Snowfall Expected in Central Iowa; Storm Forecast Tonight

Bryan Dijkhuizen

Today's outlook is another tangle of variables. Having exited to the east at H850 and presently over northern Wisconsin, the next upstream wave is over northeast Colorado and is forecast to drift east by the afternoon.

A modest zone of warm air advection will resume throughout Iowa by early afternoon, reaching its zenith in the late afternoon to early evening period.

The deeper moisture has been moved east of the area for the time being, but there is still a significant pool of H850 moisture accessible across the lower Mississippi River Valley and into the Gulf.

As the wave approaches, part of this will be drawn back northwest into an upper-level frontal zone over the region today, resulting in a drier atmosphere.

There are still a few questions that will influence the quantity of snow that falls this afternoon, the most important of which being where the most concentrated lift will be located and how severe a gradient will occur inside the boundary.

It looks like the heaviest snow will fall from approximately Creston to just near/south of Des Moines, and east to around Grinnell and other places east of the state capital.

Soundings indicate a mid-level weakening in static stability, indicating the possibility of bands from 3 p.m. to around 7 p.m. along that axis.

Most of the snowfall will fall between the beginning and finish of the afternoon rush hour, as a result.

Even though it is difficult to define the precise axis in these more rapidly evolving storms, precipitation quantities of about 0.10 to 0.15 inches will be highly believable along the axis.

As a result, snow ratios this afternoon and tonight will be in the 13 to 14 range, resulting in at least 1 to 2 inches of snow in that direction. Certainly, with visibility reducing to 1 to 2 miles and roads blanketed with snow, traffic disruptions are possible for a limited area of the region today, but they are not expected to be widespread.

The storm will move eastward tonight, with clouds gradually diminishing later in the evening, mostly across the southern United States.

Highs today will be chilly and in the teens north of the border and the mid to upper 20s south of it, while lows tonight will be in the single digits north of the border and in the mid to upper teens south of it.

A further lee side trough will develop by tomorrow, bringing with it the return of southwest flow aloft and the rising of H850 temps by late afternoon.

With some sunshine predicted, high temperatures will rise to the upper 20s in the northeast and the mid to upper 30s in the south.

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