186
FXUS63 KMKX 130333 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1033 PM CDT Wed Jun 12 2024

.KEY MESSAGES...

- A round of showers and storms may push in overnight along and
  ahead of a cold front with additional chances Thursday
  afternoon closer to the WI/IL. While cannot rule out a
  stronger storm or two, the better severe chances look to be
  south in IL.

- Brief cool down Friday and Saturday, but hotter temps build in
  for Sunday into early next week.

&&

.UPDATE...
Issued 1032 PM CDT Wed Jun 12 2024

Storms diminished quickly after they entered our forecast area
this evening. The gust front packed a punch almost all the way
to Milwaukee, with gusts up to 40 mph.

The next round of storms is just north of the Twin Cities,
through northern WI, and into the U.P. These are just ahead of a
cold front. Those storms will have a weakening trend overnight
as they track east-southeast, and should track through southern
WI between 3 and 7 AM.

The small-scale models have a handle on the current convection,
but all have different ideas about the track and intensity
overnight. The 00z NAMNest, HiResWRF and HRRR models are showing
reasonable solutions. They have the northern WI convection
weakening but making it into central WI from Marquette to
Sheboygan Counties. They also develop some weak storms over
northeast IA along the nose of a low level jet after midnight
and then have them drift into south central WI early in the
morning while weakening.

The CAPE of around 1000 j/kg and bulk shear just over 40 kt is
on the high side over southern WI overnight, so storms moving
into the area should be able to be sustained, but models insist
on diminishing it over us. The reason may be that the LLJ will
be veering with time, and the low level stability will be
increasing as the convection runs out farther ahead of the
synoptic forcing along the cold front.

The actual cold front should stall somewhere in central WI
tonight and then drop through southern WI during the afternoon.
This is farther north than the previous model runs were showing. The
moist and unstable air mass over us can support storms along
this cold front, and severe could be possible depending on the
timing of that front slipping southward. SPC may need to nudge
the Slight Risk northward into the southern tier of counties in
WI to capture some of the earlier storms before they really
gather strength across IA and IL.

Cronce

&&

.SHORT TERM...
Issued 347 PM CDT Wed Jun 12 2024

Tonight through Thursday night:

Continue to watch the showers/storms that have now pushes into west-
central WI. This activity is battling the dry air ahead of it and
the latest radar imagery shows this trend. However, think there is a
large enough area of showers to overcome the dry air and saturate
enough to sneak a few scattered showers and a storm or two into the
western half of our CWA this afternoon/early evening, especially for
areas along and west I-39 corridor. Otherwise, expect the
better development of this activity to stay to our west-
southwest along the effective warm front and where the higher
moisture remains, which looks to clip areas southwest of
Madison. This activity looks to decay the further east it makes
it, especially given the outflow outrunning it. The latest 18z
HRRR is pinging that a few additional showers and storms may
develop ahead of the activity along this outflow this evening
and if a storm or two does end up initiating along the outflow,
then you cannot rule out an elevated hail threat and some gusty
winds mixing down to the surface, especially given the
inverted-V feature on this afternoon`s model soundings. However,
still think it is underestimating the dry air mass ahead and do
not foresee the dewpoints climbing as high nor as widespread as
it progs enough to support much of any significant development
across southern WI as dynamics remain to the southwest. But
will bear watching.

After this late afternoon/early evening round, will then see a lull
in rainfall chances later this evening before picking back up
overnight into early Thursday morning with any anticipated activity
that develops upstream through the evening to the northwest. Given
timing and slightly better moisture, this may be the round to see
better rainfall as the cold front gradually slides through from
the north-northwest. Again the overnight timing may limit
activity, but cannot ruled this line maintaining itself enough
to sneak into our east-central counties through the morning
hours.

The third window to keep an eye on will be Thursday afternoon as the
cold front and main forcing mechanisms for triggering storms pushes
through southern WI. Timing of the boundary will be important
for any storm development, which at this time looks to mainly
push south into IA/IL before initiating storms Thursday
afternoon/evening. However cannot rule out a stronger storm or
two to develop on the north side of the WI/IL border, especially
if the cold front ends up slowing down. The environment will be
primed for if a storm does develop in the hot and humid
airmass, it can grow upscale quickly given large MUCAPE building
to around 2000 J/kg and modest deep layer (0-6km) shear around
35-40 kt ahead of the frontal boundary. Main thinking is the
cold front will push south of the Cheddar Curtain by Thursday
afternoon and the better strong to severe thunderstorm chances
will be across IA/IL. On the other hand, if the front ends up
slowing down, then we could see the more favorable environment
follow suite, which could bring the severe threat into our
southern tier of the CWA.

Otherwise, expect another day of very warm temps and muggy
conditions for Thursday with highs in the mid to upper 80s,
until the cold front pushes through. Then will see drier airmass
and cooler temps settle in Thursday night with high pressure
approaching the area.

Wagner

&&

.LONG TERM...
Issued 347 PM CDT Wed Jun 12 2024

Friday through Wednesday:

Ridging and high pressure will begin to build into the Midwest
from the Northern Plains Friday. Cooler temperatures are expected
Friday with high temperatures in the mid 70s to low 80s. Northerly
winds and some very weak caa will be the contributing factor to
this especially with the cold front that moved through the day
prior. High pressure is expected to be overhead of the state on
Saturday. Southeast winds will set up Saturday afternoon and
evening as the high pressure center moves east of the state. This
will kick off a warming trend. The focused WAA will bring a small
chance for some showers and thunderstorms to develop, but chances
will be low around 20%.

Sunday, the state will be on the fringe of a synoptic scale
trough that will be advancing northeast from the northern plains
towards James Bay. Under the very warm and humid conditions that
are expected, any vertical lift present will be able to produce
some rain and a few storms. The best support for any rain activity
will be to the north of our forecast area. Overall this has
resulted in some low chance POPs (20-35%) throughout the day
Sunday into Monday. The low chance POPs of 20% or less will
persist through the rest of the extended forecast (Tuesday and
Wednesday). The strong ridging that sets up in the extended over
the eastern CONUS and troughing to the west, puts Wisconsin on
that transition line between these two features. However, the
500mb jet looks to remain north of the state. This would likely
keep the best chances for rain/storms to our north, but not all
extended guidance is on the same page. The Canadian for example
does break down the western extent of the ridging a bit more and
has an incoming trough dig a bit further south. Due to this
uncertainty, this is were the low chance POPs are coming from.

Sunday through the rest of the extended will be hot and humid
across southern Wisconsin with dewpoints pushing into the 60s to
70s. This pattern has been very consistent over the last couple of
days. What this means is temperatures in the 80s to 90s and heat
indices potentially in the 90s for a couple days in a row.

Patterson

&&

.AVIATION...
Issued 1032 PM CDT Wed Jun 12 2024

Another round of showers and storms are possible overnight
between 09z-12z. These would be from decaying storms in northern
WI and perhaps northeast IA. Model trends continue to favor
weakening/decaying storms, which could bring lower flight
conditions briefly. A cold front will drop down through southern
WI Thursday and there may be another round of showers and
storms, mainly for areas south of I-94 and closer to the WI/IL.

Cronce

&&

.MARINE...
Issued 347 PM CDT Wed Jun 12 2024

Southerly winds will continue across the lake through the
evening, but expect it to increase and turn more west-
southwesterly overnight ahead of an approaching cold front. May
see a few showers and storms with the cold front. Then expect the
front to push across Lake Michigan through the day Thursday with
winds turning more to the northwest behind it later in the day
Thursday. Northerly winds will persist into Friday, but gradually
weaken as high pressure builds across the region through the
end of the week. Then as the high pushes out of the region,
expect winds to turn more southerly and increase through early
next week as a very warm and humid airmass pushes into the
region.

Wagner

&&

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

$$

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