477
FXUS63 KMKX 200836
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
336 AM CDT Sun Apr 20 2025

.KEY MESSAGES...

- Increased rain chances (+90%) for this afternoon into Monday
  morning with multiple waves of showers and few thunderstorms,
  especially this evening.

- The heaviest rainfall (>60% chance of exceeding 0.5 inch)
  will be west of I-39 corridor.

- Warm up Tuesday through the end of the week with well above
  normal highs and additional rain chances for the second half
  of the week.

&&

.SHORT TERM...
Issued 333 AM CDT Sun Apr 20 2025

Today through Monday:

A few low clouds are sneaking in from Lake Michigan into east-
central WI while high clouds try to working their way in from
the southwest. Expecting cloud cover to increase through the
morning as the high pressure pushes eastward while an upper-
level shortwave trough lifts across the Plains and becomes
inverted as it lifts into the Midwest this evening/tonight.
Ahead of the trough looking at 850mb WAA to lift across southern
WI this afternoon bringing the first wave of showers to the
area. Then expecting to see periods of showers through the
evening with more of a lull in southeastern WI as the associated
surface low lifts across eastern IA into south WI. Additional
wave of showers progged around the low as well ahead of it and
its cold front late this evening and overnight. The surface low
then is progged to lift across central WI into the northern half
of Lake Michigan Monday morning bringing additional wave of
showers on the backside. Mainly looking at this scattered shower
activity across the northern half of the CWA for Monday morning
before drier air pushes into the region for Monday afternoon.
Will see gusty winds with gusts up to around 30-35 mph accompany
the low pressure system as it works its way across the area as
well.

Overall most of southern WI will see rainfall from this event,
but areas along and west of I-39 corridor have the higher
potential to see higher rainfall totals. 00z HREF LPMM shows
24hr QPF ending Monday greater than half an inch for areas west
of line from Ripon to Janesville with areas around the lower
Wisconsin River Valley approaching and even exceeding an inch.
NBM along with the EPS, GEPS, and GEFS members show similar
trend in QPF amounts. Meanwhile areas further east of I-39 look
to see lesser amount as there continue to remain lower
confidence in 24hr QPF exceeding half an inch. Based on the 00z
HREF LPMM, generally looking at rainfall totals between 0.25-0.5
inch. However given some MUCAPE (200-400 J/kg) sneaking
northward into southern WI with the evening round of showers,
could see localized pockets of higher rainfall (>0.5 inch) with
any taller/persisting thunderstorms ahead/along the cold front.

As for temps, today looks to start mild, but increasing cloud
cover and easterly flow off of Lake Michigan will limit things.
Inland area look to top off in the mid 50s, while areas will be
cooler by the lake and may not even get out of the 40s. Monday
looks to see similar temps if not a few degrees cooler in the
50s as cloud cover lingers and CAA on the backside of the low.

Wagner

&&

.LONG TERM...
Issued 333 AM CDT Sun Apr 20 2025

Monday night through Saturday:

The surface and upper low will continue to linger over the
Great Lakes region Monday night with a period of surface high
pressure and upper level ridging. This period will be brief
however as a shortwave slides through Tuesday associated with a
weak low pressure system. The current track of this system takes
it through northern Minnesota with chances remaining fairly low
(30-40%) through the day Tuesday. However, into Tuesday
evening/night chances will increase (50-65%) as the region gets
an additional influx of moisture in the mid -levels with some
WAA/LLJ influence, particularly at 850mb. Some thunderstorms
could be expected, particularly into the evening hours.

Into Wednesday expect largely zonal flow aloft at least
initially with weak high pressure over the region. Expect dry
conditions through the day Wednesday but into Wednesday
evening/overnight through Friday become a lot more uncertain
though likely featuring at least some precipitation. Models are
all over the place with this next system but the general pattern
aloft shows a few shortwaves pushing through the region; one
coming from the southern plains with the other originating from
the Rockies. These will converge in someway or another later in
the week making for an active period of weather though likely
featuring some drier intermittent periods from Wednesday night
through Friday. Storms seem likely given the setup but some
models fail to bring instability up to the region but it depends
on the development of the system(s).

Into and through the weekend models seem to be more sold on
large scale ridging and high pressure overhead with a return to
quiet conditions across the region. This is not expected to be a
prolonged period of ridging, however.

Kuroski

&&

.AVIATION...
Issued 333 AM CDT Sun Apr 20 2025

A patch of lower clouds are sneaking southwestward off of Lake
Michigan bringing IFR/LIFR ceilings to SBM. Other areas along
the Kettle Moraine (UES, ETB, and at times SBM) are seeing
pockets of fog with lower visibility. These conditions look to
be limited and progged to improve through daybreak. Otherwise,
looking at high clouds to spread in through the morning into the
afternoon. Will then see multiple waves of rain spread into
southern WI this afternoon through early Monday morning. Areas
west of I-39 (MSN and JVL) will see more persisting rainfall and
lower flight conditions while areas further east are likely to
see more off and on type of showers this afternoon and tonight.
Also cannot rule out a few thunderstorms this evening/overnight
with any shower activity. As for the winds light winds will
gradually become easterly through the morning before increasing
and turning more southerly overnight as low pressure works its
way across southern WI.

Wagner

&&

.MARINE...
Issued 333 AM CDT Sun Apr 20 2025

The high pressure will shift eastward today as low pressure
lifts into the area from the southern Plains. Expect increasing
east to northeasterly winds to develop through the day as Lake
Michigan sits in between the departing high and an approaching
low. The low pressure will lift across the northern half of the
lake on Monday with gusty southerly winds then turning westerly
across the lake as it departs. Gusts to around 30 knots and
building waves are expected across the nearshore as well as the
open waters. Thus small craft advisory has been issued for this
evening through Monday. Also cannot rule out a few brief gale
force gusts, especially over the western and central portions of
Lake Michigan through Monday. Lighter winds are expected
Tuesday into the middle of the week as high pressure builds in
behind the early week system.

Wagner

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...7 PM
     Sunday to 7 PM Monday.

&&

$$

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