NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 042117
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
317 PM CST Sun Jan 4 2026

.KEY MESSAGES...

- Light wintry mix of freezing rain, sleet, and snow near & especially
  north of I-94 and US-18 this evening (~4-10 PM). A light
  glaze of ice can't be ruled out on elevated & untreated
  surfaces.

- Patchy freezing fog & possible early Monday morning.

- Additional chances (~30-50%) for mostly rain Tuesday. Some
  precip could start as rain-snow mix or freezing drizzle.

- Temperatures trending well above normal Wednesday through Thursday.

- Becoming colder & more active Friday through Sunday, with
  multiple chances (~20-40%) for rain and snow.

&&

.SHORT TERM...
Issued 320 PM CST Sun Jan 4 2026

Tonight and Monday:

Synopsis/Mesoanalysis: Water vapor imagery shows a shortwave trough
near the South Dakota-Minnesota border early this afternoon.
Precipitation is ongoing in advance of the wave, with low level warm
advection helping to drive a mix of wintry precip types at upstream
stations. Expect the southern edge of this area of precip to clip
southern Wisconsin this evening, with a mix of light freezing
drizzle, sleet, and snow being favored given continued warm
advection in the lower part of the column. Best precipitation
potential is to the north of I-94 and US-18, where the strongest
warm advection-driven ascent will reside. A light glaze of ice is
possible in locations experiencing wintry precipitation. The
responsible wing of warm advection will push east of the area after
midnight, allowing most wintry precip to conclude. Low pressure will
move into the Upper Mississippi Valley late tonight, with attendant
south-southwest winds maintaining moisture in the lower part of the
column. The moist conditions, along with weakening surface winds,
could lead to patchy fog development from the predawn hours into
early Monday morning. With temperatures below freezing, freezing fog
and slick spots are possible. Budget a few extra minutes of time if
traveling north this evening or commuting Monday morning. Fog and
slick spot potential should improve by late morning Monday.

This Evening: Expect wintry precip to move into the northern half of
the area between ~4-10 PM. Anticipate that the majority of
precipitation will occur to the north of I-94 and US-18, where
increasing warm advection & affiliated isentropic ascent will be
greatest. Have thus depicted the highest precip probabilities (~40-
80%) over this part of the area through mid-evening. While weaker in
magnitude, model guidance does maintain some weaker lift south/into
the I-94 and US-18 Corridors, so did maintain some slight chance to
chance (~15-35%) precip probabilities further south into the Madison
& Milwaukee metros. Given low level warm advection & an attendant
warm nose aloft, do expect that sleet and/or light freezing rain
will comprise a good portion of the wintry precip falling this
evening. With surface temperatures below freezing, a light glaze of
ice is possible on untreated surfaces in areas experiencing
precipitation. Best potential will be in central and east-central
Wisconsin, where probabilistic guidance shows ~10-30% chances for a
glaze (~0.01").

Late Tonight into Monday Morning: Wintry precipitation is expected
to taper after midnight as the deeper lift shifts east. Despite
waning precip chances, boundary layer conditions will remain moist
through the remainder of the overnight period thanks to south-
southwest surface flow. With winds forecast to taper during the
predawn hours, could thus see some fog development across the region
during the late overnight/early morning hours. Peak potential for
fog would be between 3-9 AM. With temperatures below freezing,
freezing fog and slick spots would be possible in any locations
experiencing fog.

Quigley

&&

.LONG TERM...
Issued 320 PM CST Sun Jan 4 2026

Monday night through Sunday:

Synopsis: A second upper disturbance will cross southern Wisconsin
Monday night into Tuesday, bringing chances for mostly rain
areawide. Some precipitation could start as freezing drizzle or a
light rain-snow mix, with precipitation transitioning to all rain
after sunrise on Tuesday. Mostly dry conditions are expected
Wednesday through Thursday as high temperatures trend well above
normal. Chillier air will gradually work into the region Thursday
night into next weekend, along with multiple chances for rain and
snow.

Late Monday Night through Tuesday: A second system will bring
additional precip chances to the area. Expect an initial round of
precipitation to focus along a frontogenesis band in the 700-500 mb
layer over northern Wisconsin Monday evening/night, with additional
precip filling into central and southern Wisconsin during the
predawn hours Tuesday as the upper low approaches/moves overhead.
Given potential late overnight onset of precip, temperatures may be
cold enough for some rain-snow mix or light freezing drizzle at the
very start of precipitation, with a transition to all rain occurring
as temperatures climb above freezing following sunrise. Will thus be
monitoring trends with this second system, as some minor impacts to
the Tuesday morning commute would be possible in any spots seeing
wintry precipitation.

Quigley

&&

.AVIATION...
Issued 320 PM CST Sun Jan 4 2026

Mid-upper clouds continue to fill in across southern Wisconsin this
afternoon, with a continuing downward trend in CIGs & potential MVFR
anticipated through the remainder of today. An upper disturbance
will cross the western Great Lakes this evening, bringing chances
for SN, UP, and FZDZ to locations near and especially north of I-94.
Have continued PROB30 mentions at the I-94 aerodromes in the 18Z
update, with prevailing precip mentions being inserted at SBM where
confidence is greatest. Removed PROB30 mentions at JVL and ENW,
where precip potential has become more uncertain. Will continue to
monitor trends and make amendments in if necessary. LLWS is also
possible as winds increase ahead of the approaching disturbance this
evening. Winds will turn out of the west-northwest Monday morning as
low pressure shifts east of the region.

Quigley

&&

.MARINE...
Issued 320 PM CST Sun Jan 4 2026

1022 mb high pressure is moving east of Lake Michigan this
afternoon, resulting in light southeasterly winds. Currently over
the northern Great Plains, 1002 mb low pressure will move into the
northern Mississippi River Valley this evening, resulting in
increasing southerly winds across the waters. Gusts between 25-30
knots will be possible through daybreak Monday. Winds will veer
southwesterly and eventually westerly Monday morning as the
aforementioned area of low pressure crosses the waters, gradually
weakening in the process. Rain-snow mix and freezing drizzle are
forecast ahead of the approaching low tonight. Winds will become
light and variable Monday afternoon as 1012 mb high pressure moves
across Lake Michigan.

Southerly winds will become established Monday night ahead of a new
area of 1004 mb low pressure forming in the northern Great Plains.
The low will approach and ultimately cross Lake Michigan Tuesday
morning, resulting in a west-northwest wind shift by the afternoon
hours. Gales are not anticipated during the low's passage.
Additional rain and rain-snow mix are forecast Tuesday in
affiliation with the low. West to southwest winds will prevail
through Wednesday afternoon, turning southerly Wednesday night into
Thursday. A cold front will cross the waters Thursday night,
bringing north-northeast winds by Friday morning. Rain and snow will
accompany the passing cold front Thursday night through Friday.

Waves and southerly winds will increase in nearshore zones this
evening as low pressure approaches from the Northern Plains. A Small
Craft Advisory remains in effect between 8 PM CST and 6 AM CST
Monday in all nearshore zones. Freezing drizzle and rain-snow mix
will accompany the approaching low. Winds will quickly subside
during the day Monday. Additional Small Craft Advisory conditions
are possible Friday night into next weekend.

Quigley

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...8 PM
     Sunday to 6 AM Monday.

&&

$$

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