THUNDER AND ICE....
A very complex situation will unfold across the Upper Midwest Monday and Tuesday. Warmth and thunderstorms on one side with a few tenths of ice on the other side. Winter Storm Watches have been posted in advance of this system.
Here are the latest advisories from NWS Quad Cities -
From the NWS Des Moines Sunday night into Monday -
And Monday night into Tuesday -
And from the NWS La Crosse -
Since these are Winter Storm Watches they will likely be upgraded to warnings or advisories Monday morning. There are still some differences in the track of the storm which will impact temperatures, precipitation types and amounts. There will also be two rounds of precipitation - on Monday and Tuesday.
Let's break it down. The storm will start to move into the state of Iowa Monday morning and moisture will be on the increase.
Now the exact track of this system will determine the temperatures. Check out the differences in the high temperatures on the GFS and European -
In Cedar Rapids the GFS has a high of 42 while the Euro has a high of 58 - an even bigger difference than what Terry showed in his earlier post. The solution likely falls in between. Regardless - with this warmth and moisture there will be some areas of heavy rain and even thunder. Both models do show some instability that would lead to some embedded thunder in the southeastern portions of Iowa and into Illinois an Missouri.
High moisture levels will also lead to the potential for heavy rain. There is uncertainty on where the heaviest of it sets up, but there will be some 1-2" totals. Here's the GFS and Euro respectively through the entire event (ending Wednesday morning)
Now onto the issue of ice. The north side of the low is where there will be colder air and more of a freezing rain event. There will mainly be a glaze Monday morning into Monday night with some heavier freezing rain Monday night into midday Tuesday. Here's the total ice accumulation on the GFS, European, NAM and 3km hi-res NAM:
3km NAM -
The two NAM models are much further south with the storm and the cold air. However, a lot of the snow melted away once again Sunday and I think this will send the storm track further north - more along the lines of the GFS and Euro. But there could be some decent ice accumulations, as high as 0.4 to 0.5". The heaviest of this right now running from SW Iowa to NE Iowa with central Iowa in the cross hairs. There will likely be changes and we will update you through the next 48 hours. What is certain is there will be slick streets starting late Monday morning through Tuesday afternoon.