National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KMKX 181540
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1040 AM CDT Thu Apr 18 2024

.KEY MESSAGES...

- Another round of light rain today into this evening.

- Cooler pattern through the weekend may result in frost
  concerns Saturday night, especially in the Wisconsin River
  Valley.

- Dry pattern through this weekend, but a chance for rain
  Monday evening through Tuesday morning.

&&

.UPDATE...
Issued 1022 AM CDT Thu Apr 18 2024

Off and on light showers will continue across southern WI today
as the surface lows lifts to northeast across IL this
afternoon/evening. May see rainfall rates pick up a bit more,
especially along the WI/IL border this afternoon as the low and
better upper-level dynamics move into the region. Otherwise,
expecting drier conditions on the backside of the departing low
this evening. While cannot rule out some light wrap around
showers across central WI counties on Friday from a low further
north meandering across central Ontario, mainly expecting mostly
dry conditions Friday into the weekend.

Wagner

&&

.SHORT TERM...
Issued 330 AM CDT Thu Apr 18 2024

Today through Friday:

Clearing skies will last for a few more hours with weak high
pressure prior to to a combination of 850-700mb frontogenesis
and some upper level shortwave activity push in bringing rain
chances (80+%) across the CWA. The other factor that adds
certainty to this is the moisture in the low to mid levels
especially but WAA and a being on the nose of the LLJ also helps
add forcing to this system. While these factors are not exactly
overlapping simultaneously but the various forcing mechanisms
will likely yield at least scattered showers. In the morning
models are suggestive of consistent showers across the
northwest/west part of the CWA with largely the frontogenesis
being responsible. A few CAMs are indicating some of the morning
showers that may (40%) leak further east would likely be
associated with the LLJ/WAA.

Showers will start to push further east into the afternoon as
the upper level shortwave activity slides east. The southeast
part of the area from Janesville to Milwaukee and south may
(40%) see a period of heavier rainfall in the late afternoon to
early evening as this system slides out. We could (10%) even see
a rumble of thunder as forcing mechanisms align a bit with
convective aspects (better lapse rates) and higher PWATs (1-1.25
in) allowing for some heavier and more efficient rainfall. Rain
will likely (90%) push out during the first few hours of the
evening. We will start to see clearing skies overnight as higher
pressure nudges in.

Friday looks largely to be quiet with higher pressure dominating
the region. Clear skies may (70%) largely remain despite the
upper low rotating and slowly pushing east due mostly to dry
upper level air. However by the late afternoon some clouds could
impinge on the CWA from the north and south though the sky would
at most be scattered higher clouds. Otherwise with cooler air
filling in, expect highs not get out of the upper 40s to low
50s. In addition the most impactful thing Friday will be the
west to northwest winds which will gust from 30-35 mph with a
gust or two to 40mph possible (30%). This will be due to decent
mixing in the afternoon of winds aloft and a strong pressure
gradient between low pressure to the north and higher pressure
strengthening and impinging from the west.

Kuroski

&&

.LONG TERM...
Issued 330 AM CDT Thu Apr 18 2024

Friday night through Wednesday:

Through the weekend the upper levels will remain very active
with the upper low gradually pushing out and various shortwaves
continuing through the region. However due to the lack of
moisture in addition to the modest high surface pressure
over the region, not only is precip not expected but skies
should remain mostly clear though Saturday could feature some
cloud cover.

Into early next week, Monday evening through Tuesday morning,
we should expect the next system to roll in. This will largely
be upper level shortwave activity in combination with some
LLJ/WAA influence that looks likely to bring at least some
showers across southern Wisconsin. The certainty with this
system has increased as the moisture and forcing mechanisms are
better defined in latest models.

By mid to late next week high pressure and an upper level ridge
should dominating the region with the next best chance for
precip being the following weekend with the high pressure
sliding out.

Kuroski

&&

.AVIATION...
Issued 1030 AM CDT Thu Apr 18 2024

Off and on showers with high ceilings persist through the
afternoon with mainly VFR conditions given recent trends.
However, may see rainfall rates pick up this afternoon as the
surface low lifts into IL, which would bring lower visibilities
and ceilings. The heavier rainfall along with lower flight
conditions look to favor areas along the WI/IL border through
the early evening. Then rain chances diminish between 01-04z as
drier air settles in behind the low, but lower ceilings around
MVFR levels may linger longer later this evening. Otherwise,
expect light variable winds to turn more northwesterly through
the night before increasing during the day Friday with gusts to
30kt.

Wagner

&&

.MARINE...
Issued 330 AM CDT Thu Apr 18 2024

Another low pressure area will deepen across Ontario today into
northwest Quebec for late tonight into Friday. With a
strengthening high pressure in western Canada impinging
southeastward the pressure gradient will sharply increase for
Friday across the region leading to breezy westerly winds across
the lake during this time. However, winds are not expected to
be as strong as over land due to the cooler waters of the lake.
However, we have issued a Small Craft Advisory from 15z Friday
to 0z Saturday for breezy west to northwest winds. Through the
weekend the high pressure will weaken as it slides southeast
meaning winds will trend lighter while remaining largely from
the west to northwest. May need a brief Small Craft Saturday but
it remains uncertain at this point.

Kuroski

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...10 AM
     Friday to 7 PM Friday.

&&

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSMilwaukee
www.twitter.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee