NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 172339
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
639 PM CDT Tue Mar 17 2026
.KEY MESSAGES...
- Light accumulating snowfall will occur tonight into Wednesday
morning. Around 1 inch of snow is forecast, possibly up to 2
inches southwest of Madison. A few hours of freezing drizzle
is possible as the snow exits.
- 50 percent chance for light rain Wednesday night but could
linger into Thursday morning. A very brief period of freezing
rain will be possible over east central WI late Wednesday
night.
- A warming trend is expected from Wednesday into Saturday.
&&
.UPDATE...
Issued 639 PM CDT Tue Mar 17 2026
WAA is slow to start up behind the exiting high pressure system
and incoming shortwave this evening. Sfc dewpoint depressions
are fairly large this evening around 15 to 20 degrees. Which
will impact the start time of snow this evening. Thus the low
reflectivities across western Wisconsin are likely not making
it to the ground yet and may not for another couple hours or
until we start to see some of the 30 to 40 dbz returns.
Confidence remains high on getting some light snow overnight and
the mid level WAA remaining through the overnight. As this warm
nose of air moves in aloft early Wednesday morning, there is a
concern for a couple hour window for snow to become freezing
drizzle as we loose cloud ice.
Patterson
&&
.SHORT TERM...
Issued 206 PM CDT Tue Mar 17 2026
Tonight through Thursday:
The sfc ridge over srn WI will shift ewd this evening with the
onset of sly winds and warm advection expected. In nwly flow
aloft, a vorticity maximum over MN will track across the area,
while a tight 700 mb baroclinic zone moves ewd across srn WI.
850 mb warm advection will also ensue but mostly push through
the area on Wed. Dry air in place will initially limit snow
onset, but it will spread west to east from 02Z-06Z. 4-5 hours
of light snow is expected followed by a few hours of freezing
drizzle as dry air invades the mid levels. Initially a very deep
dendrite zone is expected but the entire layer will quickly
warm toward -10C with snow changing to areas of freezing
drizzle. Overall the fcst soundings suggest only weak lift,
strongest over sw WI. Around 1 inch of snow is forecast,
possibly two southwest of Madison.
Air temps will then warm above freezing for Wed afternoon on
swly winds, but sunshine is very uncertain with lingering
stratus probable. Another shortwave trough will approach from
the nw late Wed nt and pass early Thu. The models are differing
with the amplification of this wave and how widespread the rain
showers will be. Went 50-60 percent for rain late Wed nt,
possibly lingering into Thu AM.
Gehring
&&
.LONG TERM...
Issued 206 PM CDT Tue Mar 17 2026
Thursday night through Tuesday:
The extended models agree on a shortwave trough tracking across
the nrn Great Lakes Thu nt-Fri, accompanied by a wave of low
pressure and weak cold front. Any precipitation is expected to
remain to the north.
A well develop low pressure area will then track ewd across
Ontario into Quebec for Fri nt-Sat. Swly winds and warm
advection will boost high temps into the 60s on Sat west of the
MKE metro. A cold front of some degree is then expected to pass
Sat nt-Sun, followed by an area of high pressure across the
Great Lakes into Mon. Thus temps will cool back down to normal
for the early portion of the week.
Gehring
&&
.AVIATION...
Issued 639 PM CDT Tue Mar 17 2026
VFR to IFR conditions are expected through the period. Snow will
be slow to start here across southern Wisconsin as dry air
erodes away at the precipitation. Virga will be more likely to
start out ahead of any sfc snow. As light snow starts to make it
to the ground tonight, visibilities could fall to around 1-2
SM. Snow is expected to be a light powdery snow. Ceilings are
expected to fall around 2-4 kft overnight as the snow moves
through. Early Wednesday morning (roughly 2 to 8 AM) as the snow
is starting to move east out of the state, there is a chance
that snow turns to freezing drizzle. This window for freezing
drizzle will be small around an hr maybe two for any given
location. Should freezing drizzle occur only a glaze of ice is
expected. Snow totals As snow and freezing drizzle move out
shortly after sunrise, the MVFR ceilings will persist through
the rest of the Wednesday morning. The cloud deck will rise to
VFR and become scattered Wednesday afternoon. A few areas may
see clear skies for an hour or two before more high level clouds
return.
Southwest winds this evening will become due southerly tonight
and may be breezy at times. Light southwest to south winds
are expected Wednesday afternoon through Wednesday night.
Patterson
&&
.MARINE...
Issued 206 PM CDT Tue Mar 17 2026
Light to modest northwest winds will shift to southwest by late
today, as high pressure around 30.2 inches moves across Lake
Michigan this evening. Modest to breezy southwest winds will
prevail tonight into Wednesday night as low pressure of 29.7
inches progresses through the southern Canadian Prairies into
Ontario. A weak cold front will then slowly pass Thursday into
Thursday evening with light and variable winds.
Small Craft Advisory conditions are possible Wednesday morning
north of Port Washington for persistent south to southwest winds
and building waves.
Gehring
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&
$$
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