Weather Alert Day: Snow accumulating on roads Saturday morning, inches of accumulating snow and brutal cold forecast through the weekend

UPDATES:

Snow has begun to fall in Columbia, and reports are trickling in from around the region. A late-night weather balloon launch from the University of Missouri on Friday revealed less dry air than some forecast models had previously indicated. This is likely why snow onset has started on the early side of our initial onset timing windows. Still, it's been a slow start for accumulations, and we are now seeing snow pick up the pace as dry air has largely been saturated. Roads have become a bit more dicey since 8 a.m. Accumulations of 1 inch by noon, and possibly 2 inches by 5-7 p.m., are realistic expectations. It's important to remember that this is just round #1, and we are still on track for more impressive totals on Sunday.

A winter storm warning is now in effect for most of Central Missouri as heavy snow is increasingly likely this weekend. A winter weather advisory is also in effect across Northern Missouri.

A cold weather advisory remains in effect areawide for below-zero wind chills throughout the weekend.

The ABC 17 Stormtrack Weather Team has issued a Weather Alert Day from Friday morning through Monday morning as dangerous cold and heavy snow are expected over the weekend.

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, potentially impacting Mid-Missouri with cold and measurable snow.

Heavy snow is becoming increasingly likely as the forecast comes together. The storm is just coming ashore on the West Coast and has been sampled by reconnaissance planes to potentially improve forecasts across the country.

Dry air at the lowest levels of the atmosphere could eat away at snow as it arrives Saturday morning, but this is becoming less of a factor in the forecast. On the flip side, intensely cold air will create higher snow-to-liquid ratios, making snow accumulation more efficient.

FUTURETRACK:

It's going to be cold all weekend, likely colder than it has been all season. High temperatures on Saturday and Sunday will likely remain in the single digits to around 10 degrees. Wind chills will be coldest on Sunday night into Monday morning with readings between -15 and -20.

Snow showers are expected to begin across southwest Missouri late Friday night, spilling into Mid-Missouri before dawn Saturday and becoming widespread throughout the day. A short break in snowfall is possible late Saturday, but another round of widespread snow will quickly follow into Sunday morning. Snow finally ends near or just after noon on Sunday.

HAZARDS/IMPACTS:

Snowfall amounts will be highest along and south of I-70, especially around the Lake of the Ozarks and I-44, closer to the center of low pressure in Arkansas.

Totals continue to inch higher with newer forecasts. The probability of exceeding 6 inches of snowfall is now at or above 70% along and south of I-70, including Columbia and Jefferson City. We're most uncertain about totals in the far north, where drier air could eat away at snow for longer, with a range of 3 to 6 inches possible.

Our greatest confidence is in extreme cold; with frozen pipes, car trouble, and frostbite possible with prolonged exposure this weekend. Snowpack will extend the cold through Sunday and early Monday, with Monday morning possibly the worst now as high pressure slides over the area. Wind chills could be below -20 degrees if the coldest forecast sticks on Monday.

Roads will be quite slick with very low visibility between Saturday morning and Sunday afternoon. Treatment could be tough through the weekend 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.