NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 031125 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
625 AM CDT Fri Jul 3 2026

.KEY MESSAGES...

- Chances (about 30 to 50 percent) for thunderstorms this
  afternoon and evening (around 12 PM to 8 PM) if enough
  instability recovery occurs in the wake of morning
  showers/storms. A few severe storms with strong winds and
  hail are possible. Keep up with the forecast if planning to be
  outdoors.

- Additional batches of showers and storms continue late
  tonight through Sunday. Keep up with the forecast if planning
  to be outdoors.

- Trending quieter early next week.

&&

.UPDATE...
Issued 625 AM CDT Fri Jul 3 2026

There is ongoing convection over central and northern IL, with
the stratiform region extending all the way through southern MN.
Light rain is starting to spread into southwest WI. With
southern WI and northern IL being quite worked over from last
night (currently low CAPE and high CIN per mesoanalysis), the
chance for storms from the Iowa complex making it into here is
quite low. We have low chances (20 to 40 percent) west of
Madison this morning, but much lower east. Any robust convection
that is triggered from outflow from that complex would favor a
track into northern IL, where the previous remnant outflow
boundary lies.

The main question is what will happen to the IA complex over
the next few hours. Many of the meso models seem to have a
decent handle on it right now, make sense with the overall
environment, and agree that the current storm complex should
diminish while they are still in IA (probably over northeast
IA). With how organized it is looking on satellite, there is a
real probability that an MCV (mesoscale convective vortex) could
stem from this and track northeastward through southern WI this
afternoon with the 700-500mb steering flow.

With the likelihood of sunshine over most of southern WI by
late morning, our instability should recover to over 1500 J/kg
of CAPE. An MCV would create localized shear and a trigger
mechanism for scattered storms. Therefore, we kept mid-late
afternoon chances (30 to 50 percent) of storms over southern WI
in the forecast. Parameters would support a localized severe
threat with damaging winds the main concern. Timing-wise, the
MCV should be able to move out of east central WI by mid-evening
and thus diminish our storm chances.

There is still a lot of uncertainty with this type of weather
pattern and the scenario could change, so keep up with the
forecast.

With the IA storm complex taking its time making it into
southwest WI, we did not see a need to keep the Flood Watch for
Sauk County going all the way until 7 AM, so we canceled it
early.

Cronce

&&

.SHORT TERM...
Issued 200 AM CDT Fri Jul 3 2026

Today through Tonight:

Synopsis/Mesoanalysis: Regional radar mosaics remain busy
tonight following an evening of strong to severe storms across
southern Wisconsin. Said storms laid down an elongated outflow
boundary, which currently stretches from the Chicago metro to
just south of the Des Moines, Iowa vicinity. Thanks to a
southwesterly low level jet in place regionally, ascent up &
over the outflow has allowed convection to blossom to the
north/cool side of the boundary from Iowa across northern
Illinois. Some of this activity could leak north into southern
Wisconsin through the remainder of the overnight hours,
particularly to the south of I-94 and US-18. Further to the west
over the Central Plains, additional widespread convection is
ongoing over Nebraska. While these storms will remain well west
of the area through tonight, high-res forecast guidance is
hinting at an affiliated remnant shortwave/MCV crossing the
region this afternoon. Whether this feature will be able to
trigger storm development will depend on air mass recovery in
the wake of predawn showers/storms regionally, with forecast
trends being monitored through the rest of this morning. In the
event storms were to form this afternoon, a few would be capable
of producing gusty straight line winds. Additional showers and
storms are possible during the predawn hours Saturday. With
clouds & areas of showers/storms around the region, temperatures
are expected to remain below heat headline thresholds today.

Rest of the Overnight: Will be monitoring convective trends
over Iowa and northern Illinois as storms regenerate over the
top of outflow boundaries laid down by earlier evening
convection. Expect that development will continue over these
regions through the remainder of the overnight hours given a
persistent southwesterly low level jet & attendant overrunning.
Whether activity manages to propagate further north/into
southern Wisconsin remains more uncertain, as the low level air
mass remains worked over in the wake of multiple batches of
convection last evening. Best convective potential will be
along/south of I-94 & US-18, where elevated instability values
remain a touch higher compared to further north. Not expecting
severe weather in the event convection makes it back into the
area, though heavy downpours would be possible. Have maintained
the existing Flood Watch over Sauk Co given antecedent wet
conditions & convective chances. If appreciable precip stays
south of the region through the rest of the overnight, watch
will be allowed to expire as scheduled at 7 AM.

This Afternoon & Evening: Forecast uncertainty increases as a
remnant shortwave/MCV from storms currently over the Missouri
Basin moves across the region. If sufficient destabilization can
occur in advance of the feature, it could help trigger
scattered storm development during the ~12-8 PM timeframe, with
a few severe storms with gusty winds and hail possible. If,
however, morning convection over Iowa/Illinois/southern
Wisconsin holds better instability to the south of the region,
storm coverage would be minimal. Will thus be monitoring trends
closely, as what storms do through the morning hours will go a
long way in determining what the radar looks like come
afternoon. Will continue to provide forecast updates through the
morning.

Tonight: Will be watching for more thunderstorms during the
predawn hours as one or multiple clusters of convection move
into the Mississippi Valley from the Plains. Expect that
convective intensities will be waning as these storms approach,
likely limiting severe potential. Will continue to monitor
trends and provide updates through today.

Quigley

&&

.LONG TERM...
Issued 200 AM CDT Fri Jul 3 2026

Independence Day through Wednesday:

The upper ridge over the eastern CONUS will gradually diminish
as mid level westerlies win out as they head east of the Great
Lakes region Sunday and Monday. Unfortunately, our region will
remain in a battle zone of sorts for Independence Day into
Sunday. From a large scale pattern perspective, it is prudent to
expect an convective system or two. However the timing and
details will be heavily determined by how the mesoscale is
altered by convective behavior and remnant boundaries Friday and
Friday night. At this time, from a large scale pattern
perspective, it appears the better rain chances shift east of
the area on Sunday, but this will have to be closely monitored
day to day.

Early next week, ensemble consensus is for a mid level ridge to
build over the Rockies, nudging our upper level pattern into
northwest flow. This will deliver typical July conditions with
lows in the 60s and highs in the 80s. Small ripples from time to
time are to be expected in this northwest flow pattern, though
timing these individual waves is a futile exercise. Bottom line,
there will be a good amount of dry time, and intermittent
chances for showers/storms with any ripples.

Gagan

&&

.AVIATION...
Issued 625 AM CDT Fri Jul 3 2026

Current area of showers and storms west of the area should have
a tough time holding together as it tries to shift east into
the morning hours. May see a few showers or storms make it to
Madison or Janesville terminals later this morning or midday,
before weakening. Otherwise, middle level clouds may be
scattered to broken at times today, depending on how long the
precipitation to the west keeps going. Winds should remain
fairly light today into tonight.

This will help determine if more showers and storms develop
this afternoon and early evening across the area. There is a
decent amount of uncertainty on timing and areal coverage of any
showers or storms, so kept PROB03 mentions going in the TAFs
for all terminals this afternoon into early evening. Stronger
storms could bring strong winds and hail.

There may be more chances for showers and storms at times
tonight, with the better chances toward the Illinois border.
Again, kept PROB30 mentions going in TAFs, though Janesville and
Kenosha may see prevailing showers or storms after midnight
tonight.

Wood

&&

.MARINE...
Issued 200 AM CDT Fri Jul 3 2026

High pressure around 1020 mb will remain parked over the Ohio
Valley and Appalachian Mountains into tonight. Meanwhile, a
trough of low pressure will remain over the Great Plains through
tonight. A weak low pressure area may then organize and slowly
move across Wisconsin and Lake Michigan from Saturday afternoon
into Sunday, or pass farther south across Illinois into the Ohio
Valley. Modest south to southwest winds will become lighter
today. Light to modest winds are then forecast for the weekend,
but with some uncertainty on wind direction given low confidence
in the track of the low. A stormy period is expected for
central and southern Lake Michigan through the weekend. Patchy
marine fog will be possible at times as warm and humid air flows
over the relatively cooler lake.

Quigley

&&

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

$$

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