228
FXUS63 KMKX 150757
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
257 AM CDT Fri Aug 15 2025

.KEY MESSAGES...

- Most rivers have crested and are trending downward except on
  the southern end of the Fox River. Rivers could rise again
  this weekend into early next week as multiple rounds of storms
  appear possible.

- Active weather returns from as early as Friday night through
  the beginning of next week, with multiple rounds of showers
  and storms forecast. Locally heavy rainfall is possible, most
  likely in the overnight hours Saturday night, Sunday night and
  Monday night.  Lots of uncertainty for if/when storms occur.

- Heat and humidity briefly returns Saturday, especially across
  the southern half of the area.

- Drying out and becoming less humid by mid to late next week.

&&

.SHORT TERM...
Issued 257 AM CDT Fri Aug 15 2025

Today into Saturday:

Main focus is on the convective trends tonight with uncertainty
being the main word through the weekend.

Starting out this morning, there`s some scattered rain showers
tracking eastward across SW Wisconsin along the leading edge of
the low level moisture gradient and a weak mid level shortwave
trough. These may hold on through eastern Wisconsin through
daybreak but coverage should lessen as it pushes into the
surface ridge.

As this feature tracks to the east, southerly low level flow
will be on the increase and start the rise of surface dew
points/low level moisture across southern Wisconsin. Once the
isolated showers move through this morning, the rest of the day
is expected to be dry until tonight. The mid level shortwave
trough currently over central South Dakota/Nebraska will
propagate eastward along the northern fringe of the upper level
ridge and into western Wisconsin this evening. The 15.06z RAP
shows this mid level trough as well as some weak low level
925-850mb moisture transport angled from Iowa to the northeast
into central WI. Thinking that whatever convection/rain develops
follows this flow from the SW to the NE this evening and
overnight moreso into central WI. There`s a decent chance that
this leaves far southern WI dry for a portion tonight with the
better focus on central WI. Thinking the SPC Day 1 outlook is
grabbing the right area for the better risk as the main thing
southern WI has going for it is some decent instability with
2000 J/kg+ SBCAPE developing tonight. Despite the mid level
shortwave coming in, there isn`t much in the way for an increase
in winds with the feature, thus limiting the available wind
shear. Isolated severe with the potential for heavy rainfall
looks like what we`re looking at for tonight. That said, there
are models (like the 15.00z GFS) which develop an MCS in central
WI and drops it straight south into southern WI going into
Saturday morning, so will have to watch for that and short term
trends.

Going into Saturday, the low level jet weakens during the day,
which should lead to a break for at least a portion of the day
before more convection develops later in the day. Conditions
will become very humid with surface dew points getting into the
mid 70s. The past few runs of the HRRR seem to be underdoing
these dew points while most of the other guidance appears to be
overdoing it with them jumping into the upper 70s. This leads to
uncertainty with how convection will develop going into the
evening, but the overnight periods going into early next week
appear to be the main times for stalled/slow moving
thunderstorms with heavy rainfall. It`s mainly a matter of where
it sets up and how intense. Each day going forward will depend
on what happens the day before with boundaries getting pushed
around...thus confidence is on the low side going forward.

Halbach

&&

.LONG TERM...
Issued 257 AM CDT Fri Aug 15 2025

Saturday night through Thursday:

The active period of weather should continue Saturday night into
early next week, though the timing and placement of features each
day/night will depend on the previous day/night`s activity.

It appears that the quasi-stationary frontal boundary may sit
across southern Wisconsin or perhaps shift a little further south
Saturday night, with the boundary perhaps sliding south of the
area Sunday. The low level jet nose location is also uncertain,
and may remain over the area Saturday night into Sunday morning,
or focus more to the west. It appears that most of the organized
showers and storms would occur along and north of the stalled
frontal boundary, where the low level jet can interact with it.

For now, will maintain 20 to 50 percent PoPs until more certainty
is found with how things will evolve tonight into Saturday. Some
stronger storms are possible if organized storms can move through
the area.

The bigger concern will again be heavy rainfall, as bulk shear
vectors will be parallel to the front and low level jet nose
areas. Precipitable water values will be approaching or over 2.00
inches during this period, with warm cloud processes helping to
produce the heavy rainfall potential.

Subsequent rounds of showers and thunderstorms will continue to be
possible Sunday night into Tuesday or Tuesday night, as the low
level jet nose varies its position from over to west of the area.
Again, how things evolve will depend on what happens the previous
day/night periods. Heavy rainfall will remain possible during this
period with high precipitable water values and possible training
of showers and storms.

There is too much uncertainty to pin down anything definitive at
this point, so will maintain 20 to 40 percent PoPs for now.
Temperatures will remain uncertain as well, depending on the
frontal boundary location and clouds/precipitation. There may be a
break by Wednesday into Thursday, as high pressure may build into
the region from the north and northeast.

Wood


&&

.AVIATION...
Issued 257 AM CDT Fri Aug 15 2025

Expecting VFR conditions through Saturday except for when any
potential thunderstorms could come through. The main initial
chances for this appears to be across central Wisconsin late
Friday night into early Saturday morning. Brief periods of low
visibility and gusty winds are possible if these storms do
occur. A more active period of storms is expected to continue
through the weekend on into early next week.

Halbach

&&

.MARINE...
Issued 257 AM CDT Fri Aug 15 2025

Winds will gradually increase out of the south going into the
weekend as a ridge of high pressure drifts eastward towards New
England. The main concern across the lake will be with any lines
of storms that would bring a risk of high winds and waves along
with them. There appears to be multiple rounds of these types of
storms through the weekend on into early next week starting late
tonight into early Saturday morning. More northerly winds will
begin to settle in as the front sinks south and high pressure
pushes in from the north.

Halbach

&&

.HYDROLOGY...
Issued 257 AM CDT Fri Aug 15 2025

One Flood Warning and one Flood Watch remain in effect in the
Milwaukee metro area in the wake of the heavy rainfall this
past weekend.

The Lower Fox River at Waukesha remains in minor flood stage at
this time, but will continue to decrease in stage height. It
may remain in flood stage until early Saturday morning.

The Fox River at New Munster is forecast to reach minor flood
stage late Saturday or Saturday night, and is being monitored
with a Flood Watch.

Ponding of water in areas immediately near each river segment
will remain possible until each can fall below flood stage by
later this week. Continue to heed any road closures in all
impacted areas until river stages recede further and Flood
Warnings are allowed to expire.

There is potential for localized heavy rainfall again this
upcoming weekend, and area rivers (particularly in the Milwaukee
metro area and surrounding counties) will be monitored for
potential rises.

Halbach

&&

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

$$

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