2/16-2/18 Saturday Night - Monday Morning - Long Duration Accumulating Snow Event Update #2

We are continuing to monitor this expected snow producing system that is socked right in the middle of our active pattern across the Midwest. The large scale features  responsible for this storm system have led to model guidance remaining fairly consistent over the last 24 hours or so with the overall evolution so not much has changed regarding overall thinking. If anything, models have trended a bit snowier for some areas that are set to receive accumulating snowfall. Also, this looks to be a fairly long duration event, especially for those closer to Lake Michigan and some areas could see continuous snow for nearly 24 hours out of this system. 

I dig into the latest details below as we continue to draw closer to yet another winter weather producing system...

As mentioned in previous posts regarding this system, it has continued slowly down the west coast over the last day or so and has finally come ashore southern California this evening and will now begin its trek eastward across the Four Corners region overnight tonight and through the morning hours tomorrow. It will then eject out into the plains later in the day tomorrow, leading to the development of an area of low pressure across the southern plains. 

This system will be more driven by the area of low pressure centered around 850mb, or 5,000ft off the ground and this is also the level where the strong warm air advection will be occurring, shown in red on the image below. As previously talked about, this will be one of the main drivers of the widespread area of snow developing across the plains to our west on Saturday evening. 

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Now time to get down to the specifics on timing...snow will develop to our west during the evening hours tomorrow and will make steady progress eastward into Iowa and Missouri during the late evening and overnight hours. After midnight tomorrow night, snow will move into portions of western and northwest Illinois, before continuing eastward into the rest of northern and central Illinois by the early morning hours. It then looks like it will snow continuously all day on Sunday and into the evening hours. The loop below is a long loop (spanning 39 hours), showing the entire evolution of this snow event, beginning at 3pm tomorrow and ending at 6am on Monday morning. You can initially see the snow developing across the the plains and moving eastward into our area by early Sunday with snow remaining over portions of northern and central Illinois for nearly 18 to 24 hours, making this for a very long duration event. 

 Lastly before we get to expected snow amounts below, I just wanted to briefly mention that surface temperatures will be rather cold, especially across the northern part of the state when snow begins on Sunday morning, leading to snow sticking and accumulating fairly easily after it begins. It will be in the mid 20's when snow begins across northern Illinois and in the upper 20's across central Illinois. 

Below is our latest thinking on expected snowfall amounts from this system and we will continue to update this map as we draw closer to the event beginning.