187
FXUS63 KMKX 181547
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1047 AM CDT Mon Aug 18 2025

.KEY MESSAGES...

- Beach Hazards Statement in effect for waves of 3-6 feet
  through the early afternoon.

- Multiple rounds of showers and thunderstorms possible through
  early Tuesday morning. Lightning and heavy rainfall are the
  main concerns this morning into tonight. Localized damaging
  winds are an additional concern this afternoon and evening.

- River rises will greatly depend on where the heaviest rain
  occurs this morning through Tuesday morning, with rises to
  minor flood stage if rain falls in our most saturated regions.

- Drying out and becoming less humid by Wednesday.


&&

.UPDATE...
Issued 1045 AM CDT Mon Aug 18 2025

Focus for the thunderstorm activity continue to the upstream
with the decaying line and MCV over IA. There is a healthier
looking storm moving into Iowa County late this morning along
the outflow from the overnight convection. Continue to see more
development southward along the outflow boundary on the northern
fringes of the instability gradient. While cannot rule out
stronger storm or two with gusty winds and a brief spin up along
this, it is coming through earlier than expected and given
clouds ahead of it the environment the instability has not had
as much time to build in to support stronger storms. This looks
to be be the main challenge for today is will the environment
build enough instability to support strong storms. Right now the
better environment looks along and south of the WI border where
the clouds have cleared and the sun is out warming things up
enough.

Some models do ping redevelopment behind the initial line as
the mid-level shortwave and MCV across northwest IA swings
through, but the questions remains on if the environment can
recover from the late morning round as stratus clouds and rain
linger behind the initial line. If we are able to clear another
line of storms with strong, gusty winds would be possible into
this evening, more likely south of I-94 where clearing is most
likely to occur. Should see this activity clear the area later
this evening as the shortwave trough pushes east and a cold
front gradually spreads through the area.

Otherwise given the tropical airmass and saturated grounds,
heavy rain is expected to accompany this activity. Luckily this
initial round of showers and storms is progressive and has not
been sitting over the same area. However if we do see rain sit
over the same area or receive multiple rounds with the
potential redevelopment later this afternoon/evening over
similar area, could see flooding concern increase. This includes
urban flooding as well as rises on local rivers.

Wagner

&&

.SHORT TERM...
Issued 145 AM CDT Sun Aug 17 2025

Today and Tonight:

Lingering activity early this morning continues to drift east
from the remnant from a complex that pushed across the Central
Plains yesterday. Given the instability gradient remains largely
pinned to southwest WI with limited instability north of that we
expect some lightning but likely remaining limited especially
further north. Early this morning some low to mid level
isentropic upglide and mild WAA may continue to keep some
showers going across parts of west central WI for the next few
hours.

Later this morning attention will turn toward the MCS pushing
across southeast ND/northeast NE. Models continue to be all over
the place with exactly how this will pan out with various
solutions bringing different results to southern WI. Some models
track this all the way through southern WI during the late morning
and early afternoon while others have the MCS essentially dying
off leaving southern WI on the drier side through the morning
and early afternoon (outside of some shower activity in central
WI). How this plays out will likely effect the afternoon
instability recovery. While severe storms are not expected even
if this does push through during the late morning and early
afternoon there will still be a risk for heavy rain with this
however with PWATs over 2 inches. Fortunately any storms/heavy
rain will likely be fairly progressive and push out quickly.

Into the late afternoon and evening the expectation will largely
be driven by the morning/early afternoon convection. With some
level of recovery expected and increasing southerly flow with
the surface low/front in northern WI there is expected to be
some level of storm activity with uncertainty primarily coming
from exactly how any remnant boundary/MCV from earlier sets up
in addition to the surface cold front. Most of the instability
today looks likely to be focused across southern and southwest
WI with limited instability as you go north. Cannot rule out a
severe storm or two with decent deep layer shear and plenty of
instability but this will likely be restricted to southwest and
southern WI. This potential is primarily driven by the possible
initiation of storms developing into another MCS from the
remnant boundary/MCV from earlier in the day.

There will be continued shower/storm chances into the overnight
hours in association with the front but will not really carry
much, if any, severe risk. The primary concern for the late
afternoon through the overnight period will continue to be the
heavy rain risk with PWATs still around 2+ inches. These storms
again look likely to be progressive but the flooding risk will
come if certain localized areas or already vulnerable areas are
hit with multiple rounds of heavy rainfall.

In addition to these concerns, a Beach Hazards Statement remains
in effect now until 3pm today for onshore waves from 3 to 6
feet from breezy onshore winds. Expect dangerous swimming
conditions especially for areas near piers and/or breakwalls
which will be most vulnerable to these dangerous currents.

Kuroski

&&

.LONG TERM...
Issued 145 AM CDT Sun Aug 17 2025

Tuesday through Sunday:

A welcome pattern change on the way as the upper level pattern
becomes a bit more amplified and northwest flow allows surface
high pressure to build in from the north and northeast.

The airmass change looks to take a bit of time Tuesday into
Tuesday night as cyclonic flow gradually takes over. Residual low
level moisture and diurnal instability suggest widely scattered
showers and perhaps a few storms developing and moving south
Tuesday afternoon. Have introduced low PoPs for this potential,
which should end shortly after sunset.

Airmass change begins in earnest Tuesday night, with a good drop
in temperatures with lows around 60 (give or take) each night
Tuesday night through Friday night. Highs will drop back into the
70s Wednesday and Thursday, warming briefly back into the 80s
Friday before a reinforcing shot of cooler air arrives for the
weekend. Will need to monitor for rain chances with a frontal
passage late Friday/Friday night, but aside from this boundary,
little if any rain is expected during the extended forecast.

Gagan

&&

.AVIATION...
Issued 1045 AM CDT Mon Aug 18 2025

Widespread stratus deck persist across southern WI terminals
this evening bringing a mix of IFR and MVFR ceilings. Will see
this continue through the early afternoon. However a narrow line
of showers and storms are rolling across the area and bring
brief heavy rainfall and lightning. Looks to reach JVL and MSN
between 16-18z before sliding east. Some lingering low clouds
and showers may persist behind this line, but some additional
redevelopment is not out of the question later this afternoon
and evening. Expect southerly winds ahead it, but should see
winds turn more westerly later this evening behind this
activity as a cold front slides through the area.

Wagner

&&

.MARINE...
Issued 145 AM CDT Sun Aug 17 2025

The onshore winds will create high waves and a Small Craft
Advisory is in effect.

Low pressure will continue to exit toward the Atlantic tonight
with high pressure around 30.4 inches developing across Ontario. A
developing low pressure over South Dakota will move into southern
Minnesota overnight. A front associated with this low pressure
will gradually move southeast across the region, clearing the
south end of Lake Michigan by midday Tuesday. This front will
bring multiple rounds of showers and storms from tonight through
Monday night.

Winds will shift northeast to southeast this morning. A small
craft advisory remains in effect until 1 PM today for these
onshore winds and resulting waves. After the front exits the area,
winds will shift to the north from Tuesday through Friday.

Gagan

&&

.HYDROLOGY...
Issued 145 AM CDT Sun Aug 17 2025

A few more rounds of showers/storms will maintain a locally heavy
rainfall threat through Monday night. Area rivers (particularly
in the Milwaukee metro area and surrounding counties) will be
monitored for potential rises.

Gagan

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060-WIZ066-WIZ071-WIZ072
     until 3 PM Monday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 3 PM
     Monday.

&&

$$

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