NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 041113
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
613 AM CDT Tue Aug 4 2026

.KEY MESSAGES...

- Beach Hazards Statement in effect this afternoon and evening
  at Sheboygan County beaches. Stay out of the water and away
  from dangerous areas like piers and breakwalls!

- Periods of rain and storms expected starting this afternoon
  and continuing into Wednesday. Storms could produce heavy
  downpours. An isolated severe storm is possible Tuesday
  afternoon/evening.

- Heat & humidity return this weekend (highs in the mid 80s and
  heat index values in the low 90s).

- Storm chances return early next week (Sunday through Tuesday).


&&

.UPDATE...
Issued 612 AM CDT Tue Aug 4 2026

The forecast is on track for later today and tonight. An
approaching cold front that stretches from nw WI to nw IA
will continue to decay and slow as the attendant low pressure
area over Ontario moves farther away. The decaying front, and a
possible outflow boundary from the storms approaching the MS
River, will act as a focus for showers and storms this
afternoon over srn WI. The surface convergence will remain
rather weak, but PWATs are increasing to nearly 2 inches within
the 850 mb thermal ridge, and MLCAPE will rise to 1000J/KG.
Expecting the initial activitiy to be scattered but then
becoming more widespread through the night as broad and weak
upper troughing with 500 mb height falls of 30 m moves over the
region. A right entrance region of the upper jet will also aid
the overall lift. Thus believe the CAMs and deterministic models
for the widespread rainfall and one half to one inch amounts,
greatest toward the IL border.

Gehring

&&

.SHORT TERM...
Issued 115 AM CDT Tue Aug 4 2026

Today through Wednesday night:

Increasing cloud cover today ahead of a slow-moving cold front,
with highs in the low to mid-80s. Instability will increase
throughout the morning hours, with surface-based CAPE of 1000 to
1500 J/kg expected to build right ahead of the front during the
afternoon. Very low bulk shear and minimal shear in the
surface-850 mb level will prevent the majority of severe weather
from developing, but an isolated microburst or hailstorm cannot
be ruled out with plenty of moisture to work with (PWATs over
1.75 inch).

The front is expected to stall over southern Wisconsin overnight
tonight, with additional rounds of showers and isolated storms
possible throughout the overnight hours. Bulk shear increases to
near 50 kt overnight, but very little forcing outside of the
surface front as well as very low instability (~500 J/kg) will
prevent severe activity. However, high PWATs nearing 2 inches
may lead to localized flooding for regions that see multiple
rounds of rainfall.

Wednesday, low pressure ejects into central Illinois, bringing
additional potential for rain and storms within its northern
convergent band throughout the day. Some CAMs are indicating
potential for low pressure to lift into northern Illinois if
overnight convection clears early enough to destabilize in
southern Wisconsin. However, majority of modeling indicates a
more broad region of precipitation with CAPE around 500 J/kg and
PWATs remaining in the 1.75-2 inches range. Primary hazard
remains locally heavy rain.

Wednesday night, precipitation tapers off from northwest to
southeast as low pressure weakens and exits into Indiana. Expect
lows in the upper 50s to low 60s. Rainfall totals around an inch
are expected along and south of the I-94 corridor, with rainfall
totals below an inch north of I-94. Close to the WI/IL border,
up to 2 inches are possible (~15% chance). Locally higher totals
are possible within areas that see multiple rounds of storms.

MH

&&

.LONG TERM...
Issued 115 AM CDT Tue Aug 4 2026

Thursday through Tuesday:

High pressure returns on Thursday, with cloud cover slowly
exiting as low pressure continues to weaken to the southeast.
Expecting highs in the upper 70s to low 80s, with light and
variable winds. High pressure lingers through the overnight
hours, bringing lows in the upper 50s to low 60s.

Friday, winds will shift to southerly as high pressure
propagates eastward and low pressure propagates into the Hudson
Bay. Expect increasing temperatures and humidity, with highs in
the low 80s. Saturday, southerly winds continue, with highs in
the mid-80s. Isolated pop-up storms are possible as a weak
surface front moves through northern Wisconsin (~15% chances).

Saturday night into Sunday, low pressure in the northern Plains
will begin to bring frontogenesis/upper level ridging to the
western Great Lakes region, and a return to an active weather
pattern through early next week. Expect increasing heat and
humidity, with highs in the mid to upper 80s and heat index
values around 90 degrees. Multiple shortwaves riding over the
upper level ridging will serve as the basis for rain and storm
chances Sunday through Tuesday, with exact timing and therefore
intensity remaining uncertain at this time (30-50% PoPs
throughout the time period will be refined as individual
shortwaves become more clear later this week).

MH

&&

.AVIATION...
Issued 612 AM CDT Tue Aug 4 2026

VFR conditions today into the early evening, but scattered
showers and storms will begin to occur this afternoon and
evening. The showers and storms will become more widespread
through the night which will result in widespread MVFR and IFR
Cigs developing and lasting into Wed. Areas of 1-5SM BR and
light fog may occur toward sunrise Wed AM especially over south
central WI.


Gehring

&&

.MARINE...
Issued 115 AM CDT Tue Aug 4 2026

High pressure around 30.0 inches over the Great Lakes this
morning will gradually move southeastward throughout the day as
low pressure around 29.6 inches moves into the Hudson Bay,
bringing southwesterly winds to the Lake today. Gusts of 25-30
kt are expected across the northern two-thirds, with conditions
hazardous to small craft in portions of the nearshore regions
north of Port Washington this afternoon through this evening.
Winds will diminish and become generally light and northwesterly
tonight as a cold front from this low progresses southward
through the lake. Thunderstorms are expected along and ahead of
the front. Rain and storms remain possible through Wednesday
night as this front stalls. High pressure of 30.0 inches will
bring a return to light winds Thursday into Friday, with low
pressure developing again in northern Canada Friday into Friday
night, bringing a return to southerly winds and chances for
thunderstorms into the weekend.

MH

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052...2 PM Tuesday to 10 PM
     Tuesday.

LM...Small Craft Advisory...LMZ643...2 PM Tuesday to 10 PM Tuesday.

&&

$$

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