises on rivers)
areawide. Flash flooding will be possible in locations where the
heavier rates track repeatedly. Environmentally, the most favorable
corridor for flash flooding impacts will align near & west of a
Kenosha-Watertown-Wisconsin Dells line through early Saturday
morning. It will be in this part of the area that 1) sufficient
MUCAPE & embedded convection will allow for the materialization of
heavy to torrential rainfall rates and 2) elongated southeast-
northwest frontogenesis bands and their intersection with the low
level jet will provide focus points for training to occur.
Collectively, the going forecast of widespread 1-3" rainfall
accumulations with locally higher totals in the 3-6"+ range remains
on track, with the corridors of higher totals most likely along/west
of the Kenosha-Watertown-Wisconsin Dells line. Flood Watch thus
remains in effect into Saturday morning.

Saturday afternoon & evening: A more conditional window of
additional storm development will be in place predominantly along
and south of I-94 as low pressure moves near or just south of the
Wisconsin-Illinois border. Sufficient recovery post-AM precip will
be essential for this development to occur, with an additional
trigger from any passing disturbances aloft likely being needed as
well. Water vapor imagery shows one such disturbance nearing the
Nebraska Sandhills at the current hour, with crude extrapolations
bringing it across southern Wisconsin from ~11 AM - 7 PM Saturday if
it manages to hold together. Suspect that it`s this feature that
more active 00Z CAM solutions are latching onto given its estimated
arrival time & the timing of their simulated storm re-development.
Will thus be monitoring trends very closely through tomorrow
morning, as little additional rainfall would be required to create
additional flooding problems. Have thus extended the Flood Watch
through 7 PM Saturday across the southern half of the area. Severe
weather potential would be low in any re-development, though an
isolated storm with gusty winds wouldn`t be entirely out of the
realm of possibility near the Wisconsin-Illinois border.

Quigley

&&

.LONG TERM...
Issued 1055 PM CDT Fri Sep 18 2026

Sunday night through Friday:

Strong high pressure centered just north of the Great Lakes will
very gradually shift eastward Sunday night through Wednesday. A
cooler and much drier airmass is expected across southern Wisconsin
through this period under the influence of the high and an upper
level troughing pattern. Below normal high and low temps are
anticipated through mid-week.

Latest forecast models suggest the upper level trough and surface
high will maintain enough of an influence across southern Wisconsin
for continued mainly dry weather late week next week, with
temperatures gradually returning to near normal by the end of the
week as upper level ridging begins to build in from the west.

DDV

&&

.AVIATION...
Issued 558 AM CDT Sat Sep 19 2026

The first round of heavy rainfall as pushed south of the area,
with lingering moderate rain over most of the area. This
activity should linger into middle morning, before a possible
lull in the activity by later this morning occurs. Ceilings
below 1000 feet AGL and visibility of 1 to 4 miles are generally
expected this morning, with gusty southeast winds gradually
weakening.

There are additional showers and storms with heavy rainfall
remaining to the west and southwest of the area early this
morning. This activity should mainly miss or just clip areas
southwest of Madison.

Another round of showers and some storms should occur this
afternoon into early this evening across the area. The better
potential for heavy rain should be for Madison and Milwaukee and
south. Lighter southeast to east winds are expected this
afternoon, as low pressure passes by to the south. Ceilings
should remain below 1000 feet AGL this afternoon and early
evening, with 1 to 4 mile visibility within the showers and
storms.

Showers and a few storms should linger into the evening,
gradually pushing southeast of the area later tonight into early
Sunday morning. Winds will become east to northeast and increase
by Sunday morning. Ceilings should remain below 1000 feet AGL
into early Sunday morning, before rising to above 3000 feet AGL
by Sunday afternoon. Visibility should be in the 1 to 4 mile
range until the rain moves out of the area.

Wood

&&

.MARINE...
Issued 558 AM CDT Sat Sep 19 2026

Low pressure around 29.8 inches will move east northeast toward
far southern Lake Michigan today, then just south of the
southern portions of the lake tonight. Winds will become
southeast and gusty ahead of the low, then shift northeast
tonight as the low passes to the south. Areas of widespread
showers and thunderstorms will accompany the passing area of low
pressure today into tonight.

Gusty east to northeast winds are then expected Sunday through
Monday night, as low pressure slowly moves into the Ohio River
Valley. High pressure around 30.5 inches will move southeast
into Ontario during this period. Gusts could occasionally
approach gale force Sunday into Monday night, mainly over
southern portions of the lake. Winds will steadily taper Tuesday
through Wednesday, as the high pressure system moves into
Quebec and New England.

A Small Craft Advisory is in effect through early Tuesday
evening for the nearshore waters of Lake Michigan, for the
combination of gusty onshore winds and building waves through
this period. This may need to be extended into Wednesday
evening, if the high waves persist.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071-WIZ072
     until 7 PM Tuesday.

     Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058-
     WIZ059-WIZ060 until 1 PM Saturday.

     Flood Watch...WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-WIZ067-WIZ068-
     WIZ069-WIZ070-WIZ071-WIZ072 until 7 PM Saturday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM
     Tuesday.

&&

$$

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