SEASON’S FIRST STICKING SNOW ON THE WAY but likely to –COMMENCES IN CHICAGO 5 TO 7AM TUESDAY but likely to transition to wintry mix and rain at times the remainder of Tuesday—SECOND DISTURBANCE KEEPS CLOUDS AND WINTRY PRECIP GOING WEDNESDAY…..

Snow is to reach Chicago proper based on current modeling in the 5 to 7am time frame Tuesday; earlier south and west of the city–with precipitation likely transition back and forth between periods with a wintry mix of precip and others with ALL RAIN at times in many parts of the Chicago area the remainder of the day. Nighttime cooling Tuesday night could return precip to more snow than a mix. Northwest suburban areas stand the best chance of seeing more snow than rain during the day. And patchy accumulations can be expected in other part of the metro area including the southern suburbs. These accumulations aren’t likely to be huge–probably a covering on colder outdoor surfaces to perhaps an inch or two mainly west and northwest of the city Tuesday.

The first sticking snow of any season certainly garners attention because it stands out. When you haven’t seen snow for a while, you notice the white covering quickly. But the first snows of any season arrive with forecast challenges.

Some western sections of the Chicago area and of northern Illinois have seen a spell or two of very modest snowfall–measured in fractions of an inch. In the city and in immediate surrounding suburbs, flurries have fallen already–but they haven’t accumulated.

Last year, sticking snow didn’t occur in Chicago wasn’t to arrive for another month and a half. And when it occurred, it certainly didn’t overwhelm. All of 1.9″ last year on Dec. 28-29. It hasn’t snowed measurably here in Chicago since 0.2″ came down this past April 18 and before that 0.3″ March 11 and 2.9″ March 7. So, any sticking snow in the city in coming days would be the first in nearly 7 months.

Sticking snow Tuesday in the city would be the first of the 2022-23 season. Complicating early season snow accumulation forecasts–including this one–is the lingering warmth of Lake Michigan this time of year. At the moment, the AVERAGE Lake Michigan water temp is 51-deg.

East winds will blow in off these “warm” lake waters Tuesday. But as Tuesday progresses, the transport of “warmer” air off the lake will take temps above freezing, even if modestly. This, in turn, will shift the form of the precipitation wintry mix or all rain at times.

Early Tuesday, as precipitation with the incoming storm system gets going, the warmth of the lake is likely to be overcome lakeside early in the day by the mid 20 to low 30-deg dew points. Such low dew points set the stage for evaporative cooling and should be enough to allow precipitation to start as snow.

Clouds and precipitation are likely to linger at times into Wednesday. The portion of the Chicago area which may receive the greatest proportion of this system’s precipitation as snow is likely to be areas away from the lake–particularly northwest and north of the city. Current model probabilities put the chance for an inch or more of snow at 80% in sections of McHenry, Boone and Winnebago counties–and of 2″ there at 50 to 70%–while the chance for 1″ of snow drops off to 10 to 20% along Chicago’s lakefront and through southern suburbs and 2″ snowfall probabilities are put at 5% or less.

A SECOND DISTURBANCE rides into the Chicago area Wednesday which keeps clouds and some sporadic precipitation going then.

AN ENTIRE GRAPHICS PACKAGE FOLLOWS–Including forecast panels precipitation panels which enable you to follow how the incoming system’s snow and wintry precip is to sweep into and across the Chicago area–and also, some early estimates of potential snowfall. Also included are the National Weather Service WEATHER PREDICTION CENTER blended model snow accumulation probabilities and panels from my NWS Chicago colleagues covering the incoming winter storm system.