A powerful storm system has developed to the west Thursday morning and will continue to strengthen throughout the day.
Snow has already started across the Dakotas and Nebraska. Rain will develop across southern Iowa this afternoon as the Low pushes farther to the northeast. This rain will lift north along a warm front during the evening hours. Thunderstorms will be possible after sunset Thursday night, with a marginal risk for severe weather in place across the state of Iowa. This means that one or two severe storms with strong winds and heavy rain are possible.
In addition to the marginal risk for severe weather, a Blizzard Warning is also in effect for northwest Iowa on Friday.
Snow will start in the northwest corner of the state around midnight. Because convection is a strong possibility with this system, thundersnow will be possible in this area. This will allow for heavy pockets of snow to form. 8-12″+ is likely from Sioux City to Fort Dodge to Mason City. Winds are expected to be between 20-25 mph during much of the day Friday which will create blizzard conditions in northern Iowa, travel is not advised.
Warmer air will dominate south of Hwy 20, so a sharp cutoff in snow totals is likely. Rain will continue to fall through the early hours of Friday with a change-over to snow around the morning commute. Plan accordingly as roads are expected to be very messy, especially to the northwest. The majority of snow will accumulate in central Iowa after the lunch hour. 1-3″ is possible from I-80 to Hwy 30 with 3-7″ up to Hwy 20.