938
FXUS63 KMKX 231842
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
142 PM CDT Mon Sep 23 2024

.KEY MESSAGES...

- Showers for se WI on Tue with at least a small potential for
  heavy rainfall rates over far se WI.

- Mild and Dry conditions for Wed-Fri.


&&

.UPDATE...
Issued 142 PM CDT Mon Sep 23 2024

Middle to high clouds will increase from the south late this
afternoon into the evening as a shortwave trough over srn IA
lifts nwd through srn WI. High based elevated instability may
lead to some virga or even sprinkles this evening. Farther to
the west a 110 kt nly jet streak will dig a shortwave trough
from the nrn Great Plains to the IA/MO border by 00Z Wed. This
will kick the shortwave trough over KS and weak low over srn MO
newd on Tue. There are differences on the track of the low but
the main positioning would take the low and upper wave across
nrn IN into south central lower MI. This would bring PWs over an
inch into far se WI with near saturation up to 10-15 kft
possible. Frontogenesis in the sfc-850 mb layer cloud trigger
some narrow bands of mdt to even heavy rainfall, but overall
confidence is low in actual occurrence. A farther srn track like
the NAM would greatly limit rainfall coverage while a more nrn
track like the ECMWF would bring higher confidence for heavy
rainfall rates in se WI. At this time will forecast 60-70
percent chances for showers from MKE south to ENW with smaller
probs for heavy rainfall rates. The showers may then linger
into Tue nt over far se WI.


Gehring

&&

.SHORT TERM...
Issued 410 AM CDT Mon Sep 23 2024

Today and Tonight:

Cooler temperatures, drier air and mostly clear skies are in
store for much of southern Wisconsin today. With the cold front
to our east in Michigan and Indiana, a drier air mass will move
into the state bringing dewpoint temperatures in to the mid 40s
to low 50s. With the light winds away from lake Michigan and the
clear skies, there is a small chance for some fog to develop
early this morning prior to sunrise. The best chances for fog to
develop will be in the northwestern corner of our forecast area,
particularly in the low lying areas. The window for this fog to
develop will be small as were looking for the dew point
depression to be at or near zero before the drier air mass
begins to move in.

Outside of this, the beach hazard statement and high swim risk
remains in effect for southern Wisconsin beaches through this
afternoon (into this evening for far southeastern Wisconsin).
This is due to the north to northeast gusty winds and building
waves. The tighter pressure gradient over the Lake will
eventually shift and weaken, which will cause the waves to
diminish later today.

The chance for rain returns to southern and eastern Wisconsin
tonight into Tuesday. A low pressure system will move from the
mid Mississippi valley and is expected to pass near the southern
portion of Lake Michigan. There is still a bit of uncertainty on
the track of this low pressure system. The difference in track
is how far to the south will this low pass. Keep POP chances low
with the with 40% chance being the max across far southeastern
Wisconsin during the early morning hours Tuesday. There will be
a brief period of east winds expected, which should help with
some moisture advection that wraps around the low. Otherwise the
better chances for rain and thunderstorms is expected to stay
to the south.

Patterson

&&

.LONG TERM...
Issued 410 AM CDT Mon Sep 23 2024

Tuesday through Sunday:

As the low pressure system moves out of the southern Great Lakes
Region, guidance has it interacting with a Canadian surface
high. This would likely slow down the forward progression of the
low pressure system causing it to linger a bit over Lake
Michigan and far eastern Wisconsin. So low chance POPs around
15% are expected to persist into Tuesday evening. After this low
pressure system exits, the Rex Blocking Pattern is expected to
set up across the Central CONUS. This pattern will then dominate
through much of the week. This pattern would keep Wisconsin dry
and slightly warmer with highs slightly above normal in the mid
to upper 70s.

Uncertainty returns for the weekend as long term guidance
suggests a tropical system advecting northward out of the gulf
and interacting with the center low pressure system of the Rex
Blocking Pattern. If these two low pressure systems due
interact, its likely that the Fujiwara effect would take over
and cause them to rotate around the center point (kind of looks
likes its rotating around each other for those who are less
familiar with this effect). This brings in a lot of uncertainty
on the track and how this would break down the blocking
pattern. Especially when the strength of the system coming out
of the gulf would be a key factor. Kept to the average among
guidance which introduces some low chance POPs around 30% or
less for the weekend.

Patterson

&&

.AVIATION...
Issued 142 PM CDT Mon Sep 23 2024

Sct-bkn035 cumulus this afternoon then lingering over far ern WI
into the evening. Patchy fog will develop in low lying areas of
south central WI late tnt. Farther east, MVFR Cigs will move
from Lake MI well inland during the early morning hours of Tue
and remain over ern WI throughout the day. Areas of Cigs below 1
kft and vsbys of 2-5SM BR are expected especially near the
lake. The intermittent showers will contribute to the reduced
vsbys at times.

Gehring

&&

.MARINE...
Issued 142 PM CDT Mon Sep 23 2024

Modest north to northeast winds will persist through this
afternoon as low pressure around 29.9 inches over the lower Great
Lakes continues toward the New England States. Meanwhile high
pressure around 30.1 inches over Lake Superior and northern WI
will move just slightly eastward. Low pressure around 29.7 inches
then track from southern IL to southern lower MI on Tuesday while
surface ridging remains over Lake Superior. This will maintain
modest east to northeast winds to the lake. The winds will then
shift northerly for Tuesday night and Wednesday as the low moves
away. A Small Craft Advisory will expire this afternoon as winds
and waves continue to subside.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ071-WIZ072 until 4 PM
     Monday.
LM...Small Craft Advisory...LMZ645-LMZ646 until 4 PM Monday.

&&

$$

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