UPDATE: Messy Thursday forecast leads to two most-likely scenarios
UPDATE 12/6/18: The system left a dusting on grassy and elevated surfaces for most of mid-Missouri with up to 2" for some north of I-70 where snow fell heaviest. Roads are wet and roads that don't dry and aren't treated may form patchy black ice overnight with temps cooling into the 10s. Please continue to use caution while driving overnight and in the morning, especially on lesser-traveled roads and parking lots, as well as walking on sidewalks.
It's all gone. A nice dusting to 2" (north of I-70) on grassy & elevated surfaces w/ a wet snow. Clouds are hanging out for a bit as the sun goes down. Then as temps cool this evening and overnight roadways that haven't dried may form patches of black ice. pic.twitter.com/Vl4TwuUL5q— Kenton Gewecke (@KentonGewecke) December 6, 2018
COLUMBIA - Thursday, December 6 looks like a doozy in terms of the weather forecast. That's because as a cold front moves through, bringing moisture with it, temperatures will be cooling. As we know, only a couple degrees difference can lead to a different outcome. Because of this, I've created a two-scenario forecast so everyone can anticipate both options. There is a warm scenario, leading to very few problems on the roads and only minor snow accumulation on the grass and vehicles, and a cold scenario which would lead to additional snow accumulation and a deterioration of road conditions, especially bridges.
Air temperatures are expected to start above freezing at the onset of this system. Rain will fall, possibly even creating drizzle and fog decreasing visibility. Then as the cold front moves through, temps are expected to fall to around freezing by mid to late morning, changing the rain to snow. How far they fall will determine the warm scenario or cold scenario.
Ground temperatures are important when considering travel. Our top soil is currently at temperatures in the middle 30s. This should hold off some slick spots as this system starts to allow for snowfall. However, should the cold scenario take place, slick spots are likely to form, especially on bridges because they don't have any warm soil under them. Also note that road crews won't treat roads until any rainfall stops, otherwise it'd wash away.
Clouds play another roll here, including the air temperature around the clouds. At this point it looks like temperatures will be freezing at the cloud-level, but closer to above freezing near the surface, at least at the onset. How thick the clouds become will also play a roll in the physics of this system. We'll need to keep an eye on the temperatures near the clouds, especially after the sun comes up...
Sunshine will play a roll here due to the timing of this system. Likely, at the onset, it will still be dark. However, as the sun comes up it will warm and potentially insulate the clouds. The sun may also warm us in the midday/afternoon time period if the clouds aren't thick enough to hold it off, which would warm us enough to also only see the warm scenario. All of this will factor into the physics of this system and could change the precip. type.
Winds will change direction as the cold front moves through. Winds will change from the southwest to the northwest and north. This will help usher in cooler air at the surface, likely decreasing the warmer layer near the surface I previously mentioned.
All of these factors must be taken into the forecast. You can see why this is such a tricky one.
The onset will likely begin in northern mid-Missouri between 4am and 6am and slowly push south through the morning and midday, exiting southern mid-Missouri by 3pm to 6pm. Overall, this is a 12-hour system for our region.
The onset will likely begin in northern mid-Missouri between 4am and 6am and slowly push south through the morning and midday, exiting southern mid-Missouri by 3pm to 6pm. Overall, this is a 12-hour system for our region. pic.twitter.com/OokFm25SP5— Kenton Gewecke (@KentonGewecke) December 6, 2018
Remember, with temperatures this close to freezing, and all the factors mentioned above, this forecast is not only difficult, but it can change in no time. Therefore, here are the two most-likely possibilities so you are prepared no matter what.
WARM: This is assuming our temperatures stay at or just above freezing at the surface. In this case, rain, drizzle and wet snow will not create many problems, but a few slick spots will still be possible on roads. You should always drive with caution in any type of winter weather. A dusting to 0.5" is possible on grassy and elevated surfaces such as vehicles.
COLD: This is assuming temperatures cool to at or just below freezing. This would lead to more snowfall with accumulations from 0.5" to 2" possible. More roads will have slick spots, especially bridges because they don't have any soil below them to help counter the cold air temps.
Due to many factors, there are two most-likely scenarios for Thursday. The warm scenario will see less snowfall and fewer slick spots on roads. The cold scenario will create more snow accum. and slicker roads. Stay tuned, it only takes a few degrees... pic.twitter.com/WZn2olR6aw— Kenton Gewecke (@KentonGewecke) December 6, 2018
Don't forget that with wet roads leftover after this system, temperatures will be going below freezing in the evening and overnight, which could lead to black ice on untreated roads if they don't dry up first. Use caution when driving.
Be sure to check in with meteorologist Tim Schmidt on KOMU 8 News Today starting at 4:30am for the latest data and track. Weathercaster Matt Beckwith will have more details on KOMU 8 News at Noon. Chief Meteorologist Kenton Gewecke will have the wrap-up and discussion of this system on KOMU 8 News First at 5, 6, 9 & 10.
Stay up to date with the latest forecast, video updates, live streaming newscasts, and interactive radar plus live traffic grids on the KOMU 8 Weather & Traffic App.