Big Bend, Wisconsin Weather Forecast Discussion

831
FXUS63 KMKX 210224 AAA
AFDMKX
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
924 PM CDT Sat Sep 20 2025
.KEY MESSAGES...
- A few thunderstorms may occur into the overnight hours, with
  patchy fog possible.
- Additional shower and thunderstorm chances (20 to 30 percent)
  are forecast Sunday into Monday.
- Mild temperatures are expected Sunday, with near normal
  temperatures into the start of the work week.
&&
.UPDATE...
Issued 924 PM CDT Sat Sep 20 2025
The main negatively tilted 500 mb shortwave trough continues to
slowly shift northeast through the area into the overnight
hours. Scattered showers and a few thunderstorms were continuing
in northern and western portions of the area, where some weak
differential CVA was working with weak instability and
moisture lingering in the low levels. There may be some very
weak warm air and moisture advection that would bring a brief
shower or storm overnight as well. Will adjust the forecast for
generally lower PoPs in the 20 to 30 percent range, and may need
to go even lower with the lack of a good upward vertical motion
mechanism.
There may be some patchy fog overnight into early Sunday
morning, with light winds and lingering low level moisture. The
very weak warm air/moisture advection and weak differential CVA
from passing vorticity maxima aloft should continue 20 to 30
percent chances for showers and a few storms into Sunday and
probably into Monday. Mild lows in the upper 50s to lower 60s
tonight are forecast, with highs in the middle 70s on Sunday.
Wood
&&
.SHORT TERM...
Issued 317 PM CDT Sat Sep 20 2025
Tonight through Sunday night:
Starting to see the scattered showers and thunderstorms
redevelop this afternoon along the axis of highest instability
(SBCAPE 1000- 2000J/kg) ahead of the upper-level low. This
activity will gradually work its way across the eastern half of
the CWA through the evening. Could see more widespread
development blossom as the frontal boundary lifting
northeastward interacts with a lake breeze.
Accompanying any showers and thunderstorm would be moderate to
heavy rainfall along with lightning. While effective shear
remains less than 25 knots, expect more pulse/multicell type
storms with this activity. Given PWATs above 1 inch and slow
movement of this convection, cannot rule out localized
ponding/minor flooding potential especially if storms move over
the same area for period of time. Also with low-level lapse
rates between 7-8C/km and pulse type nature, could see a few
weak downburst capable of producing +40 mph wind gusts at times.
Much of this activity is progged to linger into the start of
the evening, but gradually diminish as we loose daytime/peak
heating. But some showers may linger overnight similar to
previous night, but just further east. However, the upper-level
trough lifts north overnight and mostly dry conditions expected
into Sunday morning.
Then shower and storm chances return Sunday late morning into
the afternoon as another upper-level shortwave trough swings
down across WI. Given the additional rain chances and lingering
cloud cover expect temps to be on the cooler side with highs on
Sunday in the 70s.
Wagner
&&
.LONG TERM...
Issued 317 PM CDT Sat Sep 20 2025
Monday through Saturday:
The upper-level looks to slow down and potentially even cutoff
from the upper-level sitting over the Upper Great Lakes into the
start of the work week. Thus, will see rain chances through at
least Monday. May see enough drier air from a high pressure
working across Canada sneak down for Tuesday bring a brief
reprieve from rain chances. However, mid-range models generally
agree on another trough to dig across the Plains and lift into
the Midwest by midweek. This system looks to bring a surface
south of WI, placing our neck of the woods on the north/cool
side of this system. So may see additional shower chances return
to part of the area midweek onward. Otherwise, temps return to
near normal Monday through the end of the week with highs in the
lower 70s and lows in the 50s.
Wagner
&&
.AVIATION...
Issued 924 PM CDT Sat Sep 20 2025
Scattered showers and a few thunderstorms were continuing in
northern and western portions of the area. A brief shower or
storm may occur overnight as well. For now, may lean toward
PROB30 groups in the TAFs, with brief visibility restrictions
at times.
There may be some patchy fog overnight into early Sunday
morning, with light winds and lingering low level moisture. Not
sure how much fog may occur and how plentiful it may be, so will
keep visibility values above 3 to 4 miles at Madison and
Janesville for now.
Chances for showers and a few storms will linger into Sunday
and probably into Monday, so PROB30 groups may continue to be
utilized in TAFs. Light south to southeast winds should become
southwest Sunday for area terminals.
Wood
&&
.MARINE...
Issued 924 PM CDT Sat Sep 20 2025
Gusty east winds will linger across the northern third of the
lake into the overnight hours, before weakening by early Sunday
morning. The rest of the lake will continue to see lighter
southeast winds, as high pressure around 30.4 inches moves well
east of the region.
Light south winds are then expected to develop Sunday, with
light south to southwest winds Sunday night into Monday. High
pressure around 30.2 inches to the northeast of the region will
then bring north to northeast winds on Tuesday. Low pressure
around 29.8 inches should move from the Central Plains and skirt
south of Lake Michigan Wednesday, bringing increasing winds and
a more easterly wind shift by Thursday.
Wagner/Wood
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&
$$
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NWS MKX Office Area Forecast Discussion