West Allis, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

470
FXUS63 KMKX 112014
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
314 PM CDT Sat Apr 11 2026

.KEY MESSAGES...

- Highs in the 70s return Sunday through much of next week.

- An active weather pattern returns Sunday through next week.
  Warm and humid conditions and more showers and storms are
  expected. Severe storms will be possible.

&&

.SHORT TERM...
Issued 315 PM CDT Sat Apr 11 2026

Tonight through Sunday night:

Clouds have increased as WAA/moisture has increased in the
midlevels. We will continue to see a few splats of rain this
afternoon though given drier low levels this will likely
isolated to scattered activity. As we head later into the
afternoon, low levels should steadily moisten as the LLJ slides
east and rain will become more likely this evening. The warm
advection aloft will cause some weak MUCAPE to build to 500 J/kg
and some rumbles of thunder may occur early Sunday morning.
Overall the moisture will be more consistent throughout the
column with no significant dry air to work around but CAMs
generally show a scattered nature to activity with better
chances building to the northeastern CWA into the evening.
Evening chances will be best in the central/northeastern parts
of the CWA.

However, based on observations from last night WPC had pointed
toward a marginal risk for heavy rain as the outlier ARW model
performed best last night in the central US. This CAM (and to a
lesser degree the FV3) in particular shows a convective area of
storms developing to the west and southwest this afternoon and
pushing in during the evening. This shows an extended period of
rain showers tonight across southern WI and with PWATs in the
1.25-1.5 in range we could very easily yield some heavy rain
concerns overnight. But there remains uncertainty given the
differences in the CAMs. It is worth mentioning the 12z HRRR
shows an similar feature initially though it pushes through more
quickly and does not hold precip through the late night period.
Normally, we would rule out the outlier scenario for the most
part, but it cannot be ignored given that it best handled the
convection in the central US last night and that a few other
CAMs have hinted at this possibility, just perhaps not to the
same degree. Low lying areas may be susceptible to ponding and
minor flooding concerns. Flash flooding is not expected.

Rain may linger into the day Sunday but most CAMs having things
largely dry from mid morning through the mid to late afternoon.
Then later Sunday into Sunday night we will see a shortwave
track through with plenty of moisture and some additional WAA
from the LLJ over the area. At first look, this setup appears
harmless and looks fairly benign. However, digging deeper, the
environment out ahead of the precip associated with the
shortwave briefly becomes favorable for severe weather. The
global models generally show moist adiabatic soundings but the
HREF instability shows perhaps a bit more to tap into (~500J/kg)
and with fairly strong shear in the low levels of 30kts or so
and deep layer shear around 40kts. This potential is only for
the very forefront of precip pushing, which in several models
shows isolated to scattered convection pushing in. With non-
zero STP and modest supercell composite we cannot rule out any
hazard as brief as it may be (~2-4 hour period, 3-7pm). Further
into the evening precip will become more widespread with some
embedded storms. Periods of moderate rain with heavier rain in
storms should be expected and given PWATs across SE half or more
of the CWA of 1.25-1.5 in we could see another period of minor
flooding concerns, though no flash flooding is expected.

Kuroski

&&

.LONG TERM...
Issued 315 PM CDT Sat Apr 11 2026

Monday through Saturday:

Into Monday, models have trended largely dry during the day and
possibly even through Monday night. A strong inversion aloft
with limited forcing over southern WI may limit convective
potential at this time. Northern and possibly central parts of
WI will see better potential into the late afternoon/early
evening for storms given a much weaker inversion, closer to the
warm front that may yield better convective potential. Currently
southern WI is expected to be south of the warm front, perhaps
well south. Global model ensembles somewhat disagree with the
EC Ens having the warm front further south, toward central WI,
while the GEFS generally has the warm front much further north.
In addition, all of the CAMs we have that stretch into Monday
afternoon/evening suggest the further north setup with storms
largely remaining well to the north, with our CWA remaining dry.
Now we cannot rule out the EC setup but it has largely been the
outlier for this expected stretch of storm activity for this
upcoming week. The EC appears to just be on the slow side and in
this case it keeps the surface low much further south and west
which then keeps the warm front further south and within our
window of risk. Should the EC be correct this would put our CWA
in the primary risk area with all hazards possible given the cap
gets eroded. If the cap doesn`t get eroded, likely nothing
happens because there will be limited forcing aloft to get
elevated convection. However, assuming the cap erodes all hazard
would be possible given high instability environment with plenty
of low level and deep layer shear. The most likely timeframe for
the cap to erode, should it erode, would be Monday evening,
especially if the warm front is not present over the area.

Tuesday still generally appears to bring higher end severe
potential but the trend in the models has definitely shifted
toward a much more delayed progression of the upper level
trough, thus delaying the progression of the surface low.
However this has largely just shifted the how and why of the
system, only slightly lessening the higher end severe weather
concerns. Models do disagree on what is expected to occur across
southern WI but general models show a warm front now laying
across parts of southern WI with higher instability of 1500+J/kg
MLCAPE with decent deep layer shear around 40-50kts with fairly
large CWASP. The primary change is that the low level shear
appears to be weaker now or at least more uncertain than in
previous models. This will be something to monitor as Tuesday
approaches. In either case we will likely to be surface based
with capping initially but likely eroding by the late afternoon.
Plenty of uncertainty still to be worked out as models still not
in alignment in a lot of ways but the concern for severe storms
persists with all hazards possible.

Wednesday is the day that has changed most drastically, with
the delayed trough aloft. This delay in the arrival of the
trough actually brings the low through Wednesday
afternoon/evening with a highest end severe risk possibly
shifting to Wednesday. Still some uncertainty in regard to
timing and such but great instability and low to deep layer
shear with all hazards being possible. Model differences will
certainly still play a role but most of the models show a higher
end CWASP over the area indicative of the higher end
severe/tornado potential into Wednesday now.

It becomes a bit of a cluster beyond midweek as temperatures and
flow remain favorable for warm temperatures, instability and the
potential additional impactful systems. Specifically, next
Friday (possibly Saturday) may provide us with additional
storms and severe weather potential. Next week is shaping up to
be a very active week of weather for southern WI.

Kuroski

&&

.AVIATION...
Issued 315 PM CDT Sat Apr 11 2026

An area of rain showers may continue to push east northeast across
portions of the area this afternoon, though they may slowly weaken
as they encounter drier air. VFR clouds should continue to spread
across the area this afternoon and evening, with ceilings
gradually dropping to 3500 feet AGL this evening.

A period of low level wind shear conditions are expected from
mid- evening into early to mid-morning on Sunday across all
terminals.

An area of showers and a few storms should move east northeast
across the area from mid-evening into the overnight hours, ending
by early to mid-morning Sunday.

Ceilings should gradually drop into the 1000 to 2000 foot AGL
range for Madison and Sheboygan terminals, with higher values
toward the Milwaukee and Kenosha terminals. These ceilings should
rise above 3000 feet AGL for most of the area Sunday mid-morning
into the afternoon, perhaps staying around 2500 feet AGL toward
Madison. May see local visibility reductions to 3 to 5 miles
within any heavier rain shower areas.

Southeast winds this afternoon and evening should become south to
southwest later tonight into Sunday morning, becoming gusty by
late morning into the afternoon. These winds should prevent a lake
breeze from occurring for terminals near Lake Michigan.

Wood

&&

.MARINE...
Issued 315 PM CDT Sat Apr 11 2026

Southeast winds return this afternoon and become gusty tonight
as a sharper pressure gradient moves over Lake Michigan as low
pressure moves into the northern Great Plains.

Low pressure will shift into the northern Great Plains during the
day Sunday as it deepens to near 29.4 inches. The low will quickly
shift east toward Lake Superior Sunday night, reaching the
southern shores of the Hudson Bay by daybreak Monday morning.
Winds will thus increase further across the open waters Sunday
through Sunday night. Will be monitoring for gale potential
during this time frame, particularly over the northern half of
Lake Michigan. As of this forecast update, forecast models
continue to suggest possible gales and headlines may be needed in
the coming days.

Winds will weaken Monday morning as high pressure of 30.0 inches
moves across Ontario. Then, passing low pressure systems will lead
to persistently active conditions across Lake Michigan into next
week. Will need to monitor thunderstorm development during the
Monday- Wednesday time period, as some storms could become strong
to severe.

Kuroski

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...1 AM
     Sunday to 4 AM Monday.

&&

$$

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