ST. LOUIS — The first of two weekend weather systems will bring a light mix of rain and snow to the area this evening into early tonight. The light mix of rain and wet snow is forecast to begin in our southwest counties between 5 p.m. and 7 p.m. and reach the St. Louis area shortly thereafter. It should kick over to mainly snow by 9 p.m. with light snow expected over the metro and points east and south through about 2 a.m.–3 a.m.
I continue to think a stripe of light dusting, maybe up to a half inch, will be possible on grassy surfaces in the affected regions. But with temperatures just above freezing and the intensity remaining light, roads will remain wet. This has a similar look and outcome to the events we had last week.
Next week
A potent winter storm remains on track to impact the area from Monday night through late Tuesday night. Potent does not necessarily equal widespread heavy snow, although I still cannot rule that out.
This storm will have a lot of moisture, so we expect soaking rain with water equivalents of 1″ across the entire region. This storm will generate a significant amount of wind, so we expect widespread wind gusts of 35–45+ mph, especially Tuesday into Tuesday night.
What this storm does not have is a lot of cold air. There remains a big question as to the coverage and intensity of any snow in the colder parts of the storm. All this being said, I expect a mix of rain and snow be in the region by Monday evening.
By Tuesday morning, much of the area will have transitioned to a cold rain, with a cold rain likely through at least midday across most of the region. Colder air will start to be drawn into the backside of the storm by noon Tuesday with a slow transition back to heavy, wet, wind-blown snow over roughly the northwest half of the viewing area, and possibly the northwest half of the metropolitan St. Louis area.
How much snow?
The southeast half will remain rain Tuesday. Accumulations will come fast and furious along and northwest of I-44 in Missouri and west of I-55 in Illinois and across at least the far western parts of the region. The precipitation will transition to all snow across the entire region before ending late Tuesday evening.
It is still too early to think specific snowfall ranges at this point. However, it does appear likely that significant snow accumulations will occur northwest of St. Louis with at least some light accumulation possible for much of the rest of the viewing area. The greatest impacts from snow will be just northwest of metro St. Louis along I-70 from Wentzville to Columbia, north towards Troy and Bowling Green in Missouri and north of Jerseyville in Illinois.
A possible shift in the storm track
This storm is still over the northeast Pacific Ocean and has not had real-time sampling by our upper air network. That will change later today when the Hurricane Hunters fly a special mission into the system. This should improve the quality and confidence in our forecast. Even the smallest, 20-50 mile shift in the storm track could bring the heavier snow into metro St. Louis Tuesday evening, or it could keep us all rain. It’s just too early to say for sure.
