387
FXUS63 KMKX 032037
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
337 PM CDT Mon Jun 3 2024

.KEY MESSAGES...

- There is a Slight Risk (level 2 out of 5) for severe
  thunderstorms this afternoon and evening, with damaging wind
  and small hail as the primary threats. An isolated tornado
  cannot be ruled out. Heavy rain becomes the main threat
  tonight.

- Warm/muggy conditions continue through Tuesday.

- Thunderstorms are expected to develop Tuesday afternoon. An
  isolated severe storm with wind and hail possible during the
  afternoon to evening hours. Additional thunderstorms develop
  Tuesday night into Wednesday along a cold front.

- Northwest winds bring cooler and drier air to southern
  Wisconsin for the second half of this week.

&&

.SHORT TERM...
Issued 337 PM CDT Mon Jun 3 2024

Tonight through Tuesday night:

Showers and storms have developed along the MCV boundary along the
Mississippi River. These storms are expected to progress east
northeastward tonight and combine with a lingering boundary
draped from Port Washington to Madison, leading to severe
weather potential across southern and southwestern Wisconsin.
The primary threat with these storms looks to be wind, with
surface based CAPE values near 2000 J/kg in southwestern
Wisconsin and close to 1000 J/kg in southeastern Wisconsin
combining with PWATs near 1.5 inches and equilibrium levels near
40 kft to produce favorable conditions for wet microbursts.
Threat for large hail (greater than one inch in diameter) still
exists within stronger cells, especially going into this
evening. However, mid-level lapse rates only near 6.5 degrees
C/km is expected to inhibit explosive growth and mitigate hail
sizes.

Mesoscale modeling is indicating SRH in the lowest km will
increase to near 100 m2/s2 into this evening as storms develop
cold pools, leading to a chance for an isolated tornado along
line segments.

As storms become cold pool dominant late tonight, heavy rain
becomes the primary threat. PWAT values are forecast to be near
1.5 inches, with warm, moist southeasterly to southerly flow
throughout the overnight hours. Storms that manage to develop
parallel to shear may produce training thunderstorms that
produce heavy rain. MUCAPE remains around 700 J/kg throughout
the overnight hours, so generally not expecting all PWATs to be
realized as rainfall. However, the environment is primed for
heavy rainfall and flooding potential will be monitored tonight.

Rain diminishes and moves out into Tuesday morning, with
clearing skies and continued southerly flow bringing in
additional instability and assisting with atmospheric recovery.
Surface based CAPE values near 2500 J/kg are possible, with a
few CAMS indicating solutions up to 3000 J/kg. A shortwave
moving northeastward through southern Wisconsin will then have
the potential to kick off additional thunderstorms in this
primed airmass. Bulk shear values remain near 25 kt, which may
provide a mitigating factor in severe weather. However, damaging
wind gusts and hail are possible within stronger thunderstorms.

MH

&&

.LONG TERM...
Issued 337 AM CDT Mon Jun 3 2024

Wednesday through Monday:

The main cold front that is associated with an extension of vorticity
that stems from a closed upper low stationed over central Alberta
Canada will push through WI early Wednesday. The showers and
thunderstorms along that front are expected to clear southeast WI
by mid morning, but likely by 7 AM. Another shortwave trough that
is rounding the base of the closed upper low will slide into
southern WI during the late afternoon or evening. This will help
to steepen the low and mid level lapse rates over southern WI and
allow for scattered showers. Models are not showing super steep
rates right now because the wave might come through past the peak
daytime heating, so thunder seems less likely, but kept the
mention in the forecast for now.

We will remain under that cyclonic flow until Friday night when
the upper low finally shifts into the eastern Great Lakes region.
Highs will be in the lower 70s Thu-Fri, with lows in the lower
50s. There may be scattered afternoon showers each day, but
moisture might be too sparse. There will at least be widespread
diurnal cumulus clouds each day.

Yet another weak shortwave should move through Saturday afternoon
and night, thus another chance for showers and storms. More
sunshine, slight ridging, and a little return moisture will allow
for temps to get back into the mid-upper 70s for the weekend.

Cronce

&&

.AVIATION...
Issued 337 PM CDT Mon Jun 3 2024

Scattered thunderstorms are expected across southern Wisconsin
through tonight. Ceilings have generally remained VFR, but a few
pockets of 15 to 25 kft cloud decks have developed within
heavier activity. Storms slowly pushing eastward in far southern
Wisconsin remain capable of producing damaging wind gusts up to
50 kt and small hail. An isolated tornado is unlikely, but
cannot be ruled out into the evening hours. Heavy rain is
possible along Lake Michigan and in far southern Wisconsin
tonight as storms redevelop over the same areas. Storms diminish
late tonight, with patchy fog expected in valley areas.
Southerly breezes will largely diminish tonight after storms
move through, increasing again into Tuesday morning.

MH

&&

.MARINE...
Issued 337 PM CDT Mon Jun 3 2024

Low pressure centered over northern Minnesota will continue to
weaken and light southerly winds will persist. Dense fog is
possible over the north half tonight, but there is not enough
confidence to issue a headline at this time. Patchy dense fog is
possible in nearshore regions as well after rain and storms
exit.

A low pressure trough will cross the Northern Plains tonight
through Tuesday. Southerly winds are expected ahead of the
associated cold front. Showers and thunderstorms are expected
through late tonight and again Tuesday afternoon and evening.
The cold front will cross Lake Michigan early Wednesday morning
and the widespread showers and storms will end. Winds will veer
westerly and scattered showers are possible each afternoon
through the weekend. Winds may approach Small Craft Advisory
criteria at times during this period. Westerly winds continue
through the end of the week as low pressure over south central
Canada weakens.

Cronce/MH

&&

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

$$

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