436
FXUS63 KMKX 021632
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1132 AM CDT Tue Jul 2 2024

.KEY MESSAGES...

- Rainfall is pushing across eastern areas late this morning.
  Additional shower and storm development is expected this
  afternoon and evening. Primary concern is heavy rainfall,
  especially tonight. An isolated strong to severe storm is
  possible over far southwestern counties.

- River flooding and high water levels continue this week.
  Additional rises will be possible with any heavier rainfall
  that occurs through Tuesday night.

- Independence Day forecast trends for widespread showers and
  thunderstorms continue to push later overnight Thursday into
  Friday. However still will be a 20-40% chance for spotty
  showers and thunderstorms with lightning through Thursday
  afternoon/evening.

&&

.UPDATE...
Issued 1059 AM CDT Tue Jul 2 2024

Linked to a shortwave trough progressing overhead, an area of
rain showers is pushing east toward the Lake Michigan shoreline
late this morning. Affiliated with a broad regime of 925 mb WAA,
an area of scattered shower/thundershower activity is in
progress over northeastern Iowa. Expect that some of this
activity could push into southwestern zones through early
afternoon, when more widespread showers and storms will develop
over Iowa and northern Missouri. This activity will quickly
organize into a line as it moves east, with storm coverage
gradually expanding northward as a second upper wave & low
level jet dynamics move in from the west late this afternoon and
evening. The northern end of this convection is progged to
cross the area during the 3PM-1AM timeframe, moving out over
Lake Michigan during the predawn hours. Continue to reflect this
trend in the PoP and weather grids.

A very moist environment will be in place ahead of the
afternoon/evening convection. Precipitable water values at and
above 2 inches -- anywhere between 1.5 and 2.5 standard
deviations above early July climatology -- will advect into the
region as the low level jet ramps up, creating an environment
conducive for heavy rainfall rates within this
afternoon/evening`s thunderstorms. Latest flash flood guidance
from the North Central River Forecast Center shows six hourly
values between 1.50-2.50" across the region. Despite a dynamic
synoptic environment & anticipated progressive storm motions,
QPF forecasts from the 12Z CAM suite indicate that said
thresholds could be met in pockets of southwestern Wisconsin and
the Wisconsin River Valley. In coordination with neighboring
offices, have thus issued a Flood Watch for Sauk, Columbia,
Iowa, Dane, Lafayette, and Green Counties between 3PM this
afternoon and 1 AM Wednesday.

While hydro is far and away the main concern in this afternoon`s
convection, we`ll be closely monitoring areas southwest of
Madison for isolated severe potential. This potential will be
contingent upon a warm sector currently over Iowa nudging into
these zones. 12Z CAM runs, as well as consecutive more recent
runs of the HRRR, depict the northeastern edge of said warm
sector building into Iowa-Lafayette-Green counties by late
afternoon. If these solutions verify, a brief window of severe
potential would exist in these zones between primarily 3 and 6
PM. Will continue to monitor trends given this afternoon`s
convection through the coming hours.

Quigley

&&

.SHORT TERM...
Issued 359 AM CDT Tue Jul 2 2024

Today through Wednesday:

Showers and storms early this morning are firing along a surge
of WAA and some mid level frontogenesis. The LLJ is just off to
our west in Iowa and far western Wisconsin this morning which is
where the main area of rain and thunderstorms is located. This
main area of rain/storms will be producing some heavier rainfall
in comparison to what we are seeing here in southern Wisconsin.
Light to moderate rain is expected to gradually move through
this morning pulling out of the forecast area by late this
morning. As these showers moved east they have continued to
fight dry air. Dry air in the low to mid level has caused
showers to become scattered to isolated across far southern and
southeastern Wisconsin. It is likely that some rain will
struggle to reach the ground in those areas until the air
column can become fully saturated. With the ongoing WAA this is
only a matter of time.

As the morning showers and storms pull out of the state later
this morning, a lull in the precipitation is expected. This lull
is expected to start late this morning and persist into the
afternoon hours. Late this afternoon into the evening additional
rain showers will move in from the west. These showers are
expected to be focused along the lead edge of the LLJ and along
the cold front. PWATs will be high (around 2 inches) during
this time which will result in heavy rainfall. There is a
concern for training thunderstorms this afternoon with the slow
moving nature of the cold front and LLJ. With the upper level
jet expected to be overhead during this time, storms could grow
in height and bring some heavy downpours. Southwestern and west
central Wisconsin will have the best potential for rainfall
totals over 2 inches as this system moves through. Keeping a
close eye on the rain early this morning (especially to the
west of our forecast area) as rainfall amounts may overachieve
and lead to growing flooding concerns. Rainfall totals to our
west will highlight the potential for heavy rain for our area
later this afternoon and evening depending on how this system
performs could lead to a potential flood watch for southern
Wisconsin later today.

The severe weather potential will be low (marginal) today
across southern Wisconsin. This is in part due to the fact that
CAPE will be lacking. Skies are expected to stay overcast which
will limit the ability for instability to grow. Any clearing
would help with SBCAPE. Regardless the CAPE profiles are very
long and skinny which doesn`t bode well for strong to severe
storms. Any wet microburst activity isnt out of the question if
a storm gets particularly tall, same goes for small hail.
Flooding is the main concern today.

There is a high swim risk today for all Lake Michigan beaches
due to building waves from the onshore breezy winds. With wind
gusts to 30 mph expected throughout the day waves are expected
to climb to 3-5 feet or greater. Dangerous currents such as
structural and rip currents are possible. The high swim risk
will persist across Sheboygan and Ozaukee Counties through
tonight. Stay out of the water during this time.

Patterson

&&

.LONG TERM...
Issued 359 AM CDT Tue Jul 2 2024

Wednesday night through Monday:

Weak surface high pressure will continue to push east overnight
Wednesday into Thursday morning. Most medium range model guidance
supports the drier trend through the morning of July 4th and even
into the the afternoon. Thus PoPs are lowering for the first part
of the day. Then there are hints of a mid-level ripple of
vorticity to quickly trek across the region through the
afternoon/early evening hours. Paired with a surface warm front
lifting into the area along with increasing PWATs to around 1.5
inches, cannot rule out some spotty showers/thunderstorms for the
second half of the day. At this time this activity does not look
be a wash out, especially given the potential to battle some
lingering dry air and the more favorable upper-level dynamics
remaining further upstream. Nevertheless given the increased
outdoor festivities for Independence Day holiday, a low-end
(<40%) potential remains and cannot rule out some minor impacts
(mainly lightning) for these events through the early evening
hours if anything shall develop.

Given the latest 00z model trends, the better chances to see more
widespread showers and thunderstorms look to be overnight
Thursday after 06z (1 AM CDT) into Friday as the mid-level
shortwave trough axis pushes east. The associated surface low
looks to lift into the region around the same time and trends show
the low meandering over WI through the day Friday as it occludes.
Given the slower movement of this system, shower chances linger
through much of the day Friday. NBM does show some instability
(SBCAPE <500 J/kg) as the low works its way across the region for
Friday, but GFS and ECMWF are not as aggressive, but still would
be able to see some thunderstorms with this activity for Friday.

Otherwise, this system is progged to push out of the area for
Saturday with high pressure and upper-level ridge building behind
it. Thinking Saturday will remain mostly dry given the drier
airmass and subsidence expected over the area. However could see
another round of showers and storms for the later half of the
weekend into early next week as a system treks across the Upper
Midwest.

Wagner

&&

.AVIATION...
Issued 1059 AM CDT Tue Jul 2 2024

Additional shower and thunderstorm development is anticipated to
our west this afternoon, tracking across southern Wisconsin
terminals during the late afternoon and evening hours. VIS &
attendant categorical reductions are likely in this activity,
and have been accounted for in the 15Z TAF update. Precip should
push east during the predawn hours Wednesday, with VFR
conditions becoming established by the second half of the
morning hours. Increasing low level winds will create some
potential for LLWS this evening. Currently monitoring trends,
with mentions possible in coming updates.

Quigley

&&

.MARINE...
Issued 359 AM CDT Tue Jul 2 2024

South to southeast winds will persist across Lake Michigan into
tonight. Winds will increase becoming breezy later this morning
with gusts of 25-30 kts expected. A Small Craft Advisory is in
effect this morning into tonight due to the breezy winds.
Overnight tonight into Wednesday morning a cold front will move
across the lake bringing rain, thunderstorms and westerly winds.
West to southwest winds are expected through Wednesday. Weak
high pressure returns to the region Wednesday night into
THursday bringing a return of light and variable winds.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ056-WIZ057-WIZ062-WIZ063-WIZ067-WIZ068...3 PM
     Tuesday to 1 AM Wednesday.

     Beach Hazards Statement...WIZ052-WIZ060 until 1 AM Wednesday.

     Beach Hazards Statement...WIZ066-WIZ071-WIZ072 until 7 PM
     Tuesday.

LM...Small Craft Advisory...LMZ643 until 1 AM Wednesday.

     Small Craft Advisory...LMZ644-LMZ645-LMZ646 until 7 PM Tuesday.

&&

$$

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