566
FXUS63 KMKX 271908
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
208 PM CDT Sat Apr 27 2024

.KEY MESSAGES...

- Scattered storms are still expected to develop along a weak
  cold front late this afternoon and evening. A few of these
  storms may become severe with large hail and damaging winds,
  but cannot rule out a tornado or two.

- Rounds of showers and storms are expected from this evening
  through late Sun nt. The flash flood threat will remain low
  but local urban and small stream flooding is more probable.

&&

.UPDATE...
Issued 107 PM CDT Sat Apr 27 2024

A Wind Advisory has been issued for east central and far ern WI
as the LLJ has been slow to exit. A weakening trend in the
pressure and wind fields is expected by late this afternoon.

Cumulus to cumulus congestus are lined up along and east of a
weak cold front over ern IA to sw WI and the Madison area. Brief
convection has been occurring over ern IA into nw IL early this
afternoon. Despite shortwave ridging aloft and weakening
pressure and wind fields into this evening, the CAMs and current
activity suggest convective initiation will occur along the
front from mid to late afternoon and evening. MLCAPE will range
from 1500-2000 J/kg with effective shear of 30-40 kts during
this time. The 0-3 KM hodographs remain fairly straight for any
cells on the front but some 0-1 KM clockwise turning is observed
east of the front. Thus a small tornado threat remains with
better probs for large hail and strong wind gusts. Since the
deep layer shear is parallel to the front, a broken line of
storms may seed each other resulting in greater pcpn efficiency
and a more solid line of storms. At this time the QLCS threat
is low as 0-3 km shear is parallel to the front and weakening
into the evening. For late evening into the overnight it is
possible an area of convection approaching from IA could clip
srn WI


Gehring

&&

.SHORT TERM...
Issued 415 AM CDT Sat Apr 27 2024

Today through Sunday:

Early today: Except for a band of light rainshowers currently
passing close to Sauk and Marquette counties, dry weather is
expected to prevail until this afternoon, with gusty southwest
winds rapidly building after sunrise. The strongest wind gusts
are expected near Sheboygan and Fond du Lac counties, upwards of
40 mph. Roughly 30 to 40 mph gusts elsewhere.
Low pressure around 29.5 inches over northwest Wisconsin will
continue to gradually weaken as it moves northeast across Lake
Superior into Ontario this afternoon. Gusty south winds are
expected across Lake Michigan today, with a few gusts approaching
or reaching gale force, especially in the northeast portion of
the lake.

Winds will then gradually shift from southwest to northerly
tonight as a cold front tracks south, but southerly winds will
continue over far southern Lake Michigan as the front stalls.
Brisk northeast winds will then prevail over central Lake Michigan
on Sunday with lighter winds in the north, and variable winds in
the south where the stalled front remains. Modest east to
southeast winds will then develop over all of the lake Sunday
night as the stalled front moves north as a warm front. Brisk east
winds, possibly reaching gale force, are expected over the
northern tip of the lake late Sunday night into Monday morning.
Breezy south winds will develop over the remainder of the lake on
Monday.

Rounds of showers and thunderstorms are expected tonight into
Monday morning. A few of these storms could produce locally gusty
winds and hail.
This afternoon / evening: Storms are expected to develop along a
southwest to northeast oriented frontal boundary, perhaps as
early as 1 PM or as late as 7 PM today. CAMs currently depict
the position of convective initiation as a line from Monroe WI
to Sheboygan WI, with roughly one or two counties distance
east/west disagreement in positioning. Forecast soundings
indicate southwest winds throughout the column, with
unidirectional shear, yet impressive helicity integrals. HREF
Mean MUCAPE south of the boundary exceeds 2000 j/kg, with a
surface-based effective inflow layer. HREF mean STP exceeds 2.0,
with some models (esp. the Nam NEST) pushing 3.0. This
parameter space would suggest an environment capable of all SVR
hazards (hail, damaging winds, and possibly tornados). Localized
heavy rainfall is a concern, especially if storms along the
front affect the same area multiple times. The best agreement in
model QPF is positioned along and south / southwest of the I-94
corridor.

Late tonight through Sunday: Instability is progged to decline
late tonight. Some models depict a lull in shower / storm
activity late tonight, while others depict wider storm coverage
with weaker intensity. Severe wx potential does continue into
Sunday, but with HREF mean MUCAPE less than 1000 j/kg (even with
the compliment of daytime heating), this is looking like the
less active day of the two. That said, the positioning of the
warm front leaves much in question in the way of instability.
Regardless of severe wx potential, localized heavy rainfall
seems equally probable on Sunday, with model QPF evenly split
between the two rounds of activity.

Sheppard

&&

.LONG TERM...
Issued 415 AM CDT Sat Apr 27 2024

Sunday night through Friday:

Synopsis: The upper trough ejecting into the Northern Plains on
Sunday afternoon/the conclusion of the short term period will
progress toward the Canadian bLow pressure around 29.5 inches over
northwest Wisconsin will continue to gradually weaken as it
moves northeast across Lake Superior into Ontario this
afternoon. Gusty south winds are expected across Lake Michigan
today, with a few gusts approaching or reaching gale force,
especially in the northeast portion of the lake.

Winds will then gradually shift from southwest to northerly
tonight as a cold front tracks south, but southerly winds will
continue over far southern Lake Michigan as the front stalls.
Brisk northeast winds will then prevail over central Lake Michigan
on Sunday with lighter winds in the north, and variable winds in
the south where the stalled front remains. Modest east to
southeast winds will then develop over all of the lake Sunday
night as the stalled front moves north as a warm front. Brisk east
winds, possibly reaching gale force, are expected over the
northern tip of the lake late Sunday night into Monday morning.
Breezy south winds will develop over the remainder of the lake on
Monday.

Rounds of showers and thunderstorms are expected tonight into
Monday morning. A few of these storms could produce locally gusty
winds and hail.order Sunday night into early Monday morning.
The advancement of the upper wave will support surface low
placement along the MN-WI border vicinity by sunrise Monday,
with a cold front forecast to be extending southwest into the
Central Plains. The upper trough will progress across Lake
Superior during the day on Monday, gaining separation from its
attendant surface cyclone in the process. This will promote
gradual filling of the surface low over northern WI and the
Upper Peninsula of MI Monday afternoon, with the associated cold
front crossing & ultimately exiting the region during the
evening hours. The advancing upper wave & surface front will
support additional periods of showers and embedded thunderstorms
from Sunday night through Monday afternoon. Westerly surface
flow will usher a drier/Canadian air mass into the state Monday
night, with winds quickly turning back out of the south from
Tuesday into the middle portions of next week. Occurring in
response to an upper jet/trough pairing approaching from the
Northern Plains, said southerly flow will allow moisture to
return to the area on Tuesday afternoon. Additional showers and
storms will be possible Tuesday night through Wednesday as a
surface low related to the upper trough/jet tracks across
Ontario & pulls a cold front across the state. The boundary is
likely to stall out somewhere to our south & east during the
Thursday/Friday timeframe, with considerable spread in placement
evident in current deterministic & ensemble-based guidance.

Sunday Night & Monday: Anticipate periods of showers and embedded
thunderstorms. While depicting plenty of shear through the column,
available forecast soundings show only weak (<500 J/kg) MUCAPE
through the majority of this timeframe, suggesting low overall
strong/severe storm potential in this activity. Will nevertheless
monitor trends over the coming cycles, as a slower FROPA on Monday
PM would allow for instability & isolated strong/severe potential to
trend up.

Tuesday Night & Wednesday: Expect another round of rainfall during
this portion of the period. Early progs show some signal for CAPE to
work into the area, which has justified continued mentions of
thunder in the overnight weather grids. It remains too early to
comment on any stronger storm potential, though trends will
continue to be monitored.

Thursday & Friday: Forecast uncertainty jumps up considerably during
this portion of the period, as area weather is likely to be
influenced by where the mid-week frontal boundary ultimately stalls.
Additional rainfall chances would be possible in the scenario that
the feature lingers further north than currently progged. Will
continue to adjust the late week forecast as boundary placement
clarifies.

Quigley

&&Low pressure around 29.5 inches over northwest Wisconsin will
continue to gradually weaken as it moves northeast across Lake
Superior into Ontario this afternoon. Gusty south winds are
expected across Lake Michigan today, with a few gusts approaching
or reaching gale force, especially in the northeast portion of
the lake.

Winds will then gradually shift from southwest to northerly
tonight as a cold front tracks south, but southerly winds will
continue over far southern Lake Michigan as the front stalls.
Brisk northeast winds will then prevail over central Lake Michigan
on Sunday with lighter winds in the north, and variable winds in
the south where the stalled front remains. Modest east to
southeast winds will then develop over all of the lake Sunday
night as the stalled front moves north as a warm front. Brisk east
winds, possibly reaching gale force, are expected over the
northern tip of the lake late Sunday night into Monday morning.
Breezy south winds will develop over the remainder of the lake on
Monday.

Rounds of showers and thunderstorms are expected tonight into
Monday morning. A few of these storms could produce locally gusty
winds and hail.

.AVIATION...
Issued 120 PM CDT Sat Apr 27 2024

Sct-bkn035-045 cumulus and cumulus congestus this afternoon and
evening with scattered to numerous storms developing over srn
WI. The passage of a cold front late tonight will then result in
a moist enely flow and low stratus development. MVFR Cigs will
develop by early morning Sunday then fall below 1 kft for the
remainder of the day. Some fog development will also occur
during this time. Rounds of showers and storms will also
continue on Sunday.

Gehring

&&

.MARINE...
Issued 120 PM CDT Sat Apr 27 2024

Low pressure around 29.5 inches over northwest Wisconsin will
continue to gradually weaken as it moves northeast across Lake
Superior into Ontario this afternoon. Gusty south winds are
expected across Lake Michigan today, with a few gusts approaching
or reaching gale force, especially in the northeast portion of
the lake. Dense fog had formed over portions of nrn Lake MI but
has since dissipated. Will keep the Dense Fog Advisory in effect
for nrn Lake MI as the fog may redevelop late today and this
evening.

Winds will then gradually shift from southwest to northerly
tonight as a cold front tracks south, but southerly winds will
continue over far southern Lake Michigan as the front stalls.
Brisk northeast winds will then prevail over central Lake Michigan
on Sunday with lighter winds in the north, and variable winds in
the south where the stalled front remains. Modest east to
southeast winds will then develop over all of the lake Sunday
night as the stalled front moves north as a warm front. Brisk east
winds, possibly reaching gale force, are expected over the
northern tip of the lake late Sunday night into Monday morning.
Breezy south winds will develop over the remainder of the lake on
Monday.

Rounds of showers and thunderstorms are expected tonight into
Monday morning. A few of these storms could produce locally gusty
winds and hail.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory...WIZ051-WIZ052-WIZ059-WIZ060-WIZ065-WIZ066-
     WIZ071-WIZ072 until 4 PM Saturday.

LM...Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ868 until 1 AM Sunday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM
     Monday.

&&

$$

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