Good Tuesday morning all! The Chicago area in the the midst of a jarring meteorological move from Mondays 53-deg high (even some readings which moved to within 2-deg of 60 in parts of the area)--the warmest temps in over 3 months, to the brink of a winter storm--one which threatens high winds and the potential for a significant snow accumulation Tuesday night and early Wednesday. The morning commute period Tuesday is NOT to be affected. But a deterioration in travel conditions is to occur expeditiously late today and/or this evening and the strengthening storm could have an impact on Wed mornings commute, though snowfall will be tapering to more scattered lake effect snow showers or flurries in the high winds Wednesday. Blowing and drifting snow could become a problem after a switch to snow later tonight. The complicating issue with this storm--the wildcard if you will--is to be the speed with which the storms precip moves from the liquid phase, with which it may begin Tuesday evening--to all snow. The environment in which this system is to intensify and the track its to follow across downstate Illinois and Indiana, threatens a classic heavy snow in the Chicago area. At present, a blend of all available models and other snow forecast techniques supports widespread 4 to 8 accumulations from Chicago and its immediate suburbs south--lighter amounts as you travel north toward and beyond the Wisconsin state line. Embedded thundersnow is a distinct possibility--and its in areas affected by these thundery bursts of snow, the greatest accumulations may occur--some approaching 10. The storm spins up at the surface between two jet stream speed maxima--a configuration which lifts and cool air to condensation on a large scale. And the incoming flow of moisture is impressive. A tightening pressure gradient between the storms low pressure and a substantially higher pressure to the north, sets the stage for powerhouse winds, likely to gust to 40 mph or higher at time later tonight. Northeast winds will begin strengthening slowly Tuesday afternoon and should be roaring late tonight into Tuesday. Our graphic feature and WGN Chicago Weather Center blog address our thinking on this system and well keep you posted with updates here and on our WGN broadcasts during the day. For my fellow weather enthusiasts and geeks who like to get down to the nuts and bolts of this storms structure, Im posting our latest high resolution RPM models latest take of potential snow accumulation, the NWSs Weather Prediction Center super-ensemble depiction of the 40%+ probability of 4 or more snowfall, the latest surface map and a snapshot from the Weather Services 7am Wed surface map, a precipitable water forecast (depicting the storms moisture inflow), two jet stream depictions, illustrating the 30,000 ft and 18,000 ft.-level wind maxima in a classic Uccellini-Kocin coupled structure (i.e. lift on the right rear entrance region of the northern speed max and on the left front exit region of the southern jet streak and the latest 4km WRF models forecast of potential snow accumulation. Heres a link to my WGN-TV Chicago Weather Center blog posting: blog.chicagoweathercenter/2014/03/11/areas-mildest-surge-in-over-3-months-monday-sets-the-stage-for-a-blustery-spring-storm-cold-rain-and-sleet-to-shift-to-heavy-wind-driven-snow-tuesday-night/
Posted on: Tue, 11 Mar 2014 14:18:39 +0000
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