Decoded Science and the Weather Channel agree on the naming of Winter Storm Yona, though much of the weather that this storm will produce would normally be associated with spring and summer.
A high risk of tornadoes will cover a wide area today, and five inches of rain has already fallen on parts of Missouri.
Still, this is a winter storm which will deposit over a foot of snow in parts of the upper midwest and impact the city of Minneapolis.
Winter Storm Yona Nearly A Clone Of Young Xenia
Winter Storm Yona will follow in the path of last week’s storm, Young Xenia, with some subtle but important differences. The cold air, and thus the snow, will nudge a little farther south; and the flow of air from the Gulf of Mexico is warmer, wetter, and more extensive, increasing the level and aerial coverage of the tornado threat.
Yona’s Band Of Heavy Snow
More than six inches of snow is likely in Minneapolis, where the precipitation will start as rain; Amounts of a foot or more will occur in northeast Minnesota, northern Wisconsin, , and part of U.P. Michigan.
The snow will be the heavy, wet kind with high moisture content that is difficult to shovel, and where the snow mixes with rain along the southern boundary of the heavy snow zone, winter will end in a slushy mess.
Winter Storm Yona’s Tornado Threat
Southerly winds from the Gulf of Mexico at the surface bringing warm, humid air all the way north to Illinois, coupled with a moderate mid-level dry stream from the west at higher altitudes, set the stage today for tornadoes from eastern Texas and northern Louisiana to Illinois, including all of Arkansas and Missouri.
The greatest threat will be this afternoon, as daytime heating combines with a cold front to cause lifting of the potentially unstable air.
On Friday, the system will lose some steam, and the tornado threat, though present in Georgia, Alabama, and Tennessee, will diminish considerably.
Yona Will Produce Flooding
Because the air is warmer and holds more moisture as the days get longer and the sun climbs higher, the rain in the warm sector of Yona will be copious. Five inches has already fallen in parts of Missouri, and similar amounts could be widespread in the zone of high tornado probability. Missouri has experienced flash floods, and there could be more as Yona moves east.
Yona Produces Four Kinds Of Frozen Precipitation
If variety is the spice of life, then Yona is spicy, indeed, containing all four major types of frozen precipitation: snow, sleet, freezing rain, and hail. In addition to the snow on the northern side of the storm, narrow bands of sleet and freezing rain will occur near the changeover to rain.
Where the warm air has overrun the cold, raindrops can freeze before they hit the ground (sleet), or on contact with the ground (freezing rain). In the unstable air, hail is produced when frozen raindrops are carried up and down in the frequent updrafts, each time accumulating an additional coating of ice. Golf-ball-sized hail has already been reported in Texas.
What’s Next? Can We Make It All The Way Through The Alphabet?
Though winter-type storms can form at this time of year, even into May, they become increasingly rare as the systems warm to produce more rain and less snow.
The seven-day forecast indicates a storm moving through the Ohio Valley next Tuesday. Right now it is questionable whether the air will be cold enough to support a snowstorm worthy of the ‘Z’ name, Zephyr.
After that, a less vigorous polar vortex will retreat into Canada, and the winter storm season will come to an end. Hallelujah, and good riddance!
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