ST. LOUIS, MO - Another complicated forecast in a situation that will not produce a lot of snow. But still expect accumulating snow and sleet across much of the region late Saturday into Sunday.
This system has some parallels to the system that brought the quick hit of snow Thursday night into Friday morning but with a little more moisture available, and a bit stronger. It has some parallels to the first system of the year way back in January.
The air is very cold right not and very dry which will be a limiting factor to start with. It is also why the narrow band of radar returns showing up southwest of S. Louis at noon is not actually reaching the ground. It may bring a quick flurry or two but that's about it. However, in time, a southerly wind aloft will overcome this and snow should start to fall late tonight.
How much and when?
I expect a couple of waves of snow starting after 3am Sunday and continuing through about midday. There may very well be times where it is not snowing at all for an hour or more, then it picks up again. The heaviest snow will end up north of I-70 and generally north of a line from Troy MO over to near Vandalia IL. North of that line I expect 2-4” of snow by mid-afternoon Sunday.
Further south along and south of I-70, including all of metro St. Louis, I expect the multiple rounds of precipitation to start as snow but it will pretty quickly mix with then maybe completely change to sleet around sunrise Sunday. It may fall heavily for brief periods in this area but the mix of sleet with the snow should hold accumulations down in the 1-2” range by mid-afternoon Sunday.
Even further south, down towards Rolla and over to Perryville, it is entirely possible some freezing rain or drizzle may briefly mix with the snow/sleet mix towards the end of the event for a brief time.
All of this will translate into slick driving conditions across all of eastern Missouri into much of Illinois starting very late tonight, but especially during the morning Sunday into early afternoon hours.
Temperatures during this event will be warming slowly through the 20s and may get close to freezing by late Sunday afternoon from St. Louis to the south and southwest.