Breaking down the uncertainty in the forecast for winter weather this weekend
If you have been watching the forecast, you have probably noticed that there has been an increasing chance of observing wintry precipitation on Sunday. The problem is that although we know that wintry precipitation is likely, there is rather low confidence in the type of precipitation that will be observed for each area. Due to this issue, there is also uncertainty in the amount of precipitation, no matter the type, that will be measured for areas across Central Missouri. This is mostly because very warm air will be present leading up to this system.
Air temperatures today were well above average for this time of year, reaching the mid-60s and low 70s across Central Missouri. This trend will continue and potentially warm further on Friday and Saturday with continued sunshine, meaning that areas or surfaces where accumulation could occur on Sunday would have plenty of time to warm well above freezing.
One of these surfaces that would determine how much travel is impacted by this system is the roads. Thanks to the persistent sunshine, roadways could potentially get into the 70s and 80s by Saturday afternoon, and although there will be efficient cooling overnight, it may not be enough to reach the freezing mark before warming back up Sunday afternoon, leading up to the beginning of this system. This would mean that as long as road temperatures are above freezing, especially as snow starts, accumulation would not be as noticeable until the roads are cooled enough from continued precipitation. This could also lead to a very slushy and messy mix on the road if snowfall rates are high enough.
As for actual air temperatures on Sunday, they will start near freezing in areas like Columbia and Jefferson City, then warm into the upper 30s by the afternoon hours, which is above freezing. This system is expected to enter during the afternoon hours, where temperatures at least near I-70 will be above freezing. So as long as air temperatures stay above freezing, little impact will occur. The uncertainty arrives overnight as temperatures cool off and near freezing again. If temperatures can cool enough, the transition to wintry precipitation or snow will occur, and impacts will quickly arise.
Across Central Missouri, pretty much all types of precipitation will be possible. This is because warmer temperatures are expected to the south of I-70, whereas colder temperatures that are more favorable for wintry precipitation will be present along and to the north of I-70. If temperatures are below freezing at the very surface, but warmer than freezing in the upper levels of the atmosphere, precipitation will be falling as rain until it hits the ground, then freezing on impact. This is most likely a concern for areas along and south of I-70 for now, as areas to the north of I-70 will be dealing with a deep enough cold layer for mostly snow to occur.
Because all of these "ifs" are in place, and minor changes in data lead to significantly different outcomes, the overall probability of observing a specific type of precipitation in specific areas is rather low. It will be important to continue to look for updates as this system approaches to understand where the highest impacts may occur, but for now, areas north of I-70 can expect mostly snow, areas along I-70 can expect to be in the transition zone where a mix of wintry precipitation is possible, and areas south of I-70 can expect rain and freezing rain to be a bit more likely.
