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Spring is up to its usual games....
An incoming storm is and will continue to push rain across the upper Midwest Saturday afternoon and evening, and with this rain will come a chance for some severe weather.
The storm prediction center upgraded parts of the area to MARGINAL (level 1/5) and SLIGHT (level 2/5) risks for severe weather this afternoon. There is a greater chance for severe weather towards the southeast (Floyd, Chickasaw, and Howard counties), and a minimal chance for severe weather towards the northwest (Freeborn, Dodge counties).
This chance comes as a potent warm front is pushing north across the Midwest on Saturday. Behind this warm front is significant heat and moisture to provide instability. A surface low pressure center will swing right along the MN-IA border late this evening, but the main severe weather threat will be before this time, when the low pressure center is pushing across the area this afternoon with maximum instability.
On top of this, winds are heavily curving in the atmosphere, with a strong jet stream from the southwest provide ample wind shear to ventilate and help spin up storms, especially to the southeast.
THREATS: The main threats on Saturday will be moderate flooding as rain totals could be around an inch, and strong winds / small hail associated with stronger thunderstorm cells.
TIMING: The severe weather threat will start 1-2pm in parts of Northern Iowa, and end this evening around 8-10pm, the best window for severe weather will be between 4-7pm. Rain will continue on/off throughout the night, and a wintry mix will move in early Sunday.
LOCATION: Slight Risk - Floyd, Chickasaw, Howard, and parts of Cerro Gordo counties. Marginal Risk - Hancock, Cerro Gordo, Worth, Mitchell, Howard, Mower, Fillmore, and Olmsted counties.
The placement of severe weather will be entirely dependent on how north the warm front makes it this afternoon and evening. A warm front that pushes even slightly further north then expected will expand the region for possible severe weather significantly. Some models do indicate a "triple point", where the fronts converge, moving through northern Iowa this afternoon. A triple point is typically a very favorable location for severe weather to occur. We will be tracking this all evening.
Outside of our area, there are greater risks for severe weather. An ENHANCED threat (level 3/5) is in place for all of nearly all of Illinois and eastern Iowa - including Waterloo just to our south. A MODERATE threat (level 4/5) is in place for far eastern Iowa and most of northern Illinois. There will be a significant threat for strong and long track tornadoes this afternoon in this area.