A powerful storm of Pacific origin is brewing over the Western US Thursday. The storm will produce a narrow but long swath of heavy snow and ice stretching from the southern Plains to the Great Lakes. This same storm system is also expected to produce a severe weather outbreak over the South-Central US. The storm will be so dynamic that parts of the Southern Plains will be threatened by both severe weather and winter weather.
Spring-like warmth and copious quantities of moisture are expected to pour from the Gulf of Mexico into the Southern and Central US Friday as low pressure intensifies over the Arklatex. Arctic cold over the Northern Plains will act like a wall against the oncoming subtropical air mass. Where the warmth encounters no hurdles, torrential downpours from thunderstorms will produce areas of flash flooding and river flooding. In the South-Central US, these storms will become severe, capable of producing violent tornadoes, hurricane-force wind gusts, and golf ball-sized hail.
A much whiter scenario is in store for areas north of this wall of arctic air. The air mass pouring from the Gulf of Mexico will be forced to glide over the dry cold below. This will produce heavy freezing rain close to the boundary of the air masses transitioning to heavy snow with increasing distance.
Wintry weather will first develop just do the north of the developing low Friday afternoon in the form of light to moderate snow in Nebraska, eastern Colorado, and northwestern Kansas. A narrow area of freezing rain is expected to develop just north of the warm frontal boundary in northeastern Kansas and northwestern Missouri.
Low pressure will rapidly intensify throughout Friday night and Saturday as the Pacific trough supplying the storm’s energy inches further east. The approach of its vigorous jet stream will amplify the influx of moisture and warm air from the Gulf of Mexico. This will simultaneously push the low pressure system toward the Great Lakes while expanding and elongating the swath of snow and freezing rain.
By Saturday morning, a narrow corridor of heavy freezing rain will have made roadways a skating rink along an axis from roughly Flint to Oklahoma City. The corridor of heavy snow will be located just north and west of the freezing rain. Given the low’s northeastward trajectory, many cities across the Southern Plains, Mississippi Valley, and the Rust Belt will find precipitation transitioning from heavy rain to heavy snow. The transition will be particularly extreme in the Southern Plains of Oklahoma and southeast Kansas, where the swath of heavy snow will be falling just hours after being threatened by severe thunderstorms.
Many places will experience winter weather but only a narrow swath roughly 100 mi wide will face severe impacts. These are the areas that remain just north and west of the boundary between arctic dry cold and subtropical wet warmth throughout the duration of the storm. They could receive up to a crippling 1″ of ice accretion on trees and power-lines and over a foot of heavy wet snow.
Numerous metropolitan areas reside along the fine line of severe wintry impacts including Cedar Rapids, Milwaukee, Grand Rapids, and Flint. Impacts include wind-whipped snow-fall locally up to 16″ and/or ice accumulations of 0.5″ to 1″. Both impacts are likely to result in widespread power outages and make for treacherous travel. Lighter but still disruptive winter impacts are expected over a larger area, including cities like Oklahoma City, Kansas City, St. Louis, Des Moines, Green Bay, and Chicago. Snowfall on the order of 3-6″ and ice accretions of under 0.25″ will be standard here.
Snow and freezing rain are expected to end early Sunday morning as the low pressure system ejects into Ontario. Widespread road closures, flight delays, and power outages can be expected in the storm’s wake throughout the hardest-hit areas. Unfortunately, parts of Wisconsin and Michigan may have to confront more snow next week.