From LSX:
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAINT LOUIS MO
823 PM CST THU DEC 31 2020
UPDATE
ISSUED AT 804 PM CST THU DEC 31 2020
A BAND OF WINTRY PRECIPITATION HAS MOVED NORTH INTO SOUTHEAST
MISSOURI AND THE FAR SOUTHERN REACHES OF THE CWA AHEAD OF THE
PREVIOUS FORECAST. THIS BAND IS EXPECTED TO MAKE IT TO THE ST.
LOUIS METRO/COLUMBIA METRO REGION AROUND 04Z. WHILE THE LEADING
EDGE OF THIS PRECIPITATION COULD START AS SNOW OR A WINTRY MIX, IT
IS ANTICIPATED TO QUICKLY TRANSITION TO FREEZING RAIN. FREEZING
RAIN HAS BEEN REPORTED IN FARMINGTON, MO WITH THIS FIRST BAND.
A BRIEF BREAK IN PRECIPITATION IS POSSIBLE AFTER THIS FIRST SHOT
OF WINTRY MIX/FREEZING RAIN, HOWEVER THE GAP IN REFLECTIVITY HAS
BEEN FILLING IN OVER THE PAST HOUR. I CANNOT RULE OUT LIGHT
PRECIPITATION FALLING IN THE GAP BETWEEN THE FIRST ROUND OF
PRECIPITATION AND THE SECOND, MORE ROBUST ROUND OVERNIGHT.
MRM
In other words, it's moving an hour ahead of schedule.