NEWS

Weather to deteriorate — wind, rain and sporadic thunder to sweep into Chicago with autumn storm


Multi-day rainfall through this weekend looks to be heaviest in 3+ months


WGN WEATHER HEADLINES


FROSTY MORNING AWAY FROM THE CITY TUESDAY

Chicago logs its coolest morning minimum temp since early May

  • Temperatures bottomed out at 42 at O’Hare and interestingly 40 at Midway — the coolest city temps of the season and in the 5 months since early May this past spring.
  • It’s not every day Midway’s low temp comes in below O’Hare’s — but it happened Tuesday morning. The normal Chicago low temp Oct 10th is 48 degrees, and a check of weather records back to 1871 shows fewer than a third of Oct 10s have been as cool in the city. Just 44 of the past 153 years have produced a minimum temperature of 42 degrees or lower. This morning’s 42 at O’Hare makes it the coolest Oct 10 low temperature in 8 years since 2014.

A CLASSIC AUTUMN STORM SPINNING UP IN THE DAYS AHEAD

  • We have a classic autumn storm spinning up in the days ahead — the product in part of a powerhouse jet stream-level WIND MAX analyzed this (Tuesday) morning at 190 mph at the 34,000 ft. level over the eastern Pacific — and headed toward the West Coast. Such upper air wind maxima encourage air to rise the through the atmosphere, cooling it to saturation and generating clouds and precipitation in the process. The ascending air also drops barometric pressures at the surface which, in turn, encourages winds to develop which increases the flow of moisture into the resulting storm system.
  • What you see in the animation posted here is a graphic depiction of this process as we move forward in time. Moisture can be seen sweeping north out of the Gulf of Mexico over time and into the developing autumn storm.
  • The resulting autumn storm system appears likely, based on model forecast guidance, to generate a SOAKING RAIN in Chicago and over a wide swath of the Midwest the back half of this week and over the coming weekend with initial model rainfall projections suggesting TOTAL RAINFALL in the Chicago area may be measured IN INCHES.
  • Note how all that moisture sweeps into Chicago and the Midwest in the late Wed through Friday time frame. And sporadic rains are likely to extend beyond this work week into and through the coming weekend. MORE TO COME ON THIS SYSTEM……

PRECIPITATION CLASSIFICATION FOR OCTOBER-SEPTEMBER 2023

  • You can see why Mississippi River water levels have been sub-par — precip in the region has been BELOW NORMAL. Meantime, check out the region of ABOVE NORMAL TEMPS across California and reach into the central Rockies — though flood generating in parts of that region at times, an overall godsend in a region mired in horrific drought conditions for years. All eyes will be on the precipitation trends in the West given the presence of a strengthening El Niño ­­­in the equatorial Pacific.

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