Weather Alert Day: Winter storm warning issued in Mid-Missouri, winter storm watch expanded ahead of weekend storm

UPDATES:

The National Weather Service has extended the Winter Storm Watch area in mid-Missouri and issued a cold weather advisory area-wide.

The ABC 17 Stormtrack Weather Team has issued a Weather Alert Day from Friday morning through Monday morning as dangerous cold returns to the region. A low-pressure system to our southwest will pull moisture in and bring the potential for accumulating snow to Mid-Missouri.

SETUP:

The upper-level pattern combines the northern jet stream we've been dealing with all week, with an additional jet stream from the South Pacific that develops in conjunction with an upper-level wave that moves in from the southwest this weekend.

The confluence of cold and dry air from the north with moist and active flow nudging in from the south is creating potential for a winter storm nearby, potentially impacting mid-Missouri with cold AND measurable snow.

UNCERTAINTY/LIMITING FACTORS:

We are currently watching guidance converge on the likelihood of impactful snow totals in Mid-Missouri. As mentioned above, the low that develops to our west, orienting the southern jet stream that sends waves of disturbances our way, is just coming ashore on the west coast. This system has been sampled by reconnaissance planes in an attempt to improve forecasts across the country. The northern jet stream that sends small disturbances and weak cold fronts this week is set to make a bigger push of cold air just ahead of the southern stream's moisture. This will bring dangerous cold air ahead of snow, leaving us totally dry on Friday, but frigid.

Cold and dry air at the lowest levels of the atmosphere could eat away at snow as it falls, but as moisture levels increase in the forecast, this is becoming less of a factor for most. It could still create a sharp drop in snow totals in the extreme northern tier of mid-Missouri to the Iowa border. On the flip side of the coin, colder air will create higher snow-to-liquid ratios that will make snow accumulation more efficient.

As of Wednesday evening, global forecast models have come into better agreement that the low pressure will take more of a northerly track, bringing more moisture north into Missouri, thus bringing the potential for accumulating snow. This continues now into Thursday morning, further solidifying confidence in high snow totals and raising questions about increasing them.

TIMING:

It's going to be cold, likely colder than it has been all season. Timing regarding the cold sets in Friday, behind a cold front that works in early in the morning. High temperatures look likely to remain near 10° both Friday and Saturday. Cold persists until we warm into the beginning of next week. Lows are expected in the single digits or colder through at least Monday.

Snow showers are expected to begin across southwest Missouri late Friday night, spilling into Mid-Missouri before dawn Saturday and continuing through late morning or midday Sunday. The highest amounts are expected to be south of Highway 50.

HAZARDS/IMPACTS:

Snowfall amounts will be highest for areas near the Lake of the Ozarks and points south, closer to the center of low pressure in Arkansas.

New data is starting to point towards the need for higher totals. Probabilities of at least 4 inches are now near 90% in Columbia, which makes 6" more attainable. With time, we may need to increase totals on the map above, so consider implications of the high sides of these ranges and prepare for that. Stay tuned to the forecast as details evolve. The zone we're most uncertain about is along Highway 24 and northward, where drier air could eat away at totals more quickly.

Our greatest confidence is in extreme cold; with frozen pipes, car trouble, and frostbite possible with prolonged exposure this weekend. The window of deepest cold is from Friday morning through Saturday Sunday morning. Wind chills are tough to forecast at this distance, but are likely subzero at times, especially Saturday morning.

Roads will be quite slick with very low visibility between Saturday morning and Sunday morning with snow moving through. Treatment could be tough on Saturday as air temperatures could dip below zero in the morning.

Make sure you have the ABC 17 Stormtrack Weather App to keep an eye on closings and delays through the weekend and get the latest forecast videos as the forecast evolves.