By Philip Joens, Des Moines Register
Des Moines could hit 70 degrees Wednesday and set an all-time record high temperature for December.
Iowa’s capital hit 69 degrees six times in past Decembers, as far back as 1889 and as recently as 2017. Wednesday’s forecast high of 71 degrees would set a new monthly high temperature record and smash the daily temperature record for Dec. 15 of 59 degrees set in 2002.
But the day will not be one to relax outdoors. Winds in Des Moines and Mason City could gust as high as 65 mph, according to the National Weather Service. Wind gusts will increase sharply in the afternoon and evening, according to the NWS.
UPDATE:Widespread power outages are expected in Iowa from windstorm with hurricane-force gusts
“It’s not the kind of day that you’re going to really be taking advantage of,” said National Weather Service Meteorologist Roger Vachalek.
A high wind watch — issued when winds are expected to be over 58 mph — will be in effect from noon Wednesday to midnight Thursday across much of southwestern, northern and northeastern Iowa. High wind watches are typically issued when there is no threat of severe weather, and are rare, Vachalek said. Since 2010 the NWS Des Moines office has issued just seven high wind watches.
Trees could be damaged and widespread power outages are possible, according to the watch.
Wind gusts between 35 mph and 50 mph will start early in the day, he said. The strongest winds will arrive in Council Bluffs around 4 or 5 p.m. Peak wind gusts may reach Des Moines by 6 p.m., he said. The storm will be moving at about 70 mph, he said.
Through dawn on Thursday winds will gradually slow, Vachalek said.
He stressed that the storm will be getting stronger as it moves up from Nebraska toward Lake Superior. Drivers with high-profile vehicles like semitrailers or tractors “are going to experience very difficult travel conditions,” Vachalek said.
On Wednesday there is a slight chance for severe weather across northwest, northern and central Iowa, Vachalek said.
“Any storm that’s going to be moving out there Wednesday is going to be moving quite quickly, we suspect,” Vachalek said. “So it won’t take much of a downdraft out of a storm to cause a high wind gust above 60 or even 70 mph.”
Conditions started to heat up Sunday when high temperatures rose from 42 degrees Saturday to 54 degrees Sunday. Monday had a forecast high of 56 degrees in Des Moines. Tuesday has a forecast high of 58 degrees.
A combination of a lack of snow cover and warm, dry air moving in from the west and southwest moving northeast will cause the warmer temperatures and windy conditions, Vachalek said. Snow typically reflects sunlight during daytime hours and allows the warmth from the earth’s surface to leave much faster.
But Des Moines has gotten just half an inch of snow so far this winter. Des Moines usually gets 5.5 inches through Dec. 12, according to the NWS. The latest into winter that Des Moines got its first snowstorm of 1 inch or more was on Feb. 2, 1989.
For the second straight winter a La Niña climate pattern — a natural cooling of sea water in the tropical Pacific Ocean — emerged. La Niña weather patterns affect the position of the Jet Stream and thus all weather across North America.
An NWS outlook predicted southeastern Iowa could have above normal temperatures this winter. But last year was a La Niña year and Des Moines got about 59 inches of snow, about 20 inches more snow than normal.
“Sometimes those can be cold and very snowy and other times they can be a little bit warmer and a little bit less snowy in the Midwest,” Vachalek said. “It’s not to say that the rest of this winter is going to be this mild. We could turn around and have colder temperatures in January and February.”
Philip Joens covers breaking news for The Des Moines Register. He can be reached at 515-443-3347 at [email protected] or on Twitter @Philip_Joens.