By Meteorologist Tom Skilling
Waves of rainfall associated with the third spring storm to sweep the Midwest and Chicago metro areas in under a week could generate the region’s biggest rain tally since late October.
A suite of computer-generated rain forecasts is placing Chicago area rain tallies in the 0.98” to 2.42” range. That’s quite a rain! An amount of more than 1.17 inches would exceed 2014’s highest tally to-date —the 1.16″ which fell on Feb. 20. It would become the heaviest total recorded here since 1.59” fell Oct. 30-31.
Heaviest rains to hit in two waves—the first overnight into Thursday morning; a 2nd Thursday night
The incoming storm system is to produce rainfall in a series of waves beginning Wednesday night.
The two heaviest periods of precipitation appear likely to occur Wednesday night into Thursday morning and again Thursday night.
The manner in which a storm system generates and distributes its precipitation is often extremely complex. Rainfall rarely falls homogeneously, occurring instead in bursts, the intensity of which can be dictated by features such as thunderstorms. Thundery downpours can concentrate heavy rainfall over the swaths of terrain they travel. These areas may receive considerably more moisture than surrounding areas.
Flood of warmth and moisture up and over chilly air here predicted to generate embedded thunderstorms
Thunderstorms are likely to occur with this developing weather system. The moisture fueling the storm is riding northward through 80-degree and warmer air within its southern flank.
Such warmth not only assures quite a supply of moisture, it also “destabilizes” (i.e. increases the rate at which temperatures fall with height), encouraging air to rise, producing towering thunderstorm clouds within the storm system’s precipitation shield.
Storm threatens to spawn major severe weather outbreak from Plains to areas downstate next 2 days; wind-driven snowstorm to lambaste corridor from Iowa to Minnesota, western Wisconsin and Upper Michigan
Outbreaks of severe thunderstorms are predicted within this storm’s warm sector while howling (and cold) northeast winds to the north of the storm center are to produce significant snows through areas from north-central Iowa north across the Twin Cities and into Michigan’s U.P.