378
FXUS63 KMKX 030314
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1014 PM CDT Sun Jun 2 2024

.KEY MESSAGES...

- Warm/muggy conditions prevail for the first half of this week.
  Multiple rounds of showers and thunderstorms Monday through
  Wednesday. There is a small, conditional potential for severe
  storms Monday afternoon.

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

&&

.UPDATE...
Issued 1005 PM CDT Sun Jun 2 2024

All eyes on the upstream convection making its way across
eastern NE tonight. Most of the 00z CAMs show this MCV weakening
as it tracks across IA and dissipating before it reaches the
western half of our CWA as outruns the instability. However, the
potential outflow may be enough to trigger a few scattered
showers across southwestern WI in the morning, thus cannot rule
out lower ends PoPs through daybreak. Then as the potential
remaining outflow pushes east later in the morning there may be
enough time for daytime heating to build enough instability to
help reinvigorate  along boundary especially if it interacts
with any out remnant outflows from the Upper Midwest convection
tonight. Given its speed and timing it looks to produced more
scattered showers and few rumbles of thunder late morning into
the early afternoon.

If this late morning activity doesn`t materialize, coverage
remains limited, or pushes out quick enough, then there will be
an increased potential for afternoon showers and storms to
develop. With an environment not as worked over would allow for
instability to build (MUCAPE up to around 1500-2000 J/kg) as
surface dewpoints creep into the mid to upper 60s along with
steeper lapse rates all as a mid-level disturbance treks east
across the region. While deep layer (0-6 km) shear looks meager
only around 30-35 kt, there continues to be a potential to see
a few strong to severe thunderstorms with the later
afternoon/evening round. Main concerns would be damaging winds
and hail. However given 0-1 km storm relative helicity creeping
north of 100 m2/s2 and hints of curved hodograph in the model
sounding, a brief tornado or two cannot be ruled out as well,
especially with the potential for storms interacting with
lingering boundaries from overnight convection. Some models such
as the 00z HRRR show storms developing along a north to south
extent before extending more along a west to east orientation of
a stalling boundary, which could result in training storms,
particularly around the WI/IL border and potential for flooding
concerns.

However, this all remains conditional to how the overnight
upstream convection/MCV evolves and tracks through Monday
morning and if any morning/early afternoon activity
develops/clears the area quick enough. Otherwise, it could end
up just being showers with a few rumbles of thunder limited in
the upscale growth due to lack of thermodynamics developing.

Wagner

&&

.SHORT TERM...
Issued 305 PM CDT Sun Jun 2 2024

Tonight and Monday:

Light winds and high dewpoints may lead to some patchy fog
tonight, but increasing high clouds and slightly increasing
southeast winds through the night should keep widespread dense
fog from developing. Although, river valleys and marshy areas
have a chance at dense fog. Lows should be in the mid 50s east
thanks to lake-cooled air that will spread inland with the lake
breeze this evening. Inland lows will be in the lower 60s where
dewpoints will be higher.

There is still uncertainty about how the radar might look
Monday. The generally thinking is that the thunderstorms
developing in Nebraska this afternoon will evolve into
thunderstorm complex that tracks across Iowa overnight. The
convection with this is expected to diffuse over northern IL
and/or southern WI Monday morning. Meanwhile, a shortwave trough
swinging across the Northern Plains and fueled by the low level
jet overnight should produce scattered thunderstorms that are
also weakening as they reach western WI Monday morning.

Depending on where the boundaries from the overnight convection
stall, and also on how much cloud debris is left over, southern
WI could be the focus for a few areas of thunderstorms by
midday Monday. So we might see some dying showers and perhaps a
rumble of thunder Monday morning, especially west of Madison.
Then any clearing skies will help overcome the cap within our
moist environment in the afternoon and thunderstorms could
freely convect, especially along any remnant boundaries or areas
of convergence. The NAM is showing the potential for 2000 j/kg
of CAPE and bulk shear over 35 kt, which would be sufficient
for severe storms. This is a little overdone due to too high of
dewpoints, but the idea is that we have a chance at severe if
conditions come together just right. The SPC Marginal Risk seems
appropriate at this time.

With precipitable water values of 1.5 to 1.8 inches over our
area by Monday afternoon, heavy rain is a threat with any
clusters of storms that develop.

The precip should be diminishing Monday night, although the GFS
wants to fire convection along a stalled 850mb boundary draped
across southern WI and on the nose of a weak low level jet. This
looks like a less likely scenario at this time.

Cronce

&&

.LONG TERM...
Issued 305 PM CDT Sun Jun 2 2024

Tuesday through Sunday:

There will be two areas of forcing to watch for when predicting
our storm chances on Tuesday. The first one is a forecast storm
complex that will be moving across the mid Mississippi River
Valley Monday night that could lift into southern WI Tuesday
afternoon. The GFS has this idea but the ECMWF and NBM keep
this complex over IL. The other area is vorticity advection
ahead of a stronger shortwave trekking along the US/Canadian
border in the northern Plains.

Warm air advection, moisture advection, and vorticity advection
well out ahead of this upper wave may produce scattered showers
and thunderstorms over southern WI Tuesday afternoon. The high
precipitable water values in the 1.5 to 1.8 inch range will
persist through Wednesday, so heavy rain will continue to be a
threat wherever there is convection. All of this forcing should
keep us fairly cloudy, which will help keep down our instability
and therefore our chance for severe storms.

The Northern Plains upper wave is expected to push through WI
early Wednesday. Gusty northwest winds will usher drier air into
the region. Look for scattered showers during the afternoon due
to steep low level lapse rates with the cyclonic flow aloft.

There is uncertainty about how that upper wave will act over
the Upper Great Lakes after Wednesday. The GFS tries to keep the
closed upper low overhead while the ECMWF moves it to the east
coast. The bottom line is that temperatures will be cooler for
the last half of the week.

Cronce

&&

.AVIATION...
Issued 1010 PM CDT Sun Jun 2 2024

High clouds will spread in overnight with a decaying line of
showers and storms expected across southwestern WI through
daybreak. There will be additional windows for showers and
storms to develop late morning/early afternoon and again later
afternoon/evening along remnant boundaries from upstream
overnight activity. These boundaries may also impact wind
direction causing them to shift with a passage, but generally
expecting southerly winds through much of the day Monday. While
ceilings will generally remain above VFR levels, any
shower/storms would lower ceilings and visibility, but tough to
determine which terminals will be impacted by this activity at
this time. Thus lower flight condition will be possible through
the afternoon and evening, but look to improve overnight as
daytime activity dwindles.

Wagner

&&

.MARINE...
Issued 305 PM CDT Sun Jun 2 2024

Dense fog is possible over the south half of Lake Michigan again
tonight since the dewpoints are in the mid 50s over the
relatively cooler lake water. Look for light and variable winds
to increase out of the southeast Monday. Storms are possible
Monday afternoon and evening, and at times through Wednesday
morning.

Light winds will persist through Wednesday morning. Look for
gusty northwest winds in the wake of a cold front Wednesday
afternoon. Gusts may exceed Small Craft Advisory levels near the
lakeshore during this time.

Cronce

&&

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

$$

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