Strong winter storm, but with unpredictable snowfall, on its way to Eastern Iowa

Iowa may get a white Christmas, but it’ll be the coldest one the state has seen in years.

The National Weather Service placed the Corridor on a winter storm warning between 6 p.m. Wednesday until 6 a.m. Saturday in advance of a major winter storm bringing high winds and, with them, a bitter wind chill of some 30 to 40 degrees below zero.

Snowfall totals remain too unpredictable — the latest guess is 4 to 6 inches in Cedar Rapids and 3 to 5 inches in Iowa City — but weather experts say the freezing temperatures and possibility of blowing snow mean much more, leading to treacherous driving conditions and threatening circumstances for venturing outside.

This storm could qualify as a “bomb cyclone” — in which the barometric pressure inside drops rapidly — or “bombs out” — and the rising air is rapidly replaced by air around the storm, leading to a violent system that could threaten tree limbs and power.

“While this is going to be a strong storm, that doesn`t necessarily mean that we are going to see very heavy snowfall,” the weather service said in a forecast discussion. ”With this strong of a system, we can expect strong gradient winds. If we get snow that is fluffy enough and blows around easily, this can lead to near blizzard conditions.“

The lowest wind chills could bring the temperature down to -20 to -40 degrees or colder beginning Thursday and lasting into at least Christmas morning.

The projected normal low for Christmas Day is currently 5 degrees. Iowa hasn’t had a single-digit high on Christmas Eve or Christmas Day since 2000.

Because of the extreme cold, local public works departments can do little to prepare roads for the weather to come. The cities of Cedar Rapids and Marion said they will not be pretreating roads ahead of the storm.

“We anticipate very cold temperatures after the completion of snowfall. This will make salt less effective,” Cedar Rapids Assistant Public Works Director Michael Duffy said. “Flake chloride is added to salt/sand mix to increase the effectiveness of materials. We do anticipate using this material to break any bonding between snow and pavement at the completion of snowfall during clean up.”

Linn County Secondary Roads Operations Superintendent Jerad Kelley said sand on the road is to provide “grit for traffic” until salt and chloride can work to melt snow and ice.

“A general rule of thumb to note: If the temperatures get below 10-ish degrees and the sun is not out, the salt and chloride do not work as well and we rely heavily on the sand in the mixture to provide grit,” he said. “Another good rule of thumb is that salt works best between 35 degrees down to 10 degrees, but its effectiveness decreases as the temperature decreases. The reason we put calcium chloride in the mix is to help melt snow/ice to temperatures below 10 degrees. There are claims that it can work as low as -25 degrees, but my experience says that is not very accurate.”

The National Weather Service said there is a good chance that Cedar Rapids will experience “moderate to heavy snow,” which is defined as 4 or more inches, during the storm. “Impacts will be similar statewide due to significant blowing and drifting regardless of who sees the highest accumulation,” the weather service reported.

The weather service said the snow will begin in the north and west Wednesday, spreading across Iowa by Wednesday night and into Thursday with it ending east late Thursday night.

Significant blowing and snow and potential blizzard conditions will begin Thursday and last into Friday. Forecasts say there is a potential for 40 to 50 mph wind gusts.

Across the country, winter storm watches have been issued for 32 million people.

The conditions also will affect holiday travel this week. Eighty percent of seats are full on flights from The Eastern Iowa Airport through the weekend, but the storm threatens flight cancellations across the country. Thursday is expected to be the busiest travel day, according to the Federal Aviation Administration, with 47,554 scheduled flights.

Many airlines, including American Airlines, have begun issuing travel waivers, allowing passengers to reschedule flights with no change fees. Those traveling to or from The Eastern Iowa Airport on American are eligible for the waivers, according to American Airlines’ website.

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