ST. LOUIS — There are a lot of details in this forecast but there is one event you should be aware of. A flash freeze event Friday afternoon and evening is looking more and more likely. Rapidly falling temperatures will combine with strong and potentially damaging wind gusts of 50+ mph, along with bursts of snow and flurries, to make the Friday evening commute a real struggle. Extreme cold is expected to follow the snow, with wind chills dropping to just above zero by 10 p.m. on Friday.
A powerful winter storm is going to track through the St. Louis area Thursday night and Friday. This does not mean there will be widespread, heavy snow. There is more to this storm than just snow.
The system will enter the region Thursday night with widespread rain. Winds may even gust to between 40 and 50 mph at times, especially over southern Illinois and southeast Missouri. There is a chance the rain may very briefly start as some wet snow north of I-70, but that will quickly give way to rain as temperatures warm. The Friday morning commute will be very wet and still pretty windy.
Around midday, arctic air will get pulled into the system from the west and rapidly get sucked in towards the center of the storm. This will start a steady transition from rain to snow from west to east between midday and 4 p.m. The amount of potential snow accumulation will be directly tied to how fast the cold air gets pulled into the storm. If it arrives faster, more snow will fall. If it arrives more slowly, the chances for meaningful accumulation diminish.
I expect a changeover to snow in metro St. Louis by mid-afternoon Friday, with snow tapering to wind-blown snow showers or flurries after sunset. Given the extremely dynamic nature of this system, I’m still not ready to put firm numbers on it. A couple of inches of snow is not out of the question for metropolitan St. Louis and points north, west and southwest.
The potential impact to travelers for the Friday evening commute is likely to be significant even with just a light dusting of snow. Dangerous cold follows this storm, with temperatures in the single digits and teens for highs over the weekend and overnight lows near or below zero.
There is another system coming for Sunday that will produce all snow. At this point, the most significant accumulations are targeting southern Missouri, but a few inches are possible as far north as I-70 and St. Louis. This storm could produce some beefy snowfall south of St. Louis on Sunday in places like Rolla, Salem, Farmington and Perryville.
