textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A Cold Weather Advisory is in effect late tonight through Monday morning across all of southern Wisconsin. Bitter cold wind chills of 23 to 29 below zero are expected during this period. Wind chills in the teens below zero are expected Monday afternoon into Tuesday morning.

- Light accumulating snow is expected this afternoon and evening, with new accumulations around 1 to 2 inches across the area. Gusty northwest winds later tonight into Monday may lead to some areas of blowing and drifting snow. Watch for slick spots and pockets of reduced visibility. - A Gale Warning is in effect for all of Lake Michigan later tonight through Monday afternoon. A Heavy Freezing Spray Warning is in effect as well later tonight through Tuesday morning.

SHORT TERM

Issued 421 AM CST Sun Jan 18 2026

Today through Monday night:

There is still some pesky flurry activity lingering in eastern parts of the area early this morning, as one last area of weak differential CVA pushes through with moist low levels in the dendrite snow growth zone. This activity should push off to the east by sunrise. There may be some pockets of clearing at times into this morning, before more clouds move in by midday as warm air advection develops.

Models are still in good agreement with a period of light snow moving east southeast through southern Wisconsin this afternoon into this evening, exiting to the east/northeast later tonight. This is being driven by a passing Arctic cold front this evening, with some low level frontogenesis response ahead of and behind it and some differential CVA from a shortwave trough passing just south of the area. Forecast soundings are saturated in a deep layer with the dendrite snow growth zone tapped in the low levels.

Look for the snow to move east into the area by middle afternoon, peaking late afternoon and early evening, then gradually exiting from west to east late evening into the overnight hours. Snowfall rates should be up to one quarter inch per hour, so a steady, light snow is expected. Snow to liquid ratios will be around 20 to 1 or so, with one to two inches of fluffy accumulation expected.

Strong cold air advection on gusty northwest winds are expected after the Arctic cold front moves through. This may cause some blowing and drifting snow, given the fluffy nature of the new snow, as well as recent snowfall that probably has not compacted much. Some visibility reductions may occur, as well as some drifting on north to south roads. Will need to monitor if this will be a more widespread issue in later forecasts.

The cold air advection will bring much colder temperatures and wind chills into the area later tonight into Monday night. Lows should drop into the single digits below zero over most of the area, with wind chills in the 23 to 29 below zero range late tonight into Monday morning. A Cold Weather Advisory is in effect for the entire area during this period. Fairly confident wind chills will not drop to the 30 below zero or colder thresholds at this time.

Wind chills should remain in the teens below zero Monday afternoon into Tuesday morning, with gusty west northwest winds and temperatures in the single digits above zero Monday afternoon, with lows Monday night in the single digits below zero.

Wood

LONG TERM

Issued 421 AM CST Sun Jan 18 2026

Tuesday through Saturday:

Synopsis: Mean upper troughing will continue to linger from the Hudson Bay into the western Great Lakes through the duration of the long term period. Given the persistent synoptic pattern, southern Wisconsin will remain favorably positioned for impacts from clipper systems, with attendant surface cold frontal passages bringing additional bouts of very cold temperatures and wind chills.

Tuesday evening into Wednesday is currently favored for the most widespread snow potential across the area, with some signal for accumulation in probabilistic forecast guidance. Low level winds will turn northwesterly behind the Tuesday evening and Wednesday system, with chilly temperatures and wind chills settling in for the Wednesday night through Thursday time frame.

Signals for another clipper system are evident during the Friday to Saturday time period, though high uncertainty remains regarding wintry precipitation potential in southern Wisconsin. Of greater confidence, however, is that another pull of Arctic air will sag into the western Great Lakes with the affiliated clipper system during the Friday-Saturday time period. Additional very chilly temperatures and wind chills are thus anticipated from the end of the upcoming work week into next weekend.

Tuesday Night through Wednesday: Expect the next best chances for widespread snowfall during this time frame. Snow will initially focus along bands of 1000-700 mb frontogenesis & warm advection Tuesday night through early Wednesday, with activity trending more scattered in nature into Wednesday afternoon as a cold front moves east of the area and cold advection becomes predominant. Probabilistic forecasts from global ensemble guidance and the NBM indicate some potential for accumulation, though confidence in probabilities at any given location are low, due to lingering north-south dispersion regarding system track between ensemble members. Will continue to monitor trends and offer additional details as track trends clarify in coming forecasts.

Wednesday Night through Thursday: Expect another round of chilly temps and wind chills as Arctic air re-establishes over the western Great Lakes. Have maintained temperature and wind chill forecasts from the NBM, which would keep conditions a touch milder than Cold Weather Advisory criteria. Any colder shifts, however, would push wind chills toward headline thresholds during the Wednesday night through Thursday morning period. Will thus be closely monitoring trends over coming forecasts.

Thursday Night through Saturday: Guidance suggests that another disturbance will cross the region, with possible phasing between multiple areas of upper forcing making precipitation chances more uncertain relative to Tuesday night into Wednesday. Regardless of whether/not precip occurs, there is a much stronger signal for another surge of Arctic air to make it into the area along/behind the passing system. If current forecasts from the NBM verify, this next Arctic surge could be even colder than the one expected during the Wednesday night-Thursday period. Will thus be monitoring for possible cold weather headlines as this part of the period pulls closer.

Quigley

AVIATION

Issued 421 AM CST Sun Jan 18 2026

There is still some pesky flurry activity lingering in eastern parts of the area early this morning. This activity should push off to the east by sunrise. There may be some pockets of clearing at times into this morning, as well as ceilings varying between 1500 and 4000 feet AGL, before more widespread ceilings around or below 2500 feet AGL move in by early this afternoon. Southwest winds are expected to remain gusty into midday, before weakening somewhat this afternoon.

Models are still in good agreement with a period of light snow moving east southeast through southern Wisconsin this afternoon into this evening, exiting to the east/northeast later tonight. This is being driven by a passing Arctic cold front this evening.

Look for the snow to move east into the area by middle afternoon, peaking late afternoon and early evening, then gradually exiting from west to east late evening into the overnight hours. Snowfall rates should be up to one quarter inch per hour, so a steady, light snow is expected. One to two inches of fluffy accumulation is expected. Ceilings should be in the 1500 to 2500 foot AGL range, with visibility of 1 to 2 miles in the light snow.

Gusty northwest winds are expected by later tonight, after the Arctic cold front moves through. This may cause some blowing and drifting snow, given the fluffy nature of the new snow, as well as recent snowfall that probably has not compacted much. Some visibility reductions may occur, as well as some drifting on north to south runways.

Wood

MARINE

Issued 421 AM CST Sun Jan 18 2026

Low pressure around 29.8 inches will move from northwest Minnesota this morning to the eastern Upper Peninsula of Michigan today. West to southwest winds are expected today across Lake Michigan.

The low will then strengthen to around 29.5 inches as is shifts into eastern Ontario tonight, and into Quebec on Monday. An Arctic cold front will move across the lake later this evening, with northwest gales and heavy freezing spray expected behind the front later tonight through Monday afternoon.

A Gale Warning is in effect for all of Lake Michigan later tonight through Monday afternoon. A Gale Warning is in effect for the nearshore waters of Lake Michigan later tonight through Monday morning. A Small Craft Advisory will be needed Monday afternoon and evening for lingering gusty northwest winds.

The strong winds will combine with building waves and cold temperatures to bring heavy freezing spray later tonight through Tuesday morning. A Heavy Freezing Spray Warning is in effect during this period across all of Lake Michigan. Some freezing spray is possible in the nearshore waters, mainly toward the open waters.

High pressure around 30.5 inches will shift from the northern Plains into the Lower Mississippi River Valley Tuesday, with winds across Lake Michigan shifting west to southwest.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...Cold Weather Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065- WIZ066-WIZ067-WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...3 AM Monday to noon Monday.

LM...Gale Warning...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563- LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...midnight Monday to 6 PM Monday.

Heavy Freezing Spray Warning...LMZ080-LMZ261-LMZ362-LMZ364- LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675- LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876- LMZ878...midnight Monday to noon Tuesday.

Gale Warning...LMZ643-LMZ644-LMZ645-LMZ646...midnight Monday to noon Monday.