NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 301958
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
258 PM CDT Mon Mar 30 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected this evening
  into tonight, mainly from 8 PM CDT onwards. A few storms could
  be severe, with large hail up to 1.5 inch diameter being the
  primary threat.

- Additional showers and storms are forecast Tuesday morning and
  afternoon, with exact areas of development depending on early
  day clouds/rain and front timing. A few storms could be
  severe, with large hail and gusty winds being the primary
  threats.

- Increasing potential for snow, sleet and freezing rain along
  and north of Interstate 94 Wednesday evening into Thursday
  morning. Impacts to the Wednesday evening and Thursday morning
  commutes possible.

- Additional chances for rain and a few thunderstorms Friday
  afternoon into Saturday.

&&

.SHORT TERM...
Issued 230 PM CDT Mon Mar 30 2026

Rest of Today through Tuesday night:

Two frontal zones are beginning to take shape across southern
WI at the moment, and are slowly morphing into one. The first
is a stalled warm front spanning from roughly Montello to West
Bend, and the second is a lake-breeze front from West Bend to
Milwaukee to the shoreline of Kenosha county. South and west of
these boundaries, we have southwesterly surface flow advecting
warmer air and dewpoints in the 50s into the area. North and
east of the boundaries, lake-refrigerated air is holding it's
ground. Meanwhile (as of 230 pm CDT), in eastern Nebraska we
can see a shortwave trough lifting northeastward towards our
region, with ACCAS clouds visible on GOES satellite imagery.
This perturbation will serve as the focal point for thunderstorm
activity when it reaches our region this evening (mainly after
8pm CDT). CAMs are all over the place when it comes to the
location of convective initiation, with models like the NAM 3k
preferring a surface frontal-based initiation towards central WI
later in the evening, and the HRRR firing precipitation from
the ACCAS in northeastern IA earlier in the evening which would
allow storm-scale dynamics to take over and track storms
towards far southern WI. With the wide range of CAM solutions,
it's too early to advertise a 'threat area' for this evening's
convection, but in any case, a fraction of the CWA is likely to
see scattered thunderstorms this evening.

Ingredients are present this evening through tonight for a few
strong to severe storms with hail up to 1.5 inches in diameter
(level 2 out of 5 severe threat). Roughly 1,000 to 1,500 joules
MUCAPE and 850-500 mb Lapse Rates in excess of 8 C/km are
expected with this evening's convection, with the LLJ likely to
rapidly replenish these values after the initial wave of
convection. Hence, though many CAMs resolve a several hour long
lull in convection late tonight into early Tuesday morning, we
certainly can't pin down when (or if) this lull would occur, and
an additional severe storm later tonight into Tuesday cannot be
ruled out.

Additional showers and thunderstorm chances continue into
Tuesday morning with this same activity, with the MUCAPE values
gradually diminishing later in the morning (severe threat
decreases to level 1 out of 5 post-dawn Tuesday). The
aforementioned frontal boundary will sag southward across the
region at some point later Tuesday morning through early Tuesday
afternoon, with areas along and just behind this front becoming
a focal point for additional organized storms, with hail as the
primary threat, and some gusty winds as a far secondary concern.
Timing of any morning convection will determine the potential
for airmass recovery in advance of the front, thus determining
the exact risk level & timing. Any lingering showers / weak
storms should be confined south of or near to the WI/IL border
by Tuesday evening, leaving predominantly dry weather for our
region Tuesday night.

Sheppard

&&

.LONG TERM...
Issued 230 PM CDT Mon Mar 30 2026

Wednesday through Monday:

An active mid week and weekend ahead for Southern Wisconsin. The
first "round" of precipitation comes late Wednesday through
Thursday. Then a second "round" will follow quickly behind for
late Friday through Saturday. Then some quieter conditions look to
move in for Sunday and Monday.

Kicking things off with the first round, there will be a low
pressure system that develops in the central and southern Plains
Tuesday and then advects toward the Great Lakes Region for
Wednesday evening into Thursday Evening. There is fairly good
consensus on from 500 mb to the surface that this shortwave will
move northeast into the region. The one question on track that
remains is will this pass just to the south of the state, through
northern Wisconsin or somewhere in between. There is a lot of
variability between the deterministic and ensemble members. The
track will be very important in regards to the potential for mixed
precipitation.

A track through southern Wisconsin (which looks the most likely
with this model run), would start out with southwest winds WAA and
the LLJ moving into the area. This would result in a large
area/deep area of above freezing temperatures and dewpoints in
forecast soundings. This will kick precip type off with mostly
rain. As temperatures cool overnight, both at the surface and
aloft, the concern for mixed precipitation grows. The best chances
for freezing rain, sleet and snow will be for areas north of
Interstate 94 with this track. Since there is a lot of
variability, CAN deterministic is much further north which favors
more rain should the sfc low fallow a similar path. This would
shorten the window of cooler temps overnight and limit how cold it
gets which will leave precip types in the rain and freezing rain
department (mostly rain). A more southward track, deterministic
GFS and few ensemble runs from the same model set favor more snow
and sleet. Snow chance would extend further south toward the WI/IL
border in this scenario as well. Make sure to keep up to date
with the forecast for this mid week system as confidence is high
on the chances for precipitation (70-95% chance), but the
fluctuation in precipitation type be a big determining factor on
the expected impacts. Wednesday evening and Thursday morning
commutes are the most likely to see impacts.

The next "round" of precipitation will come Friday evening through
Saturday as another upper level trough and sfc low move toward
Wisconsin from the Rockies. Temperatures overall are trending
warmer than the midweek system (based on the low track), which
will bring chances for rain and thunderstorms (60 to 80% chance).
If the low tracks further south there could be some changes to the
precipitation type, but overall guidance is trending warmer. This
is further supported by the dipole pattern for 500 mb Cluster
Analysis. The dipole distribution supports uncertainty in the
timing and location of the trough.

Beyond this system high pressure looks to build into the Great
Lakes Region for Sunday and Monday which will bring much quieter
and near normal temperatures for the start of the week.

Patterson

&&

.AVIATION...
Issued 230 PM CDT Mon Mar 30 2026

Dry weather and VFR through the rest of this afternoon, with a
south to southwest breeze for most inland and southern WI
terminals, and a developing southeast to easterly lake breeze
along the Lake MI shoreline. East to northeasterly flow is
ongoing for portions of east-central WI (KFLD and KSBM) and is
likely to fill in ~1 county further south over the next few
hours.

Scattered showers and thunderstorms expected to build into our
region from the southwest this evening into Tonight (mainly 8 PM
CDT and onwards). Exactly where these storms setup (in the
southern WI region) is not yet certain, but a level 2 out of 5
threat for strong to severe storms is present across our entire
area, with large hail (up to 1.5 inch diameter) as the primary
concern. A southwesterly LLJ nosing into southern WI this
evening through tonight will lead to LLWS as reflected in the
TAFs (azimuth-230 at 45 to 50 kt). LLWS was left out of the
KSBM TAF, but the latest model trends suggest the LLJ may cross
east-central WI too (might be added in a future TAF Amendment).
Cloud ceilings with the TS activity this evening into tonight
should initially arrive at VFR altitudes (likely well over 5,000
ft), and may stay that way through much of the night. A lull in
the shower / thunderstorm activity is likely after the first
round of storms rolls through, though the LLJ will likely
attempt to fire additional showers / storms later in the night
through Tuesday morning. Any repetitive hits from showers /
storms could result in reduced ceilings.

The colliding airmasses / wind patterns discussed in the first
paragraph forms a sharper frontal boundary later today into
tonight, which will sag southward as a cold front on Tuesday.
The exact timing of the frontal passage is uncertain (perhaps
late morning to mid afternoon), but with it we expect a briefly
higher concentration of showers / thunderstorms and north winds
arriving behind it. Mixing airmasses along the leading edge of
the front coupled with rain-humidified air are likely to cause
ceilings to fall to Fuel Alt MVFR or IFR levels in a north to
south manner Tuesday morning, followed by a gradual improvement
behind the front Tuesday afternoon.

Predominantly dry weather expected for Tuesday evening, with
any lingering showers / storms mostly confined along and south
of the WI/IL borderline.

Sheppard

&&

.MARINE...
Issued 230 PM CDT Mon Mar 30 2026

A frontal zone will sharpen over Lake Michigan today, with north
to northeasterly flow over northern portions of the lake and
southerly flow further south. The boundary between these two wind
patterns has setup along a Sheboygan WI to Manistee MI line
early this afternoon, but should sag south to a Milwaukee WI to
Whitehall MI line into this evening (approximately), with both
wind flows becoming stronger far north and far south of the
boundary. Some 20 to 30 kt gusts may occur over the northern and
southern thirds of the lake this evening into tonight as the
boundary sharpens. Rounds of showers and thunderstorms are
expected tonight into Tuesday across the lake, with a few
stronger storms possible at times (particularly near the
frontal boundary). Large hail would be the primary threat with
any stronger storms.

The boundary sags further south as a cold front Tuesday
afternoon, focusing lingering shower and thunderstorm activity
over southern Lake MI before washing it away later Tuesday.
Gusty north winds build in behind the front Tuesday evening into
Wednesday, with 20 to 30 kt gusts. Winds veer northeasterly
through Wednesday.

30.7 inch high pressure will shift from Ontario to Quebec through
the late week time period as 29.7 inch low pressure approaches
from the southwest, allowing winds to trend east-northeasterly.
Will need to watch for gale potential later this week
(particularly Thursday) as the low pressure system approaches
the lake.

Nearshore Zones:
The wind fields well north and well south of the aforementioned
frontal zones (tonight through Tuesday night) may occasionally
lead to Small Craft Advisory level winds and waves, as well as
sudden shifts in wind direction. Small Craft Advisories and
Marine Weather Statements may be needed. Strong to severe
thunderstorms are possible Tonight into Tuesday, with hail as
the primary threat. Stay tunded in case a Special Marine
Warnings become necessary.

Potential for Advisory-level wind gusts and waves lingers
through the rest of the forecast period as well.

Sheppard

&&

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

$$

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