650
FXUS63 KMKX 191718
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1218 PM CDT Thu Sep 19 2024

.KEY MESSAGES...

- Showers and thunderstorms moving into south central WI this
  evening then weakening as it moves into SE WI late at night.

- More chances for showers and storms Sat nt into early next
  week.

- Cooler temperatures much closer to normal for next week.

&&

.UPDATE...
Issued 1217 PM CDT Thu Sep 19 2024

Showers and sct storms over ne IA are within an area of weak low
to mid level warm, moist advection and frontogenesis. Much of
this activity should dissipate as it approaches south central WI
this afternoon via low lvl dry air. Otherwise new convective
development is expected over se MN and far nrn IA late this
afternoon, as the trailing cold front to the occluded low over
Manitoba approaches the area. MLCAPE of 2500 J/KG are expected
ahead of the front with the front being aided aloft by the left
exit region of a 90 kt jet streak and PVA from a upper wave
passage. A sly LLJ and warm, moist advection will increase just
ahead of the front to 30-40 kts during this time.

The HREF produces a line of deep convection that will begin to
weaken after 03Z as it is moving across south central WI. This
seems reasonable as MUCAPE quickly drops after sunset with
perhaps 1000 J/KG over south central WI but much less to the
east. The better upper dynamics also track to the north during
this time. Nevertheless expect most locations to see measurable
rain tnt but probably fairly light for se WI. The actual cold
front will then pass for the morning daylight hours on Fri but
only with slight chances for development over ern WI. A drying
wly wind and clearing skies will still lead to another day with
high temps in the lower to middle 80s. Weak high pressure will
then follow for Fri nt with low temps falling back into the 50s.


Gehring

&&

.SHORT TERM...
Issued 230 AM CDT Thu Sep 19 2024

Today through Friday:

Another warm day expected today with mostly clear skies and
925mb temps in the 23-25 C range. This should bring temperatures
to the mid to upper 80s for much of the CWA with cooler
temperatures near the lake from the expected development of the
lake breeze.

As we move through the afternoon and especially into the evening
hours we will see showers/storms pushing in the from the west as
a front pushes in with some PVA aloft helping out. The midlevel
moisture and WAA will be sufficient as well in allowing for the
potential for storms to push into the area. There is some
uncertainty on how early storms might push in but we could see
NW parts of the CWA get clipped by some storms in the afternoon.
However most of the potential convection is expected into the
early to late evening hours. While shear will certainly be
sufficient (30-40kts) for severe storms the timing of storms
being more in the evening suggests we will quickly lose much of
our instability in the evening hours. Thus we could expect some
stronger storms to the west, perhaps even some borderline severe
storms but as they slide east they will weaken as we move later
into the evening.

Generally CAMs suggest organized storm activity through the
evening and overnight period but they do not show much in the
way of stronger storms by the time they push into the western
parts of the CWA. Regardless we will watch for potentially
strong storms tonight.

Into Friday, models suggest the storms and remaining showers
will have pushed out of the CWA off to the east though still
awaiting the passage of the front which is estimated to come
through some time after sunrise Friday morning. The rest of the
day Friday looks relatively quiet with clearing skies from the
west through the day. Temperatures behind the front will be
cooler with highs only expected to reach the low to mid 80s

Kuroski

&&

.LONG TERM...
Issued 230 AM CDT Thu Sep 19 2024

Friday night through Wednesday:

Quieter conditions are expected to continue Friday night through
much of Saturday as another brief period of ridging pushes back
in with weak high pressure over the area. While some models
suggest an earlier arrival in the next system (GEFS), most
models suggest that much of Saturday will remain dry with the
next system not impacting the region until at least Saturday
night into Sunday.

This system will be fairly drawn out over the course of a few
days with an upper level closed low gradually migrating east
northeast from the southwest US on Saturday to the Central
Plains by Sunday. However the impacts of this system will be
felt further away as the closed low will feature a `wing` of PVA
extending eastward toward the CWA. This, in addition to broad
developing surface low pressure with some moisture available in
the mid levels as well as some WAA may lead to precipitation
starting as early as Saturday night with ongoing chances through
at least Monday night before the surface low pulls through.
Precip chances may linger into Tuesday on the backside of the
low before we finally see a return to drier conditions.

This system will bring us back to near average temperatures with
Sunday featuring the front coming through with broadly high
pressure conditions returning by Tuesday with highs the rest of
the week likely to be in the low 70s. Plenty of uncertainty with
precip chances beyond Tuesday. Some models suggest weak chances
for the middle of next week but by the end of the week stronger
high pressure should be building into the region in some form.

Kuroski

&&

.AVIATION...
Issued 1217 PM CDT Thu Sep 19 2024

VFR conditions this afternoon into the early evening. Areas of
MVFR Cigs may then develop over south central WI late tnt
following the showers and storms. Also cannot rule out patchy
fog toward morning west of Madison and especially in the WI
River Valley. Any pockets of MVFR Cigs and light fog will burn
off within a few hours of sunrise on Fri with VFR conditions by
late morning through the afternoon.


Gehring

&&

.MARINE...
Issued 1217 PM CDT Thu Sep 19 2024

High pressure around 30.0 inches over the lower Great Lakes today
will gradually weaken, while low pressure around 29.4 inches
tracks northeast across Manitoba, Canada. This will produce light
to modest south to southeast winds into Friday. A weak cool front
will push southeastward across the open waters Friday evening,
bringing scattered showers and isolated thunderstorms from late
tonight into Friday evening.

Weak high pressure will then settle over the lake for Saturday
morning, followed by the passage of a weak wave of low pressure
around 29.7 inches for late Saturday night and Sunday. Light to
modest southeasterly winds can be expected ahead of this low.

Gehring

&&

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

$$

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