Areas of light freezing drizzle and freezing fog will linger through 3 AM this morning across areas northwest of Madison. Otherwise, rain will move into the area with low pressure after 3 AM, then will change to all snow later this morning. The low pressure system responsible for the wintery weather will track northeast into southern Wisconsin by sunrise today, and then continue northeast into Upper Michigan by late this afternoon.
As the warmer air continues to push into southern Wisconsin early this morning, surface temperatures will be slow to respond, due to the fresh snow cover blanketing the region, and the persistent cold of the last few days. Hence this thermal profile of the atmosphere will result in patchy light freezing drizzle, with freezing fog, over portions of south central Wisconsin northwest of Madison through 3 AM, before temperatures warm to above freezing, changing any freezing drizzle to drizzle and rain for the remainder of the early morning hours.
A winter weather advisory for a mixture of freezing drizzle and freezing fog is in effect for Sauk, Columbia, Marquette and Green Lake counties until 3 AM this morning. Any freezing drizzle and freezing fog will combine to create slippery conditions on untreated roads and walks.
The precipitation will begin to mix with or change over to snow west of Madison by sunrise today, becoming all light snow west to east across southern Wisconsin by late this morning. The Monday morning commute will be affected by this system. Westerly winds behind the low pressure system will become gusty by late morning, with blustery conditions persisting through the afternoon.
Latest icing reports to the NWS - Sullivan office.
NWS Milwaukee/Sullivan - Kavinsky/DDV/Wood