103
FXUS63 KMKX 171938
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
238 PM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Summer-like warmth continues through the remainder of the week.
  Daytime highs will range between five and fifteen degrees
  above normal.

- Dry conditions prevail through Thursday, then a cold front
  brings showers and storm potential Thursday night and Friday.
  On and off chances for showers and storms are then expected
  Saturday into Monday.


&&

.SHORT TERM...
Issued 238 PM CDT Tue Sep 17 2024

Tonight through Wednesday night:

Dry and hot conditions continue through today and Wednesday with
high temperatures in the mid to upper 80s away from the immediate
lakeshore. Low dewpoints will lead to relative humidity values
falling into the 25 to 30 percent range both today and Wednesday
away from Lake Michigan. A few spots in southwestern Wisconsin may
dip below 25 percent at times. A lake breeze will keep
temperatures and humidity values temperate in the afternoon hours
in Lake Michigan counties both days. Relief from the heat is
expected during the overnight hours tonight and again Wednesday
as low dewpoints continue and a lack of cloud cover allow
temperatures to fall into the mid-50s.

High pressure dominates to the east, while semi-permanent low
pressure lingers in the northern High Plains. This will yield
light southeasterly winds through Wednesday, except for nearly
calm winds during the overnight hours. Areas along the Kettle
Moraine and low-lying river valleys are expected to see patchy
ground fog development once again.

MH

&&

.LONG TERM...
Issued 238 PM CDT Tue Sep 17 2024

Thursday through Tuesday:

Blocking pattern begins to erode with an upper-level cutoff low
pivoting into the Desert Southwest on Thursday, with a jet
streak riding over the Great Plains Ridge and assisting with
frontogenesis across the Upper Midwest. This frontal development
will progress eastward slowly Thursday evening into Friday, but
the overall pattern looks to pull the surface low northward,
limiting the cooling and moistening effects of this front.
Still, showers and thunderstorms are possible Thursday night
into Friday along this frontal boundary, especially in
southwestern Wisconsin. Meanwhile, an additional upper level
trough feature pushes into western Canada, with interplay
between this trough and the Desert Southwest cutoff setting the
stage for precipitation this weekend into early next week.
Surface high pressure is expected to slowly shift northward
between developing low pressure in the lee of the Rockies and a
developing low in the Atlantic. Phasing between the Canadian and
Southwestern troughs will dictate the strength of the western
low pressure system and therefore when and how much
precipitation southern Wisconsin will see Sunday through early
next week. Confidence remains low, with models diverging widely
as per placement and timing of troughing, so generally kept NBM
PoPs through the weekend into early next week (20 to 40 percent
chance). Regardless of exact timing of precipitation and
associated cloud cover, less impressive ridging going into early
next week should allow temperatures to fall back to near
average in the mid to upper 70s.

MH

&&

.AVIATION...
Issued 238 PM CDT Tue Sep 17 2024

VFR conditions continue through the TAF period, aside from a few
pockets of ground fog along the Kettle Moraine and within river
valleys overnight into early Wednesday morning.

Light southeasterly winds throughout the day, with a more easterly
component along the lakeshore with a lake breeze. Winds will
become nearly calm overnight. Winds pick back up Wednesday
morning, again southeasterly. A lake breeze is expected again
Wednesday afternoon.

MH

&&

.MARINE...
Issued 238 PM CDT Tue Sep 17 2024

High pressure around 30.2 inches over the Northeast and low
pressure around 29.3 inches the northern High Plains will keep
winds light through Wednesday. High pressure will gradually
weaken and drift eastward on Thursday, with the low
strengthening to 29.2 inches. This will produce south-southeast
winds Thursday into Friday. In addition, a weak front will push
southeastward across the open waters Thursday night into Friday,
bringing showers and isolated thunderstorms. Low pressure will
slowly shift eastward toward the Great Lakes region this
weekend, with winds remaining generally southeasterly. As low
pressure approaches, additional showers and thunderstorm chances
develop, especially across the southern half of the Lake.

MH

&&

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

$$

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