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000
FXUS63 KMKX 170322
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1022 PM CDT Tue Apr 16 2024

.KEY MESSAGES...

- Additional rounds of showers and thunderstorms will continue
  tonight and chances will linger through Wednesday. May see
  gusty winds and small hail along with ponding and minor
  flooding for low-lying areas from heavier rainfall.

- May see rises on area rivers due to heavy rainfall overnight.

&&

.UPDATE...
Issued 1020 PM CDT Tue Apr 16 2024

Line of showers and thunderstorms continue to work their way
across southern WI late this evening and should push out over
the lake around midnight. While some showers may be able to mix
down some gusty winds aloft, severe threat has diminished as the
the storms outran the favorable instability and higher dewpoints
of the warm sector. May still see a few small pockets of hail,
but otherwise, mainly thinking the severe threat is over for the
night. However, heavy rainfall may result in localized
ponding/minor flooding of low-lying areas, especially if any
storms train over the same area. This can also result in
additional rises on area rivers.

Otherwise, there will be another chance to see some additional
shower/storm activity in the morning as the occluded front
swings through the region, but not expecting this activity to be
as strong as storms this evening.

Wagner

&&

.SHORT TERM...
Issued 319PM CDT Tue Apr 16 2024

Tonight through Wednesday night:

As the low pressure system in Iowa continues to advect northeast
toward central Wisconsin today there will be showers and storms
moving through the area. The line of thunderstorms in Iowa and
Minnesota is just ahead of the main surface boundary. There is
development behind this line along the boundary, which is where
you can see more supercellular type convection firing.
Rain/storms will pick up this afternoon as this sfc boundary and
upper level support from the low moves into the area. The LLJ
will be ramping up a bit during this time as well. Given this,
the shear will be pretty impressive across southwestern
Wisconsin. The 0-6km shear is going to be pushing 60kts at times
as this boundary begins to move through.

Now for this afternoon/evening the convection out ahead of this
frontal boundary will be moving in first and will be a bit
separated from the better dewpoints (moisture), and shear. The
distance from this boundary will limit the ability for any of
this convection to be surface based which is what we will need
for any tornadic activity here. So while the chance for
tornadoes in southwestern Wisconsin is non-zero it is still very
conditional. The conditional nature is based on how far north
the warm sector can get to make storms surface based. Hail and
strong winds will be the primary threat. As storms move
northeast away from the better support toward Lake Michigan,
the severe potential is expected to decrease.

The main period of convection should end by around midnight
tonight. Dry conditions will be likely(~70%) during the late
night hours, this will be caused by the dry slot moving through
the area. Around daybreak showers and storms are expected to
return as the occluded front moves through. The severe threat
with this morning convection will be very marginal. Storms are
expected to develop overhead and move northeast. From the CAMs
the NAM and NAMnest seem to be the most aggressive with this
convection. Every other short term guidance is much more relaxed
with development. There will be a short window (roughly 2 hours)
where there could be some lingering CAPE. This CAPE is what we
will need to get any stronger storms Wednesday morning with this
broken line that is expected to develop. The chances for any
stronger convection tomorrow morning is expected to be around
25%. By Wednesday evening drier conditions are expected to
return as the low pressure system begins to pull out of the
state.

Not much has changed in the realm of hydro concerns for this
event. Widespread 0.75 to 1.25 inches are expected from this
afternoon through Wednesday evening. A few locations could see
totals as high as 2 inches, particularly across southwestern
Wisconsin. A few rivers in the western parts of the CWA will
likely (~70%) be impact and that will be the main item to watch
when it comes to hydro concerns. Rainfall rates will be the
secondary item to keep track of as any heavy rainfall could
result in minor Urban effects. Overall flash flooding is not
expected at this time.

Patterson

&&

.LONG TERM...
Issued 319PM CDT Tue Apr 16 2024

Thursday through Tuesday:

850 to 700 mb WAA is expected over the region on Thursday as a
weakening surface low passes over the middle Mississippi Valley.
Light to moderate rain spurred by this warm advection is expected
on and off through the daytime hours on Thursday. WAA should exit
east in the evening, and rain will gradually move out with it.
Weak cold advection will then kick in on northwest winds overnight
into early Friday morning.

By Friday, a high pressure ridge will pass overhead leading to
clear skies, but cooler conditions amid the cold air advection. A
strong low level jet is expected to round the base of a large
area of low pressure over centered over eastern Canada and pass
over the upper Great Lakes region. With our sunny skies, we should
be able to mix up to the stronger winds aloft and bring this
momentum down to the surface, causing gusty west surface winds.
Winds will die down Friday evening as mixing ceases and the LLJ
pulls east of the area.

High pressure should then persist into the weekend, keeping things
dry amid cooler temperatures.

CMiller

&&

.AVIATION...
Issued 1020 PM CDT Tue Apr 16 2024

Line of showers and thunderstorms continue to work their way
across southern WI this evening. Eastern terminals will see a
few hour window through 06z for this activity bringing lower
visibilities and potentially lower ceilings, but trends have
kept ceilings above VFR mostly. Meanwhile western terminals will
see some lingering shower activity before drying out. Most
upstream trends keep ceilings above VFR, but given the
increased moisture could see ceilings lower through early
Wednesday morning as the low lifts across WI. Could see another
round of showers along with lower flight conditions Wednesday
morning as the occluded front swings through the area.
Otherwise, expect gusty southeasterly to continue tonight before
turning more westerly through Wednesday morning.

Wagner

&&

.MARINE...
Issued 319PM CDT Tue Apr 16 2024

The gusty east winds today will persist as the low pressure
system continues its approach toward central Wisconsin. Gales
will be possible at times across Lake Michigan, thus a Gale
Warning is in effect. This Gale Warning has segmented the lake
into thirds with each grouping of zones starting at the same
time, but ending from south to north overtime. The far northern
portions of the lake will have the Gale Warning in effect
through Wednesday evening. As winds diminish they will turn
become southwest to westerly with the wind shift occuring over
the southern and central portions of the lake first. Westerly winds
will then continue Thursday morning before becoming
southwesterly by Thursday afternoon for the entire lake as the
low departs the area.A Small Craft will likely be needed for
parts of the nearshore following the end of the Gale Warning for
a least a short period.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-LMZ643-
     LMZ669-LMZ671-LMZ868-LMZ870-LMZ872 until 7 AM Wednesday.

     Gale Warning...LMZ080-LMZ644-LMZ645-LMZ646-LMZ673-LMZ675-
     LMZ777-LMZ779-LMZ874-LMZ876-LMZ878 until 1 AM Wednesday.

     Gale Warning...LMZ261-LMZ362 until 7 PM Wednesday.

&&

$$

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