So far everything continues to point towards an early spring winter storm. What first started this morning on the southern California coast quickly moved northeast through the Rocky Mountains and as of 5PM tonight it continues to track east southeast through the central plains. This is a big reason as to why this system has been shifting a lot, due to it not being on land for a longer period of time. Pictured below is the latest analysis of the low that will bring our wintry system.
This low pressure will slowly move across the plains through Missouri overnight, eventually being near St. Louis by the morning hours Saturday pictured below.
Ahead of the low pressure, precipitation will continue to develop slowly to the west. Eventually this system will strengthen mainly late tonight through tomorrow morning. Current radar at 7:30PM shows precipitation developing across the central plains ahead of the low pressure. Rain and snow will slowly move into portions of western and northwestern Illinois late tonight and through the overnight hours.
Above is a simulated model suggesting precipitation across the are at 7AM Saturday. Much of the heavier precipitation will fall in the overnight hours. Below is another simulated model suggesting precipitation falling at 10AM Saturday.
As mentioned, this system will likely strengthen overnight into tomorrow morning hours setting up a heavy snowfall band. That area has been shifting ever so slightly to our south since the beginning of our discussions on Wednesday. The latest trends continue to shift the system slightly south putting heavier snowfall bands into portions of eastern Iowa, and across Rock Island, Henry, and Bureau counties.
Understand that this system is still a few hours out, and it may continue to shift a little further south, but models are coming together more and starting to agree with placement of that band. As you can see from the picture above, there is a very sharp cutoff in this system, and I wouldn't be surprised to see the cutoff become more sharp.
With that mentioned, we believe much of the Sauk Valley will still be impacted by this winter storm, mainly those who reside in Whiteside county will likely see more snow accumulation than those in Lee county. For those in Whiteside county, we will likely see 2" of snowfall area wide. Some areas will likely pick up more (as of current trends) around 4". Let's flip over into Lee county where less amounts may be seen though, especially in portions of eastern Lee county. In far eastern Lee county trends have been favoring 1-2" at least, those in central Lee will likely see 2" at least, and those in far western Lee county may pick up 2-3" at least.
Snow is likely to begin around Midnight across Whiteside county and then slowly move to portions of Lee county. Again, the strongest part of this system which will bring heavy precipitation will arrive overnight into the early morning of Saturday. Expect the precipitation to end Saturday afternoon to late evening (west to east respectively).
We still see a few uncertainties within this system. The big uncertainty is that this system may continue to change overnight and we may see the cutoff line sharpen across the northern areas. We do expect impacts to our travel hazards during this system as we go through tonight and through Saturday.
Visibility will be reduced due to overall strong winds gusting over 30MPH, a few slicks spots will be possible especially in the heavier snow.
The Winter Storm warning continues to be in effect until 7PM Saturday a seen above. Looking ahead, we'll see some major improvements in our week ahead in terms of temperatures. Much of the snow will be melting and many of us won't see it by the end of Sunday. Overall, we continue to see warming temperatures through this week and into next weekend.