000
FXUS63 KMKX 222044
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
344 PM CDT Mon Apr 22 2024

.KEY MESSAGES...

- Scattered thunderstorms possible Tuesday afternoon. Cannot
  rule out seeing a stronger storm or two capable of producing
  small hail and localized gusty winds ahead of the cold front.

- Potential for frost/freeze concerns return Tuesday night and
  Wednesday night.

- More active pattern with thunderstorm potential Friday into
  the weekend.

&&

.SHORT TERM...
Issued 341 PM CDT Mon Apr 22 2024

Tonight through Tuesday night:

Upper-level ridging today will slide east as mid-level trough digs
into the Upper-Midwest. Ahead of the main trough will be a broad
shortwave with a vort max ripple working across WI later this
afternoon and evening and be the main focus for scattered shower
activity. Trends continue to favor shower development along the mid-
level feature aligning with a a developing LLJ around 40-55 kt this
evening. All the 12z CAMs pick up on trend along with the global
models, with the greatest chances across the northern half of the
CWA. However, rainfall totals remain light with HREF and NBM have
medium to high probabilities (50-70%) of seeing measurable rain
north of I-94, but seeing 24hr QPF exceeding 0.1" remains low
(<40%). Main window for this activity will be between 23z-05z.

Otherwise, with the strong LLJ and tighter pressure gradient as the
associated low tracks across southeastern Manitoba/western Ontario,
southwesterly winds will remain elevated. Also will bring much
warmer overnight temps with lows in the mid 40s to low 50s.

Tuesday will be another warm day with breezy southerly winds as the
main upper-level trough swings and drags a cold front across the
region. While there will upper-level dynamics aligning with deep
layer shear exceeding 50 kt, min SBCAPE around a few hundreds of
J/kg along with some CAMs hinting at a few showers/storms
developing, any chances remain more scattered in nature. Dewpoints
will be tough to crack the lower 40F and PWATs will remain less the
0.7", thus moisture will be limited. However if we are able to get a
thunderstorm to develop and grow upscale, they could potential
produced localized gusty winds given the steep low-level lapse rates
indicated in the model soundings along with some small hail. Will
need to monitor trends over the coming hours, but the latest 18z
HRRR is favoring the drier solution.

Nevertheless, a cold front will slide through Tuesday
afternoon/evening with a secondary backdoor cold front sliding
southward overnight Tuesday. The secondary front will bring the
colder airmass into southern WI Tuesday night dropping lows into
30s. Given the CAA, the is a higher potential (60-80% chance)
to see frost/freeze conditions Tuesday night/early Wednesday
morning.

Wagner

&&

.LONG TERM...
Issued 341 PM CDT Mon Apr 22 2024

Wednesday through Monday:

As we enter the middle of the week, dry weather returns to southern
Wisconsin. Behind the exiting cold front Tuesday night, high
pressure will build into the Great Lakes Region from the Northern
Plains. This upper level ridge will mosey through the state
Wednesday into Thursday. Eventually exiting Thursday evening/night.
Wednesday will likely (70-80%) be the coldest day of the week with
cold air advection kicking in behind the cold front. High
temperatures Wednesday are expected to be in the 40s along Lake
Michigan to mid 50s further inland. With gusty east to northeast
winds coming off Lake Michigan, the cool air will have an easier
time traveling inland which will keep more than just the immediate
lakeshore cool. These cool conditions will be short lived as the
upper level ridge moves east of the state bringing a return of warm
air advection and clear skies to allow for more diurnal heating.
Thursday through Sunday will remain warm with temperatures expected
to be in the 60s to 70s.

For the end of the week and through the weekend, there will be
multiple chances for rain. Two separate troughs will advect out of
the Southwest CONUS toward the Great Lakes Region in the extended.
The first of which is expected to advance toward Wisconsin Friday
into Saturday. There are still some discrepancies between timing and
location on this low pressure system. The GFS has been a bit faster
and further north than the EURO and Canadian. Regardless of track
there is higher confidence (50% or greater) that southern Wisconsin
will get rain regardless of the track issues. The shifts that are
occuring are relatively small with the upper level trough and mid
level low pressure systems traversing the state, however the track
will play a roll in the duration, amount of rainfall expected, and
potential for any strong/severe thunderstorms.

As this system pulls out of the Great Lakes Region, right on its
heels will be that second trough advecting out of the southwestern
CONUS. This will bring the state another round of rainfall Sunday
into Monday. There is quiet a bit of uncertainty with this system
especially in regards to timing and location. This has created an
extended forecast dominated by POPs of roughly 40-90%. As the
weekend gets closer expect the timing for rain/storms to firm up a
bit with the added detail. Definitely a rainy weekend, but not
necessarily a washout at this point.

Patterson

&&

.AVIATION...
Issued 341 PM CDT Mon Apr 22 2024

VFR conditions prevail this evening with gusty southwesterly winds
persisting. Gust around 25-30 knots continue this evening and look
to remain elevated overnight. Winds will be accompanied by some LLWS
as a 45-55kt LLJ moves across the the area. Upstream radar shows a
broken line of showers working their way across the region and
should follow the trend of moving through central and southern WI
this evening mainly between 23z-05z. May see lower visibilities
accompany any shower activity, but ceiling height look to remain
above VFR levels. While cannot rule out a stray rumble of thunder,
chances remain very low. Cold front then expected to swing through
during the day Tuesday bringing a northerly wind shift. The cold
front will also bring another round of showers and potential for a
few thunderstorms Tuesday afternoon/evening, which may even be
capable of producing small hail and localized gustier winds.

Wagner

&&

.MARINE...
Issued 341 PM CDT Mon Apr 22 2024

Southwesterly winds have picked up over Lake Michigan as low
pressure tracks across southeastern Manitoba/western Ontario
overnight. Gusty winds will persist overnight into Tuesday as the
surface low and cold front slide into the Upper Great Lakes through
Tuesday afternoon. Small craft conditions expected during this time
and cannot rule out a brief gale force gust at times. Also could see
a few thunderstorms with the frontal passage as well. Expect gusty
winds to turn more northerly through the afternoon from north to
south. While cannot rule out a few gusts to gale force at times,
especially Tuesday evening, potential and coverage remains low
enough to hold back on any headlines at this time. Winds will begin
to lighten up Wednesday through the second half of the week as high
pressure builds down across the upper Great Lakes. Then southerly
winds increase heading into the weekend as another storm system
approaches.

Wagner

&&


.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM
     Wednesday.

&&

$$

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