ST. LOUIS — A potent winter storm is going to affect Missouri and Illinois from Monday into Tuesday. But the biggest winter “punch” from this system will remain well northwest of St. Louis. It is a messy forecast, with a wide variety of conditions expected across the region from southeast to northwest. Variations will be possible over very short distances, even within the metropolitan St. Louis area, especially late this afternoon and tonight.
Phase 1: Rain and snow
There are basically three phases to this storm. Phase 1 arrives later this afternoon, roughly between 3 p.m. and 5 p.m. and lasts through about midnight. This will actually be the heaviest precipitation of the entire event. Rain and snow will spread from west to east across this afternoon, arriving in our western counties around 3 p.m. and then arriving in the St. Louis area sometime between 3 p.m. and 5 p.m.
The rain/snow line may split the metro in half, with the more likely areas for snow or a rain/snow mix this evening being northwest of I-44 in Missouri and north of I-70 in Illinois. The northwest metro may go all snow for a short time, with rapidly slushy accumulations possible. The rest of the metro will deal with a cold rain.
There is a chance some of our metro communities and interstates will be impacted by snow for the evening drive, especially I-70 from St. Charles to the west and Highway 61 from Lake St. Louis to the north. After a couple of hours, the rain/snow line will retreat rapidly to the north as temperatures start to warm up at cloud level. This will change virtually the entire viewing area to rain and drizzle by midnight, except for the far most northern communities up in Pike County, MO and Greene County, Illinois.
Phase 2: The slow part
Phase 2 of the storm runs from midnight tonight up to around midday Tuesday. This is the “slow” part of the storm; temperatures will be above freezing, and rain will be patchy and very light and drizzly. Not much will be going on during the morning rush hour on Tuesday.
Phase 3: The cold and wind
The final phase of the storm is tomorrow afternoon and evening. This is the colder, very windy, wraparound portion of the storm as it pulls away. We can expect very gusty winds and periods of wind-blown snowbursts and flurries. At times, it may look like it’s snowing pretty well, only to die off quickly. Temperatures will slowly fall back into the lower 30s by drive time. Some minor snow accumulation is possible with this phase, with a dusting to maybe one inch. Wind gusts up to 40 mph will be possible heading into the evening drive accompanying the snow bursts and flurries.
How much snow will we get?
Accumulations in this system are very tough to compute because we may see a couple of inches in the north metro this evening, but much of it will melt by morning. These forecast values represent the storm total, not necessarily what will be left on the ground in any one spot. Our far northernmost counties will have four to eight inches, but probably only realize about four inches when all is said and done.
In the St. Louis area, snow will range from virtually nothing on the southeast side of town, to a dusting, to maybe as much as two inches on the north side of town. Although it is unlikely anyone will have 2 inches to measure at any one time.
More snow later this week?
You may have heard of another system for Friday. Yes, it is possible. But the old saying we use often is one storm at a time and we need to get this storm out of the way to see how it changes the playing field for the rest of the week.
