Menomonee Falls, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

057
FXUS63 KMKX 180332
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1032 PM CDT Thu Apr 17 2025

.KEY MESSAGES...

- There are chances for thunderstorms late overnight. Hail and
  gusty winds may occur with the stronger storms.

- There are chances for thunderstorms mainly Friday afternoon
  and early evening, as a cold front moves through. If storms
  can develop, large hail and strong winds are possible,
  especially in southeast Wisconsin.

- High temperatures well into the 60s and 70s are forecast
  Friday, highest in southeast Wisconsin.

- Another system will come through Sunday and Monday, bringing
  widespread rain to southern Wisconsin.

&&

.UPDATE...
Issued 1030 PM CDT Thu Apr 17 2025

Currently observing a lull in activity as showers / weak
thunderstorms push northeast of Sheboygan. Things are looking
relatively quiet for the next 2 hours or so as the low-level
jet continues to intensify.

Referring to 925-850mb mesoanalysis charts, the LLJ will advect
a plume of higher temps / dewpoints into the region later
tonight, increasing the HREF mean MUCAPE to over 1000 joules
(with the HRRR producing 1200-1500 joules). After midnight we
expect thunderstorms to approach from the west, and between then
and the Friday AM commute, the threat for strong thunderstorms
with hail as the primary threat (possibly gusty winds) will be
present. As is often the case with elevated convection, CAMs
are unlikely to help us narrow down this wide time window, until
patterns on radar become evident.

Surface WAA ahead of Friday afternoon`s cold front then creates
a surface-based unstable environment over southeastern WI,
creating the Friday afternoon/evening strong storm threat, with
wind gusts and hail as equal threats. Front-parallel shear would
suggest the environment favors rapid upscale growth of any
convection into a line Friday afternoon along the front, yet
weak synoptic forcing for ascent (besides the cold front itself)
yields plenty of uncertainty on the exact timing and placement
of Convective Initiation (CI), though there is consensus that
any storms in southeastern WI would likely grow stronger than
elsewhere.

Most models favor late Friday afternoon / early evening CI
along the cold front (which could be along a Janesville to Port
Washington line, or one county east/west of there depending on
which model you choose), with the convection sweeping east with
the front thereafter. Models largely depict a cellular
convective mode, but as discussed above, the environment,
rather, would suggest rapid conglomeration into a line
(bolstering the wind threat). Either way, hail and damaging
wind gusts would be the main concern, and southeastern WI would
be the hazard area. Generally a level 2 out of 5 severe risk.
Scattered showers and weaker storms could also be present west
of the boundary throughout the day, but ultimately less
impactful.

A less likely scenario (generally not depicted in 00z models),
but one we must discuss, would involve a discrete cell or two
firing off in the warm sector (east of the cold front, in
southeastern WI) a bit earlier, perhaps mid Friday afternoon. In
the unlikely event this were to occur, said storm (or two)
would be capable of hail, wind gusts, or a brief tornado. This
scenario is less favored in guidance, due to the lack of forcing
for ascent.

Sheppard

&&

.SHORT TERM...
Issued 323 PM CDT Thu Apr 17 2025

Tonight and Friday:

Warm air advection may continue to bring scattered showers and
a few storms northeastward through parts of the area into this
evening. Mostly cloudy skies are expected to continue, with
gusty south to south southeast winds.

Still expecting scattered showers and thunderstorms to move
through the area later this evening and overnight, generally
entering between 10 PM and 12 AM CDT in the far west and exiting
between 3 AM and 5 AM CDT in the far east. The low level jet
increases and taps into increasing elevated CAPE and deep layer
bulk shear during this period across the area. Mostly sub-
severe hail is possible with the storms during this period, with
perhaps some gusty winds.

Thunderstorm potential on Friday afternoon and early evening
still is very conditional, as the cold front moves east through
the area. Mean layer CAPE and deep layer shear increases enough
for a risk for large hail and strong winds, if any storms can
develop. Despite clouds possibly lingering most of the day, warm
air and moisture advection will bring in highs into the 60s and
70s, warmest southeast, with dew points to around 60 degrees F.

The question will be if and where the storms form, as there is
little upper level support. CAMs seem to be trending more
towards developing convection along the front in northern
Illinois by middle to late afternoon, as the cap weakens. Some
develop more storms into southeast Wisconsin or initiate storms
in southeast Wisconsin, while others keep it south or southeast
of the area. Will continue to monitor this potential into early
Friday evening.

Wood

&&

.LONG TERM...
Issued 323 PM CDT Thu Apr 17 2025

Friday night through Thursday:

There may be some post-frontal showers and a few storms that
linger Friday evening, before drier air with cold air advection
arrives by later Friday night. High pressure should bring a dry
period to the area on Saturday and Saturday night, with cooler
but more seasonable temperatures.

Deterministic models and ensembles continue to bring a fairly
strong low pressure system and negatively tilted 500 mb
shortwave trough through the region mainly Sunday night into
Monday. Probabilities for 0.50 inches or more of precipitation
are over 50 percent for most of the area, with almost all
ensemble members showing a good wetting rainfall. Kept higher
end PoPs (around 80 percent) for Sunday night, with a ramp up of
PoPs Sunday afternoon and ramp down Monday afternoon.

Ensembles suggest mild temperatures gradually moving into the
region for the rest of next week, with periodic chances for
showers, as the 500 mb flow remains relatively zonal.

Wood

&&

.AVIATION...
Issued 1030 PM CDT Thu Apr 17 2025

A lull in shower / storm activity over the next two hours or so,
followed by gradual approach of stronger showers and
thunderstorms from the west overnight through the Friday AM
commute. Breezy south winds overnight. A low level wind shear
threat is already present, with a low level jet producing south
to southwest winds at 2,000 ft of 50 kts or more. This will
persist through the night into early Friday morning before
dissipating. Main concern with the overnight / Friday AM commute
storms will be small hail, a few storms may become strong to
severe with hail and gusty winds. Mostly VFR cloud ceilings
until storms arrive, then a gradual drop. MVFR and brief windows
of IFR looking likely at some point Friday AM.

From late Friday morning through early Friday afternoon,
expecting a general lull in shower / storm activity, followed by
additional showers / storms later Friday afternoon into the
evening along a cold front, with the strongest storms in
southeastern WI capable of wind gusts and hail. Winds veer
northwest behind the front.

Sheppard

&&

.MARINE...
Issued 323 PM CDT Thu Apr 17 2025

Breezy south to southeast winds will continue into tonight, as
high pressure slides east of the lake, and low pressure around
29.4 inches moves across the central Great Plains into Iowa. A
few gale force gusts are possible during this period over the
open waters of Lake Michigan.

A Small Craft Advisory continues tonight for the nearshore
waters for gusty winds and high waves, and continues into Friday
north of Port Washington. It may need to be extended south of
there into Friday, if gusty winds remain. There are chances for
thunderstorms mainly later tonight across the nearshore and open
waters of the lake.

Modest southerly winds on Friday will then shift northwesterly
late Friday afternoon or evening, with the passage of a cold
front. There are chances for thunderstorms later Friday into
Friday night with the cold front, with large hail and strong
winds possible over southern portions of the lake.

Modest northwest winds continue behind the cold front Friday
night, followed by lighter north winds Saturday, as high pressure
around 30.4 inches builds into the Great lakes region.

Wood

&&

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

     Small Craft Advisory...LMZ643 until 4 PM Friday.

&&

$$

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