Our system of interest is still out over the Pacific Ocean this afternoon and continuing to give computer model guidance fits regarding exact solutions for Sunday and into Monday, which seems to be the time-frame now for accumulating snow across portions of the state. The latest follows below....
As mentioned above, the system we are keeping an eye on continues to move its way across the northern Pacific Ocean today and will continue east before turning southeast before coming ashore California tomorrow evening. It is then forecast make its way into the Four Corners region by Sunday afternoon. After that, uncertainty still remains on the track and strength of this system.
By Sunday evening, there is good operational and ensemble agreement on low pressure developing across the southern high plains but the track it will eventually take later Sunday night and into/through the day on Monday is still uncertain, as you can see below. The track will determine what areas of Illinois will see accumulating snow.
As things now (which are subject to change given the remaining uncertainty) it looks like there will be to periods to watch for accumulating snow across portions of the state. The first will arrive Sunday afternoon and evening well out ahead of the developing surface low thanks to a period of strong warm air advection up and over the front. This will aid in precipitation developing across Missouri and downstate Illinois during the afternoon on Sunday. High pressure to the north will attempt to act as a wall and keep snow from coming northward but that is just one of several things that remains up in the air.
As the surface low comes northeastward, another period of precipitation, one that could feature a couple precipitation types, will move into portions of the state overnight Sunday and into the first half of Monday. This looks to be the second period of accumulating snow for some while areas further south could receive a mix or even all rain. Again....**we can't stress this enough**....it is still too early to nail down areas to expect all snow, accumulating snow, a potential mix area, or an area getting all rain.
We continue to outline an area that could be under the gun for shovelable snow later Sunday and into portions of Monday. Stay tuned for continued updates as we get closer and are able to pin down more specifics regarding potential snow amounts along with what areas will be most likely to receive accumulating snow.