755 
FXUS63 KMKX 201809
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
109 PM CDT Thu Aug 20 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms (30 to 60 percent chances)
  with passing cold front mainly Friday afternoon and evening.
  Gusty winds and small hail may occur.

- Small chances (20 to 30 percent) for a shower or storm 
  Saturday afternoon for portions of east central and southeast 
  Wisconsin.

&&

.SHORT TERM...
Issued 109 PM CDT Thu Aug 20 2026

Tonight through Saturday:

Some modest warm air and moisture advection should move into 
the area tonight into Friday, which should support some showers 
and a few storms northwest of Madison later tonight. 

The cold front will then move southeast into the area Friday,
then exit to the southeast by later Friday night. There is not
much middle to upper level support to go with the front and 
modest warm air/moisture advection. Recent CAM runs have been 
producing more showers and storms along and ahead of the front 
during the afternoon and early evening with peak heating, 
especially in eastern portions of the area. 

Thus, brought up precipitation chances in to the 50 to 60-plus 
percent range in the late afternoon and early evening. Forecast 
soundings are showing mean layer CAPE of 1200 to 1500-plus J/kg,
with 20 to 25 knots of deep layer bulk shear. This may support 
gusty winds and small hail with any stronger storms during this 
period. 

There may be a shower or storm (20 to 30 percent chances) that 
occurs Saturday afternoon for portions of east central and 
southeast Wisconsin, with a weak surface low/convergence from 
lake breeze shifting southward near the western shore of Lake 
Michigan. There is some differential CVA that may move through 
with a broad 500 mb trough digging through the region. 
Confidence is low with the areal coverage of any precipitation 
Saturday, as upward vertical motion is modest at best. Forecast 
soundings do support a shower or storm if something can develop.

Temperatures look to remain near seasonal normal values into
Saturday.

Wood

&&

.LONG TERM...
Issued 109 PM CDT Thu Aug 20 2026

Saturday night through Thursday:

Shower and storm potential is expected to decrease Saturday 
night. Sunday and Monday highlight a high pressure system and a 
strengthening upper level ridge, which should keep the region 
drier with high temperatures in the middle to upper 70s.

The next chance for showers and storms suggests to be late 
Tuesday afternoon through the evening, potentially into early 
Wednesday (40 to 50 percent), as a low pushes down over the 
Great Lakes region from northern Minnesota and Canada. The bulk 
shear of around 40 to 50 knots could bring a severe risk with 
these storms, but the timing and severe risk remains uncertain. 
The south central region is expected to become drier through 
Wednesday, with a continued potential for precipitation near the
lake through the afternoon as the low moves east.

Wednesday night and into Thursday show generally drier and fair
conditions to return, as high pressure and a shortwave ridge 
build in.

Zawlocki

&&

.AVIATION...
Issued 109 PM CDT Thu Aug 20 2026

Scattered to perhaps broken diurnal cumulus around 5000 feet 
AGL should continue until early this evening. More ceilings from
the northwest should move into the area by later tonight into
Friday, gradually lowering to around 5000 feet AGL. 

A cold front will move southeast into the area Friday morning 
and exit by later Friday night. Some showers and a few storms
may move into areas northwest of Madison later tonight, with
scattered showers and thunderstorms Friday into Friday evening.
Better chances for Friday afternoon and early evening. Gusty
winds and small hail may occur with any stronger storms. Locally
lower ceilings and visibility values would accompany any storms.

Light and variable winds, with the east to southeast lake breeze
for terminals near the lake, are expected into early evening.
These winds will become south tonight and southwest on Friday. 
They will shift northwest by later Friday night.

Wood

&&

.MARINE...
Issued 109 PM CDT Thu Aug 20 2026

Light to modest winds are expected into this evening, as high 
pressure around 30.0 inches tracks through the western Great 
Lakes region. As the high pressure exits to the southeast later 
tonight, south to southwest winds will develop. Theses winds 
will increase for Friday, along with shower and thunderstorm 
chances, as low pressure around 29.8 inches moves across the 
region and drags a cold front through Lake Michigan. 

Gusty winds will then shift to the northwest later Friday night
into Saturday after the front exits. Another high pressure 
system around 30.2 inches is expected to build into the region 
later this weekend, which may maintain gusty northerly winds as 
it moves in.

Winds may get close to Small Craft Advisory levels Friday 
afternoon north of Port Washington, though it may only be for a 
short period of time.

Wood

&&

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

$$

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