Our winter storm is continuing to steadily take shape this afternoon with the heart of the upper level low still well to our southwest across New Mexico and ejecting out into the southern plains. The worst of the winter weather will get going across portions of the state later tonight and overnight. I dig into the latest below on what to expect going forward along with expected amounts of both snow and ice.
Taking a look at a mid-level water vapor image along with radar, we can see our main weather system (circled in orange) is still well to our southwest. A wide open Gulf of Mexico ahead of it coupled with increasing large scale ascent from the upper level system over New Mexico and strong warm air advection has led to widespread precipitation (in red) developing since this morning across the southern and central plains and into portions of the Midwest. This area of precipitation will continue east and northeast into Illinois by this evening.
The areas of convection across the plains (thunderstorms) will continue northeast into portions of the state later tonight and overspread much of the state by the mid-late evening hours, as you can see in the loop below. Everyone outside of northwest Illinois will remain mostly if not all rain with this round of precipitation. The animation below runs from 2pm this afternoon till 9pm tonight, showing the increase in widespread precipitation into much of Illinois.
As mentioned above, northwest and north central Illinois will be the only areas to be dealing with wintry precipitation late tonight and into the morning hours tomorrow. The image below shows this quite nicely with much of the area seeing plain rain given temperatures above the freezing mark.
By tomorrow afternoon and evening as the surface low strengthens pulling in colder air, a band of snow looks to develop from southeast Missouri on northeast into western and northern Illinois from the afternoon on into the late evening hours, as shown in the animation below. Ahead of this, expect continued chances for sleet and freezing rain across northern Illinois during the morning and afternoon hours ahead of this feature. When the snow does arrive later tomorrow and tomorrow night, outlined areas could see a several hour period of heavy snow with even the chance for some thundersnow given the impressive dynamics. Also, with falling temperatures and strong winds out of the north and northeast, travel conditions could become very problematic, including the threat for blowing and drifting snow. The surface low going over Indianapolis, as shown below, is usually a favorable track for good accumulating snow across much of northern Illinois.
Below is our latest thinking on snowfall and freezing rain (ice) totals through the entire event.
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