Destructive Wind Storm Blasting Central U.S. With Rare Tornado Threat In The North – The Washington Post

Half of the Lower 48 faces a dangerous weather event Wednesday into the night as an extremely powerful storm system sweeps through the middle of the country unleashing damaging winds and, in some areas, tornadoes, dust storms and out-of-control fires. So severe are the conditions that the National Weather Service is calling it a “historical weather day.”

“The Central U.S. has never seen a December storm like this,” tweeted Bill Karins, a meteorologist for MSNBC. “Multi-hazard, life-threatening weather today.”

From New Mexico to Michigan, more than 36 million people are under high-wind warnings. Winds of 70 to 100-plus mph have already damaged structures, overturned vehicles, toppled trees and caused tens of thousands of power outages while contributing to hazardous ground and air travel.

Amid the high winds, blinding dust storms have swelled over parts of southeast Colorado and western Kansas, with wildfires erupting in the Texas and Oklahoma panhandles.

The threat of severe thunderstorms is historically high in the zone from central Iowa to southeast Minnesota and multiple tornadoes have already touched down in Nebraska.

The Weather Service’s Storm Prediction Center declared a level 4 out of 5 risk for severe storms, warning of the possibility of “at least a few tornadoes” in the Upper Midwest. It has never issued such a risk forecast at this level in this area during December and if tornadoes strike Minnesota and parts of northern Iowa, it will be a first.

Twisters could even carve through areas blanketed in snow by last week’s storm.

Because of the exceptional winds and very dry conditions, the Southern and Central Plains is contending with a top-tier fire threat, the first “extremely critical” fire outlook the Weather Service says it has issued for the area in December.

All of this is occurring amid record-setting warmth in the central states, for the third time this month, helping to fuel the intensity of the extreme weather. Both Iowa and Wisconsin have seen their warmest December weather on record.

• Violent storms are sweeping through eastern Nebraska and Kansas with multiple tornado warnings in effect. Five tornadoes have been reported along with 89 instances of severe winds, with many gusts of 60 to 90-plus mph and reports of downed trees, overturned vehicles and some structural damage. Lincoln, Neb. clocked a gust of 93 mph. The thunderstorm complex is taking on the characteristics of a derecho, roaring east-northeast at breakneck speeds of 85 to 100 mph.
• A tornado watch is in effect for eastern Nebraska, northeast Kansas, northwest Missouri, western Iowa and southern Minnesota until 8 p.m. “Widespread damaging winds are expected, with peak gusts near 90 mph possible,” the Weather Service warns. “A mix of embedded supercells and smaller-scale circulations in the line will also pose a threat for tornadoes, with a strong tornado or two possible.”

• In Colorado, peak wind gusts reached 107 mph in Lamar, 105 mph in Broomfield, 100 mph at the Air Force Academy near Colorado Springs and 91 mph near Boulder Wednesday morning. Just northwest of Denver, a gust was clocked to 84 mph. Numerous gusts topped 70 mph in the state.
• In Kansas, Garden City and Dodge City gusted to 84 mph and Colby to 68 mph. The gust in Dodge City was its highest on record.
• Over 200,000 customers are without power in Colorado, Kansas, New Mexico, Oklahoma and Texas, according to PowerOutage.US.
• Fires have erupted in parts of the Southern Plains, including a blaze in Guymon, Okla. in the panhandle region, where some residents were told to evacuate. A second blaze, in the Texas Panhandle, was threatening the area around Skellytown.
• The high winds are causing air travel disruption at Denver International Airport with 485 delays and 145 cancellations.
• Several parked aircraft were damaged by high winds at Sante Fe Regional Airport on Wednesday morning. A radio tower was toppled in Taos, N.M.
• Dust storms have broken out in southeast Colorado and western Kansas, where a “wall of dust” was seen.
• Iowa has notched its highest December temperature on record. Des Moines reached its all-time December record, hitting 74 degrees. Dew points, an indicator of moisture and humidity, rocketed to record levels in the state. High temperatures and dew points fuel severe thunderstorms.
• Wisconsin matched its highest December temperature on record, with Boscobel hitting 70 degrees.
• Temperatures are nearing or surpassing record highs from Texas to Michigan. December monthly record highs have fallen in Omaha and Cedar Rapids in addition to the numerous locations in Iowa.

Already ripping at the ridge tops in the Rockies on Wednesday morning, winds will quickly ramp up into the day farther to the east into the Plains. Gusts of 30 to 40 mph across the southern high Plains in the morning will increase to midday gusts of 60 to 80 mph across southeast Colorado, portions of the Front Range and into adjacent areas.

Through the midday hours, winds may be sustained near or above 50 mph in places like Boulder and on the west side of Denver. Gusts in Boulder could reach 80 to 100 mph. Gusts over 100 mph are possible in the high elevations.

Further south, in Pueblo, maximum winds will be about 10 mph lower. Wind gusts of 70 to 80 mph are a risk across much of the southern High Plains.

By late afternoon and early evening, the strongest winds will move through Kansas and Nebraska, with widespread gusts over 60 mph. That wind core will translate to Iowa and other parts of the Midwest by late evening, followed by some weakening of the winds, but with many gusts of 55 mph toward the western Great Lakes.

Peak gusts are forecast to top 60 mph in almost all of Kansas, Nebraska and Iowa and parts of New Mexico, Texas, Oklahoma, Missouri, South Dakota and Wisconsin.

The level 4 out of 5 threat of severe thunderstorms from Storm Prediction Center is the second of recent days, following Friday night’s historic tornado outbreak in the Mid-South.

“Widespread severe wind gusts of 60-75 mph along with at least a few tornadoes are likely from late afternoon through this evening across the Mid-Missouri Valley to the Upper Mississippi Valley,” the Storm Prediction Center wrote. “Embedded gusts of 80-100 mph and a nocturnal strong tornado or two are also possible, particularly across western to northern Iowa and southeast Minnesota.”

Cities in zones of elevated risk include Minneapolis, Des Moines, Rochester, Mason City and Cedar Rapids.

The threat of significant tornadoes includes a 10 percent probability that one or more may be strong to violent.

The severe weather risk is unusually far north and west for this time of year. “The threat appears to be unprecedented for this region this late,” the Storm Prediction Center wrote.

In fact, the region at risk has seen no tornado activity in the modern record during December. In all of the winter months (December through February), only one tornado has occurred in Wednesday’s zone of highest risk.

The combination of the high winds and unusually dry conditions in the Southern and Central Plains means an exceptionally high fire threat. Any blazes that erupt could be difficult or impossible to contain.

“Very dangerous wildfire-spread conditions” are expected, the Storm Prediction Center wrote. The threat is expected to be greatest between late morning and midafternoon Wednesday.

The zone of greatest concern is from northeast New Mexico to southern Nebraska, including the northern Panhandle of Texas, the Oklahoma Panhandle and western Kansas.

In addition to the fire threat, dust storms are possible, restricting visibility.

Ahead of the windy storm, exceptionally warm air is expected to result in dozens of record highs from Texas to Michigan, by large margins in some cases.

Temperatures in the upper 70s are predicted in Dallas and Oklahoma City, with mid-70s around Kansas City. Temperatures in the 70s will surge into Iowa, with mid-60s in Chicago.

Some spots in the vicinity of Iowa could top the records by 15 to 20 degrees. In Des Moines, which is expected to hit 70, the previous record of 59 had already been surpassed at 6 a.m. Parts of Iowa will have temperatures 30 to 40 degrees above normal.

As the third round of record warmth in the eastern half of the nation, it will only add to a historically warm December in many areas. Human-caused climate change is increasing the intensity and likelihood of such warm weather.

The forecast surface map (below) shows an intense cyclone or zone of low pressure positioned across the Four Corners region of Minnesota-Iowa-South Dakota-Nebraska early Wednesday evening. The storm will be intensifying rapidly through the day.

The thin, curved, black lines are isobars (lines of constant pressure), and in this storm, they are becoming very crowded together — meaning the pressure gradient will be intensifying. This will drive exceptionally powerful, widespread winds feeding into the parent storm.

The “business zone” of this cyclone is the “warm sector” or region between the warm and cold fronts. Here, a low-level air mass of anomalously warm and humid air is surging northward from the Gulf of Mexico. This plume of buoyant air will be uncharacteristically unstable for mid-December and so far north, and is expected to provide the fuel for intense thunderstorms during the evening hours.

An elevated swath of warm and dry air over the upper Plains will add to the mix, which may render the air mass in parts of the warm sector quite volatile by enhancing the instability.

A key component to the severe setup is extremely strong low- and mid-level airstreams feeding into the deepening cyclone, in such a way that those winds veer or turn clockwise with altitude. This type of wind shear is conducive to rotating, solitary thunderstorms called supercells.

In the upper atmosphere, an unusually potent upper-level disturbance (shown above) will approach the Iowa-Minnesota region early this evening. The spreading apart or “fanning” of winds (as noted in the figure) will be particularly conducive to concentrating a pocket of strong upward motion over the region. The intense wind shear and strong dynamics associated with the storm system may create not only supercells but also bow-echo-like complexes with embedded tornadoes and downbursts.