-- Discussion containing changed information from previous version are highlighted. --
607
FXUS63 KMKX 200300
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1000 PM CDT Wed Jun 19 2024

.KEY MESSAGES...

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- On and off thunderstorm chances will continue into this
  weekend.

- Areas of fog (some dense) may develop over Lake Michigan
  tonight, and could drift into lakeshore counties tonight into
  Thursday AM. Patchy fog is possible further inland.

- A break from the heat on Thursday, but heat index values will
  be back in the middle 90s Friday and Saturday.

- A moderate swim risk is forecast Thursday morning at Sheboygan
  County beaches. Low swim risk for the afternoon and onwards.
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&&

.UPDATE...
-- Changed Discussion --
Issued 1000 PM CDT Wed Jun 19 2024

The effective front created by storm outflow has finished
crossing the region, leaving the CWA in a weak northerly flow
regime. Additional rounds of showers and weak thunderstorms are
possible tonight (50% rain chance). Additional RH from
overnight rainfall and / or radiational cooling through breaks
in the clouds may lead to patchy fog development in our CWA
overnight, dissipating a few hours after sunrise. Areas of fog
(with patches of dense fog possible) could develop more easily
over the cool waters of Lake Michigan, with northeast winds
possibly advecting it into lakeshore counties Thursday AM.

Lake Michigan wave height forecasts have trended lower, but the
northeast winds and building waves Thursday morning are still
expected to create Moderate Swim Risk conditions for Sheboygan
county beaches. Wave heights decrease in the afternoon.

Sheppard
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&&

.SHORT TERM...
Issued 310 PM CDT Wed Jun 19 2024

Tonight through Thursday night:

Cold front will continue to shift southeast through the area and
into northern Illinois into this evening. Scattered showers and
storms continue to develop and slowly shift northeast through
parts of the area, both near the front and where convective
temperatures may be reached. CAMs continue to support the
scattered showers and storms into early this evening across the
area.

The best instability will be toward southeast Wisconsin, where
mean layer CAPE up to 1500 J/kg or so is expected, perhaps
higher in spots. Areas further northwest may have more clouds
move in with the front, so mean layer CAPE there will be lower.
0 to 6 km bulk shear values should increase by early evening
into the 20 to 25 knot range, though the southeast parts of the
area will be on the lower end of this range.

This would mean short-lived airmass thunderstorms that have
some downburst wind potential, as forecast soundings are showing
some inverted V structures to them in the low levels. In
addition, cannot totally rule out a landspout spinup, as 0 to 3
km CAPE values are above 100 J/kg along the front and are
coinciding with some surface vorticity with the front. The
probability is low, but not zero. We will keep an eye on this.

Heat index values in the lower to middle 90s are expected to
linger in southeast Wisconsin until early this evening. Cooler
but still mild temperatures are expected later tonight into
Thursday, as winds shift northeast and lower clouds move in.
Some fog and low stratus clouds may also push onshore near the
lake overnight into Thursday morning. The clouds may linger for
a good part of Thursday.

Chances for showers and storms will continue at times overnight
into Thursday night, as some modest 850 mb warm air advection
and convergence/frontogenesis response lingers near the area.
Areas near the Illinois border may see the best chances for
storms Thursday afternoon and evening, as some better low level
frontogenesis with the front just to the south of the area
interacts with warm and unstable air. May see some gusty winds
with any of those storms as well.

&&

.LONG TERM...
Issued 310 PM CDT Wed Jun 19 2024

Friday through Wednesday:

Models are generally showing the warm front shifting north
across the area Friday into Friday night, before moving further
north for Saturday. Chances for showers and storms will remain
during this period. The area should get into the warm sector and
become very warm and humid again on Saturday with southwest
winds. A cold front looks to shift east across the region
Saturday night, bringing another chance for showers and
thunderstorms. Will have to watch this period for stronger
storms, though deep layer bulk shear values are only 20 to 25
knots at this time.

There may be a lull in precipitation chances Sunday into Monday,
as high pressure may move through the region. Temperatures look
to remain near to above normal into next week per ensemble
trends. Chances for showers and storms may return for the middle
of next week as well, as ensembles are showing a generally wet
Tuesday into Wednesday period.

Wood

&&

.AVIATION...
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Issued 1000 PM CDT Wed Jun 19 2024

Light north to northeast winds expected overnight. Patchy fog is
possible for all areas, with the potential for areas of fog
(some dense) over the southern half of Lake Michigan. Lakeshore
county airports may see this denser marine fog and/or IFR
stratus cloud ceilings drift inland due to the northeasterly
wind. Though inland airports are farther from this marine layer,
a west-to-east arrival of additional showers and weak
thunderstorms overnight is likely to lower cloud ceilings to
MVFR, with IFR possible.

Off and on shower / thunderstorm chances continue into Thursday
and this weekend. Cloud ceilings gradually improve throughout
Thursday.

Sheppard
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&&

.MARINE...
Issued 310 PM CDT Wed Jun 19 2024

A cold front will gradually sink southeast across Lake Michigan
into tonight. South to southwest winds will shift northwest to
north this evening, and northeast to north later tonight into
Thursday. Patchy to areas of marine fog may form tonight and
linger into Thursday morning, with some dense fog possible.

North to northeast winds should then linger into Friday, as high
pressure around 30.4 inches moves from Lake Superior into Ontario.
Gusty south to southwest winds are then anticipated to return for
Saturday into Saturday night, as low pressure around 29.5 inches
shifts into the region.

Wood

&&

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

$$

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