992
FXUS63 KMKX 212135
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
435 PM CDT Fri Jun 21 2024

.KEY MESSAGES...


-  Flood Watch continues for flash flooding potential for
   portions of south central and southeast WI continues through
   Saturday evening. Multiple rounds of showers and storms are
   expected with rainfall amounts between 1-3 inches and locally
   higher amounts exceeding 2 inches, especially for areas west
   of I39/90 corridor.

-  Could see a stronger thunderstorm or two later this
   afternoon and evening with gusty winds. However, there will
   be a better potential for stronger to severe thunderstorms
   Saturday afternoon/evening (risk 2 out of 5). With any
   thunderstorms damaging winds will be the main hazard, but
   large hail and an isolated tornado is not out of the
   question.

-  Heat indices will climb back into the upper 80s to mid 90s
   Friday and again Saturday, especially for inland areas along
   and south of I- 94/HWY-18.

&&

.SHORT TERM...
Issued 427 PM CDT Fri Jun 21 2024

Tonight through Saturday night:

The outflow boundary from upstream convection this morning continues
to be focus for shower and thunderstorm development this afternoon,
especially as it interacts with the effective warm front which is
strung across east central WI. While most storms have been
brief as they are struggling to maintain their longevity given
meager shear (<30 knot), any interactions with nearby storms and
any boundaries can help maintain these storms a bit longer
especially as the airmass destabilized and SBCAPE has climbed to
around 1000-2000 J/kg. Any of this type of activity can result
in localized gusty winds, but more likely resulting in heavy
rainfall given the slow movement. Localized flash and/or river
flooding will be possible with any storms lingering or moving
over the same area for extended period of times through the
evening. Overall, the higher shower and thunderstorm potential
through this evening will be for areas along and north of
Highway-151, while areas south-southeast will be more scattered
activity this evening. However, areas closer to Lake Michigan
are behind a lake breeze and with the more stale marine
environment will have a lesser threat for thunderstorms.

Will continue to see shower and storms overnight linger along the
boundary, but thinking the scattered cover will decrease
overnight. Some CAMs have a round of showers and storm moves
through early in the morning and clearing out just mid morning.
With the warm front lingering across the northern tier of the
CWA and morning activity moving out, the late morning/afternoon
should have enough time to recover and destabilized before
Saturday afternoon activity develops and swings across the area.

Saturday afternoon and evening holds the better potential for more
scattered strong to severe thunderstorm potential. Upper-level
dynamics align over the region favoring thunderstorm
development given a strengthening +40 knot LLJ and shortwave
trough aligning with the cold frontal passage. PWATs look to be
around 1.5-2.0 inches and given hi-res CAMs and HREF ping SBCAPE
1500-2000 J/kg the environment will be conducive for
thunderstorm development. However, with deterministic progging
deep layer (0-6km) between 30-40 knots, it will be enough to
maintain thunderstorms upscale growth. Most CAMs agree on this
activity Saturday afternoon/evening growing into more of a
linear feature ahead of the cold front. However, cannot rule out
an isolated storm our two to develop ahead of the main line
across the warm sector, especially with any lingering
outflow/mesoscale boundaries from convection earlier in the day.
Additional HRRR model sounding hodographs do show some decent
low- level (0-3km) SRH 100-150 m2/s2, so low-end isolated
tornadoes threat cannot be ruled out if anything develops.
Otherwise, while cannot rule out a embedded tornado within the
linear mode especially with any bowing/surges, the chances are
low given shear vectors are more parallel to the line. Thus the
main concern will be damaging winds as the line pushes through.

One caveat to the severe potential for Saturday will be where the
warm front boundary ends up by by the afternoon. The 12z models
favored it more across central WI, while the 18z has trended it
a bit further south. Thus if the southern trend continues it
may pull the severe threat south with it. Nevertheless, the
potential remains for a line of severe thunderstorms to work
their way across southern WI Saturday afternoon and evening
bring damaging winds and heavy rainfall/flooding threat along
with a non-zero isolated tornado threat.

Otherwise, areas south of the warm front will see temps warm back
into mid to upper 80s with heat indices in the low to mid 90s.
However, expect it to be cooler north of wherever the front sets up
and for areas along the lakeshore.

Wagner

&&

.LONG TERM...
Issued 427 PM CDT Fri Jun 21 2024

Sunday through Friday:

Sunday should be a pleasant day with highs near 80 and lower
humidity. Short waves will impact the area late Sun/Sun night and
Tue/Tue night. A weak cold front will pass through the area
late Sun/Sun night. FROPA is expected to be dry at this time. If
there were to be precip with this FROPA, E cntrl WI would be
favored. The next short wave is due in for Tue PM/Tue night
which will be responsible for the next chance of rain (30%-50%)
late Mon night through Tue night. NW upper level flow will keep
things dry through the end of the period as a 1020 mb SFC ridge
moves across WI Thu.

BM


&&

.AVIATION...
Issued 427 PM CDT Fri Jun 21 2024

Additional development ongoing across southern WI as outflow
boundaries make there way across the area. Shower and storm
this afternoon afternoon will bring heavy rainfall reducing
flight conditions. Also cannot rule out a stronger storm or two
this afternoon and evening with gusty winds being the main
concern. Additional shower and thunderstorm activity expected
overnight in Saturday.

Wagner

&&

.MARINE...
Issued 427 PM CDT Fri Jun 21 2024

Expect light northerly winds over Lake Michigan today as high
pressure weakens over Lake Superior. Light northeast winds this
evening will then shift to modest southerly over the southern half
of the lake as a warm front moves northward. The warm front and
southerly winds will then extend into the northern portion of the
lake for Saturday followed by low pressure tracking east
across central Lake Michigan early Saturday evening. A cold
front will quickly follow with modest northwest winds over the
entire lake for Sunday. Rounds of thunderstorms are expected
across the lake at times from this afternoon into Saturday
night.

Wagner

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-WIZ058-
     WIZ059-WIZ062-WIZ063-WIZ064-WIZ065-WIZ067-WIZ068-WIZ069
     until 7 PM Saturday.

LM...None.
&&

$$

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