Waves of heavy snowfall swept the central Plains Wednesday. By late evening, widespread 4 to 7” totals were down with a good deal more is expected to fall. Storm accumulations are to top a foot and may reach 16" in some harder hit locations of Kansas and southern Nebraska—states expected to bear the brunt of the new storm's fury.
The Chicago area's most widespread snow accumulation of the season likely; 3 to 7-inch totals possible by Friday morning
The huge storm system was first picked up by computer models as it left the Japanese coast more than a week ago. Numerical forecasts at the time suggested a potentially significant winter storm would develop from it across the nation’s mid-section---and that's occurred. The system is predicted to lift from the Plains into the Midwest as a respectable snow-maker. The Chicago area is forecast to sit beneath the leading edge of a pocket of powerful of jet stream winds late Thursday night into Friday morning—a region of the atmosphere in which air is encouraged to ascend, cool and become saturated. It's a process which maximizes precipitation development and may well deliver Chicago and the greater metro area one of the broadest coverage and significant snow accumulations of the snow-challenged 2012-13 cold season.
A variety of snow-forecast techniques lend credence to expectations that as much as 3 to 7" may be on the way, falling most heavily late Thursday night into the opening hours of Friday. Were snowfall to carry over into the hours beyond sunrise, it could impact the Friday morning commute period.
Even Arizona hit by this storm's snows
The storm's Wednesday snows weren’t limited to the Plains. Sections of southern Arizona, typically home to to far warmer conditions, were whitened by a cover of snow and an unseasonable chill Wednesday.
Chicago's last 3" snow occurred more than a year ago
A snow accumulation in excess of 3" in the city proper would be the first to occur here since 3.5" fell nearly a year ago on Feb. 24, 2012.
Thursday’s lake effect flurries segue to "system snow" late Tuesday night
Flurries off Lake Michigan---not directly related to the storm---are likely to flutter to earth from time to time Thursday in lakeside counties. No more than a dusting is expected with them.
The heavier, more widespread "system" snowfall associated with the incoming storm is to develop toward midnight Thursday night and continue into mid-Friday morning, from all indications.
A warming atmosphere could mix Friday's lighter, far more occasional late morning and afternoon snows with drizzle
At that time, snowfall is expected to ease if not cease from time to time with little additional accumulation.
Storm’s impact on the central Plains far greater than Chicago; more than a foot of wind-driven snow expected hardest hit locations
Areas west of Chicago are to see the storm’s largest snowfalls. A wide swath of Kansas and Nebraska---possibly even sections of Iowa and northwest Missouri---may see snowfalls which reach or exceed one foot. Our in-house RPM computer forecast model is even generating local 16" totals in some areas of the central Plains.
Storm’s warm sector to generate severe weather south toward the Gulf of Mexico
The 2013 severe weather season is underway in the Deep South. This storm system's warm sector is to support powerful thunderstorms which may become tornadic on sections of the Gulf Coast from near Houston, Texas east to New Orleans and Mobile, Alabama.