ST. LOUIS — A Winter Storm Watch is in effect for the entire St. Louis area for Saturday night into early Monday morning.

A fast moving system is moving through the middle part of the country Thursday afternoon. That will allow in even colder air for the upcoming weekend.

The energy that will fuel our weekend winter storm is in the Pacific Ocean Thursday evening, more than 2,000 miles from St. Louis.

With colder air filtering in and this potent system coming in from the west, the stage is set for our major winter weather impacts. 

By late Saturday night into early Sunday morning, snow and a wintry mix are expected to develop across the region. While initially starting as snow in St. Louis, there will likely be a transition to or mixture with sleet for most of the metro area after daybreak Sunday. Farther south, the sleet will change to freezing rain. The glaze of ice over our southern counties could cause some power outages as trees and power lines may be pulled down due to the weight of the ice.

During the day on Sunday, wintry precipitation could be heavy at times. Gusty winds may create reduced visibility where snow is falling. Right now, it seems as through freezing rain, sleet and snow are all likely as we remain on the cold side of the system through the duration of the event with all snow more likely north and lesser amounts of snow but more freezing rain and sleet south. 

Based on the latest guidance and past experience, areas that see mostly or all snow during this storm will see more than a foot of snow. The transition zone, which is generally along Interstate 70, will see from four to 12 inches of snow and sleet accumulation. 

Farther south, sleet and freezing rain will dominate. Significant icing with upwards of a quarter to a half an inch of ice accumulation can be expected along and south of a Rolla to Farmington to Carbondale line. This could cause power outages. Up to three inches of sleet and snow will accumulate as the system pulls away Sunday night and the freezing rain transitions back to sleet and snow. 

Confidence is fairly high in this system having a significant travel impact for Sunday into Sunday night. Travel will likely be disrupted into Monday morning. After the wintry precipitation exits Monday, road crews should be able to make progress on clearing the ice and snow from the main roads. Secondary roads may be sloppy into Tuesday and Wednesday.