NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 090240
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
840 PM CST Thu Jan 8 2026

.KEY MESSAGES...

- Heaviest rainfall looks to set up just north of the forecast
  area, although the band may still wobble southward and produce
  up to an additional half inch of rain across southwestern to
  central Wisconsin late tonight.

- The mild temps and rain into Friday will allow for ice to
  break up along rivers, with potential for ice jams. Isolated
  minor river flooding and ponding of water in poor drainage
  areas will also be possible as rain falls on partially frozen
  soil. A Flood Watch remains in effect for Sauk, Columbia,
  Marquette, and Green Lake Counties through late tonight.

- A line of thunderstorms developing in Iowa will likely affect
  southwestern to south-central Wisconsin late tonight. An
  isolated cell or two may produce gusty winds.

- Downward trend in snowfall for Saturday given a weaker system,
  but still a potential for some minor accumulations across our
  region. Uncertainty remains quite high at this time.

&&

.UPDATE...
Issued 841 PM CST Thu Jan 8 2026

Rainfall of 0.60-0.70 inches has fallen across Sauk to
Marquette Counties so far tonight, with lesser amounts
elsewhere. Latest runs of meso-allowing models are indicating a
shift northwestward with the heaviest precipitation, keeping it
out of the current Flood Watch area. That being said, a line of
thunderstorms has developed across southwestern Iowa, and are
expected to ride northeastward along the warm front draped from
approximately Dubuque to Sauk City to Beaver Dam. Storms would
be capable of producing rainfall rates to 0.5"/hr, but also are
expected to move eastward around 45 to 50 mph. Therefore, main
concern will be that storms may stall along the warm frontal
boundary and allow for multiple rounds of those higher rates in
the region of the Flood Watch. Therefore will allow the watch to
remain in play through its scheduled time (midnight CST).

This line of thunderstorms is also tapping into instability
within the warm sector (300 to 600 J/kg of MUCAPE), with weak
rotation along some of the cells directly along the warm
frontal boundary. This weak rotation indicates plenty of low-
level shear (0-3 km shear 40-45 kt, 0-1 km shear 40 to 50 kt),
and in combination with 0-3 km lapse rates around 5.5 degrees
C/km, there is at least potential for localized microburst
activity across southwestern to south-central Wisconsin. Still
not anticipating anything more than an isolated gusty (40 to 50
mph) thunderstorm at this time, but will be monitoring the line
closely as it moves in.

MH

&&

.SHORT TERM...
Issued 245 PM CST Thu Jan 8 2026

Tonight and Friday:

Forecast remains on track as low pressure centered over the
MO/IA border lifts northeastward through the evening bringing a
bout of moderate to heavy rain to southern WI. Will see rain
start to creep in from southwest WI through 21z and spread
northeastward through the evening. Overall there is ample
dynamics and synoptic forcing with this system given the
coupling of the upper-level jets left exit and right entrance
regions paired with mid-level dCVA, sub- 1000mb surface low and
accompanying 700mb frontogenesis band, and 850mb WAA all
aligning with unseasonable high PWATs around or exceeding 1".
The highest rain rates and heaviest rainfall looks to occur
between onset and 03z. The 12z CAMs have shifted the band of
heaviest rain a bit more northwest of HWY-151 where there is the
highest probability (>70%) of seeing over half an inch and even
pockets of 1 inch or more across the Wisconsin River Valley
(40- 50%).

Main impacts with the rain this afternoon and evening will be
the moderate to heavy rainfall falling over frozen grounds that
may result in localized ponding/minor flooding for low-lying
areas and roadways. Additionally the well above average temps in
the 40s and even 50s paired with the rainfall will also
contribute to ice on area rivers breaking up and potentially
jamming under bridges or around river bends resulting in minor
river flooding. Thus paired with 12z HREF LPMM exceeding 1 inch
will continue the Flood Watch for northwestern counties of the
CWA.

Meanwhile areas southeast of HWY-151 where the center of the
low is progged to track is looking to see lighter rainfall
amounts this afternoon and evening generally less than half an
inch. However, given the latest low track a smidge further north
as well, 12z models are pinging a bit more instability (250-500
J/kg) building into southeastern WI through the early evening
and cannot rule out seeing a few isolated thunderstorms. Main
area for this isolated activity will be in the warm sector of
the low where the favorable upper-level dynamics and nose of
50-60kt LLJ align with the higher moisture and instability into
the evening. Thus localized pockets of heavier rain associated
with any of this convective activity will be possible. Also
cannot completely rule out some small hail or even some of the
gustier winds mixing down to the surface this evening with the
elevated convection. So will need to keep an eye on how things
evolve over the next few hours.

The heaviest rain looks to wrap up later this evening over
southern WI as the low lifts northeast across the Straits of
Mackinac, but light rain looks to linger on the backside through
early Friday morning. Given a push of CAA also cannot rule out
see rain transition to a wintry mix through early Friday morning
before the drier airmass settles in. Otherwise, conditions will
be drying out through the morning/afternoon as weak high
pressure builds across the region with cooler, drier air, but
still looking at low 40s highs.

Wagner

&&

.LONG TERM...
Issued 245 PM CST Thu Jan 8 2026

Friday night through Thursday:

The models have changed in unison with a weaker scenario and less
expected snowfall for Sat-Sat nt. It is certainly possible the
models could return to greater cyclogenesis but for now going
with less QPF and snow.

A shortwave trough will be located over the srn Great Plains at 00Z
Sat while a stronger upper wave will be over srn Manitoba
extending swd through the Dakotas into NE. At the surface, weak
low pressure will track from the lower MS River Valley to the srn Ohio
River Valley by 12Z Sat, with an inverted trough extending to the
nw into WI and wrn Lake Superior where another weak low will be
situated near the approaching upper wave.

For Sat, the srn shortwave trough will track into srn WI ahead of
the amplifying wave from the nw. PVA and 850-700 mb frontogenesis
should result in widespread (70-80% ern WI and 40-60% south
central WI) light to moderate snowfall at least over ern WI.
Subsidence behind the initial shortwave trough and a dry slot
will slow the snowfall for the early afternoon, but wly winds and
cold advection will be increasing through the afternoon with
steepening low level lapse rates and the potential for snow
showers. Another vorticity maximum will arrive later in the
afternoon and evening, providing additional support for snow
showers. For Sat nt, a sfc trough and warm front, extending from
the consolidated low over srn Ontario and the lower Great Lakes,
will shift swd through srn WI, while the closed 500 mb low passes.
This will likely bring a return of a steadier light snow. QPF
values are ranging from 0.05 inches west of Madison to 0.20 inches
for far ern WI with 1-3 inches of snow possible. The light snow
will end Sun AM but brisk nwly winds and cold advection will
continue through the day.

At least a couple waves of low pressure tracking to the north,
and several shortwave troughs in nwly flow aloft are then expected
from Mon-Wed. The end result will be a deepening upper trough
over the central USA by Wed. Swly winds and warm advection will
initially occur with relatively mild temps returning for Mon-Tue
then a stronger cold front for Tue nt-Wed. 20-40 percent chances
for rain and snow trending to all snow are forecast during this
time. Polar air will be back in place for Wed-Thu.

Gehring

&&

.AVIATION...
Issued 841 PM CST Thu Jan 8 2026

Ceilings between 300 and 1100 ft are observed across southern
Wisconsin, with the highest ceilings within regions of rain
showers. Expecting IFR conditions to generally dominate through
the rest of the overnight hours. Patchy fog with visibilities
between 1/2 and 1 SM is expected across central Wisconsin,
including at SBM in between periods of rain showers.

A broken line of thunderstorms is developing across
southwestern Iowa, progressing northeastward quickly through the
remainder of tonight, generally staying north of ENW/UES/MKE. A
few gusts up to 40 kt are possible with these storms.

Southwesterly winds are expected to gust between 25 and 30 kt across
southeastern to far southwestern Wisconsin through late
tonight, shifting to become southerly as low pressure
approaches to the south, then rapidly shifting to become
northwesterly late tonight into early Friday morning as low
pressure exits and a strong cold front pushes through southern
Wisconsin. Expect gusts around 25 kt to continue after the
frontal passage, with a brief period of rain and snow mix
possible along this front. Ceilings will recover as the front
moves through, with MVFR to VFR dominating by midday Friday.

MH

&&

.MARINE...
Issued 245 PM CST Thu Jan 8 2026

Southerly winds across Lake Michigan will gradually turn as low
pressure lifts from the MO/IA border into the northern half of
Lake Michigan overnight. Will see gusty south to southeasterly
winds over the southern half of Lake Michigan this evening as
the low approaches then veering to southwest overnight. Lighter
more easterly winds are expected for the north half of the lake,
but gradually weaken as the low pushes northeastward into
Friday morning. Behind the low, expect more north to
northwesterly winds pick up into Friday morning. Given the tight
pressure gradient on the backside of this departing system,
will see gusts of 30 knots and a few brief gale force gusts
through late Friday morning, especially along the eastern
lakeshore. Winds will gradually weaken Friday afternoon as high
pressure works its way across the Lake Michigan through Friday
night. Then looking at two areas of low pressure one coming up
from the southern Plains and another digging down across the
Upper Midwest merging over the Great Lakes for Saturday. Expect
west-northwesterly winds over Lake Michigan to increase on the
backside of this deepening low pressure as it lift into eastern
Ontario/Quebec. Will be a potential for gales across the open
water, but still some uncertainty on the overall strength of
the low pressure. Then another high pressure will build across
the region for Sunday before another system traverses the
region early next week.

Wagner

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch...WIZ046-WIZ047-WIZ056-WIZ057 until midnight
     Friday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 8 AM
     Friday.

&&

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, X, and YouTube at:
www.facebook.com/NWSMilwaukee
www.x.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee