217
FXUS63 KMKX 030223 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
923 PM CDT Tue Jul 2 2024

.KEY MESSAGES...

- Showers and some thunderstorms will continue to move across
  the area this evening, before exiting overnight. Locally heavy
  rainfall and flooding are the main concerns in this activity.
  A Flood Watch remains in effect until 1 AM CDT Wednesday
  across areas around and southwest of Madison.

- Dangerous swimming conditions continue until 1 AM CDT
  Wednesday at Lake Michigan beaches in Sheboygan and Ozaukee
  Counties.

- Elevated water levels continue on area rivers and streams
  through the end of the week. Flood Warnings remain in effect
  in several locations.

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

&&

.UPDATE...
Issued 923 PM CDT Tue Jul 2 2024

Showers and some thunderstorms will continue to move east across
the area late this evening, before exiting from west to east
overnight, along and ahead of a cold front. Upper divergence
from the right entrance region of a jet streak should move away
from the area, so the current activity may gradually weaken as
it continues east.

Still concern for locally heavy rainfall and localized
flooding, with high precipitable water values over 2.00 inches
and moist adiabatic temperature and moisture profiles. Rainfall
rates of 1 to 1.50 inches per hour have been seen in earlier
convection, though these rates may lower as upward vertical
motion gradually weakens overnight.

For now, will maintain the Flood Watch for Madison and to the
southwest, until all of the moderate rainfall moves out of that
area. May see some rivers rise in response to this latest round
of rainfall.

The high swim risk and Beach Hazards Statement continues for
Lake Michigan beaches in Sheboygan and Ozaukee Counties until 1
AM CDT, with southeast winds bringing high waves and rip
currents to that area.

Wood

&&

.SHORT TERM...
Issued 331 PM CDT Tue Jul 2 2024

Tonight and Wednesday:

Synopsis/Mesoanalysis: Afternoon surface observations depict a cold
front extending from the MN Boundary Waters south into the Missouri
Valley. Evident in GOES water vapor imagery, an upper shortwave is
progressing eastward along the South Dakota-Nebraska border. Both of
the aforementioned features are progged to track east toward the
region this evening, triggering shower and thunderstorm development
in the process. Locally heavy rainfall and flooding are possible in
this activity given an unseasonably moist air mass in place across
the area, with a Flood Watch in effect across our southwestern
counties between 3 PM and 1 AM. Convection will push east of the
area during the predawn hours as the aforementioned cold front
clears the area from west to east. Post-frontal high pressure will
nudge into southern Wisconsin Wednesday afternoon, allowing for
decreasing cloud cover and primarily dry conditions.

Rest Of This Afternoon & This Evening: Hazardous swimming
conditions continue at all Lake Michigan beaches given a
combination of high waves and dangerous currents. Already in
progress to our west, shower and thunderstorms will continue to
fill in as they move toward the area. Storms will be
encountering an unseasonably moist air mass characterized by
precipitable water values in the 1.75 to 2.25 inch range, which
reside anywhere between 1.5 and 2 standard deviations above
early July normals. Storms will thus be capable of producing
heavy rainfall rates this afternoon/evening, and will pose some
potential for flooding. Latest flash flood guidance from the
North Central River Forecast Center depicts six hourly values
between 1.5 and 2 inches across the region. 6 hour QPF progs
from the 12Z HREF, in addition to more recent runs from the
HRRR, point toward these thresholds being met in localized
pockets across southwestern Wisconsin and the Wisconsin River
Valley. Have thus issued a Flood Watch for Sauk, Columbia, Iowa,
Dane, Lafayette, and Green Counties between 3 PM and 1 AM. Stay
aware for rising water in these locations, and remember to turn
around, don`t drown if encountering flooded roadways. While
well secondary to the flooding potential, an isolated strong to
severe storm can`t be completely ruled out over far southwestern
counties (particularly Green, Iowa, and Lafayette Cos) during
the 4-8 PM timeframe. This potential will be heavily contingent
upon the realization of surface-based instability. Said
realization has been hinted in the 12Z HREF, as well as more
recent runs of the HRRR and NAM Nest. Damaging winds would be
the primary concern in any strong/severe storms, though a brief
tornado would be possible in any activity becoming favorably
aligned with 40-45 kt, southwesterly shear vectors in the 0-3 km
layer. Will continue to monitor trends through the remainder of
the afternoon and evening hours.

Wednesday: Skies will turn partly cloudy by late morning as the cold
front pushes east of the area. Have maintained an entirely dry
forecast, but did insert some 10% precip probs over far northern
counties, where some mesoscale guidance hints at isolated shower and
thundershower development during the afternoon hours.

&&

.LONG TERM...
Issued 331 PM CDT Tue Jul 2 2024

Wednesday night through Tuesday:

This will be an active period with shortwave troughs arriving
within wnwly flow aloft. For Independence Day, a 700 mb shortwave
trough will track across nrn IL or far srn WI. Mid level warm,
moist advection and PVA along with marginal CAPE will support
PoPs of 20-40 percent for the afternoon and evening. The
convection may only be elevated and will depend on the amount of
clouds and sfc heating. Either way, scattered showers and isold
storms are forecast.

A larger and slower moving shortwave trough will then approach
from the ern Dakotas and MN late Thu nt. A surge of 850-700 mb
warm, moist advection and increasing PVA within a PW airmass of
1.4-1.8 inches and marginal CAPE will result in widespread showers
and sct storm development. A developing sfc low will move across
srn WI during the day on Fri while the upper low moves across
central to ne WI. Widespread showers and possibly some heavy
rainfall will continue at least in the morning. Some showers may
linger into Fri nt, but shortwave ridging and a pleasant day is
expected for Sat.

A series of shortwave troughs will continue to affect the region
from Sun-Tue with chances for showers and storms each day. Temps
during the extended will be near normal but below normal on Fri
given the widespread clouds and showers.

Gehring

&&

.AVIATION...
Issued 923 PM CDT Tue Jul 2 2024

Showers and some thunderstorms will continue to move east across
the area late this evening, before exiting from west to east
overnight, along and ahead of a cold front. The current
activity may gradually weaken as it continues east. Still
concern for locally heavy rainfall and localized flooding,
mainly around and southwest of Madison.

Ceilings will drop gradually overnight into Wednesday morning,
with a period of 700 to 900 foot AGL ceilings. May also see some
locally reduced visibility values to 1 to 2 miles in any
heavier rain areas. The low clouds should move out or scatter
out across the area by middle to late morning on Wednesday.
Scattered diurnal cumulus clouds may develop in the afternoon.

Light winds will gradually shift southwest to west overnight.
Low level wind shear conditions are expected overnight, ending
around 09Z to 10Z Wednesday, with south southwest winds around
40 to 45 knots. West winds will linger into Wednesday, with a
few gusts to 15 knots or so in the afternoon.

Wood

&&

.MARINE...
Issued 923 PM CDT Tue Jul 2 2024

A cold front will continue to move across Lake Michigan
overnight. Showers and thunderstorms are expected to continue
until the front passes through. Breezy southeast to south winds
will gradually veer southwest behind the front overnight into
early Wednesday morning, with southwest to west winds later on
Wednesday.

A Small Craft Advisory remains in effect until 1 AM CDT
Wednesday for areas north of Port Washington, for gusty
southeast to south winds and lingering high waves.

Winds will weaken Wednesday night into Independence Day, as
high pressure around 30.0 inches moves into the area. Low
pressure around 29.7 inches will then move into the region
Friday, then slowly east Friday night. Easterly winds ahead of
the low Friday should gradually shift westerly behind it Friday
night into Saturday.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ056-WIZ057-WIZ062-WIZ063-WIZ067-WIZ068 until
     1 AM Wednesday.

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

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

&&

$$

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