A powerful storm system will track into the region early Wednesday before shifting to the east, passing to the south of Iowa. To the north of this track, widespread precipitation will overspread the state, changing to snow in the early afternoon.
Today, an upper-level low pressure system with an associated deepening surface low will shift east into the region. Alongside this will be a boundary that will drape itself across the central part of the state, allowing for a large gradient of temperatures from the northwest to southeast. High temperatures today will be in the low 30s in the northwest to the upper 60s in the southeast. It will be a tale of two halves indeed with temperatures dropping throughout the day north of Interstate 80.. while increases will be seen to the south.
Here is how the timeline today is expected to go. By noon, the state will likely be overtaken by widespread-to-scattered showers and thunderstorms. This activity will increase from north-to-south through the morning hours. By noon, a gradual transition to all-snow should begin occurring in northwest Iowa. Snow should be kept confined to areas along and northwest of a line from Forest City to Sioux City through the 3:00 p.m. hour. By evening, the changeover from rain-to-snow will push farther southeast… overspreading moderate-to-heavy snow across the warning area.
To the south, scattered showers and thunderstorms will linger. Some of these storms may be severe with strong shear and modest instability present. Moisture is a bit lacking this far north with cold temperatures… which will hinder the overall threat. Nonetheless, with some of the elevated cells, an isolated large hail or damaging wind report cannot be ruled out. A marginal risk of severe weather does exist for the far southern parts of the state for this reason. However, the majority of this severe activity should be kept to the south where an elevated risk of severe weather is in place.
Models continue to improve as far as the track of the storm is concerned. Most of the suite has settled on a northwest track consensus, rather than the southeasterly one that the European ECMWF was suggesting a few days ago. With only slight variations in regards to where this will setup, much more confidence can be injected into the forecast. Amounts are still a bit iffy with some wild cards existing – for example, where convectively-enhanced snow bands will setup and how intense these will be, or how soon rain will changeover to snow in the morning in the north. These can have drastic impacts on a forecast. However, like all other modes, we are slowly becoming more confident in what is going to occur in that case. Just keep in mind that some totals may be locally higher here and there.
Currently, we are expecting the heaviest of snow to the north and northeast of the state, around the Rochester and La Crosse area. However… eight-to-twelve inches are still expected from central Wisconsin through southeastern Minnesota and into far north central Iowa. One of the adjustments with this package includes that band being expanded slightly farther southwest into the state… including Mason City, Clear Lake, Garner, and adjacent areas. While the totals are expected to be higher to the north of this gradient, totals over eight inches are still possible here.
Five-to-eight inches remains expected for northwest, north central, and extreme northeastern Iowa. The higher amounts will be farther north. Sioux City will be looking at five inches while areas north of Mason City could be looking at up to ten inches or so. Don’t read into the specific amounts given too much, this is just a general at-or-around point. To the south of this, the cutoff line will be dense, with Prairie Du Chien looking at six inches of snow, while Dubuque will be at-or-under an inch. I believe most areas south of Interstate 80 will remain snow-free for the most part, though sleet is not out of the question here. The DSM metro could be looking at a dusting, though Ames could see one-to-two inches.
Aside from the heavy snow potential, one of the other bigger concerns revolves around the expected winds tonight. Sustained winds of 25-35 MPH with gusts to 45 MPH in some spots will easily create blizzard-like conditions across those areas. Visibility will be next to nothing in spots where the heavy snow rates and high wind gusts combine. Travel will be next to impossible in some spots tonight – please do not travel unless absolutely necessary.
A Winter Storm Warning is in effect for the northwest and north central counties of the state. A Winter Weather Advisory remains for areas to the south of these alerts. In the west, alerts will go into effect early this afternoon and remain until around daybreak Thursday. For areas to the east, alerts will go into effect this evening and remain until mid-morning Thursday. Keep in mind that blowing snow will remain possible through much of the day Thursday with 10-15 MPH sustained winds with gusts to 25 MPH.
Stay tuned to the Iowa Weather Network for the latest information.