Rainfall continues overnight before Wednesday morning clearing

FIRST, THE TUESDAY WEATHER HEADLINES 

–It’s likely to end up THE CHICAGO AREA’S HEAVIEST RAIN in 3 months—since 2.09″ fell July 23-24. 

–It’s going to get WINDY TOO with 30+ mph wind gusts locking in from the north and reaching GALE FORCE over Lake Michigan tonight and Wednesday. The energy transfer from the atmosphere to the lake surface will build formidable swell with offshore waves reach 12 to 16 ft which 6 to 8 ft. waves may crash on the Chicago shoreline by later tonight and into Wednesday 

–Model rainfall projections are amazingly consistent with the current late autumn storm system coming in between 0.97″ on the low end to as high as 3″ at a few higher end locations. Averaged across more than a dozen models and centered on Chicago, 1.53″ is the blended tally. 

—We NEED THE RAIN. Going into this rain event, Chicago’s October 2022 rainfall was less than 1/3 normal (0.81″ versus the normal to date of 2.68″. And its fall season precip (since Sept 1) was only roughly half (51%) normal coming in at 3.01″ versus the normal of 5.87″. 

–Regionally and nationally, a majority of areas are running dry at the moment. 82% of the Lower 48 is assessed with sub-par moisture by the DROUGHT MONITOR—59.4% of it in a state of drought. Across Illinois, 76% of the state is drier than normal and 23.8%–including the Chicago area’s southern counties, are in a state of moderate drought—in spots even drier than that. 

—After last week’s wild swing in temps—from a sporadically snowy 43-deg high last Monday to a high of 76 Friday and 79 both Saturday and Sunday. 

–Halloween trick-or-treat weather Sunday, for those areas that have trick-or-treating ahead of Halloween Day itself (Monday, Oct 31)–could include some afternoon or evening showers. The current read on Monday evening is rains will have moved out. 

–This week’s will be more stable with daytime highs holding mainly to the 50s. Easterly winds off Lake Michigan will check any large temp increases despite the return of drier weather as Wednesday proceeds and through the remainder of this work week. Despite the cooler daytime highs, interestingly, this week (the Monday through Saturday period) as a whole will come in 3.5-deg ABOVE NORMAL—and NEXT WEEK LOOKS EVEN WARMER, coming in an eye-catching 8.5-deg above normal.  

—And with next week’s warmth comes better-organized southwest winds which overcome lake cooling and hint at temps even higher than the averaged 60s off a constellation of weather forecast models. 

–Also of interest is the fact we see the Gulf of Mexico opening up and sending a flood of moisture northward again. This could signal a wetter pattern than that which has dominated much of the fall season. 

–BY THE WAY, my WGN meteorological colleague has checked the 151 observational record for Chicago and finds there historical support for additional warm weather before the cold of winter locks in. 88 of the past 151 years have produced at least one additional 70-deg temp beyond Oct 25—and three years have produced as many as eight additional 70s—including 1964, 1971 and 1991. But 80-deg prospects aren’t as impressive. Only 6 to the past 152 years have managed 80-deg highs beyond this point in the year. 

HERE’S MY LATEST CHICAGO METRO FORECAST: 

TONIGHT: Rain and turning windy locally heavy rainfall at times. Some lightning and thunder is NOT out of the question. Wind gusts may top 30 mph at times. Low 44. 

WEDNESDAY: Windy and cooler. Rain ends early, clearing follows. Skies become sunny during the afternoon. 30 mph morning gusts come down slowly. High 54. 

WEDNESDAY NIGHT: Becoming partly cloudy. Cooler. Diminishing winds. Low 39—but low 30s with possible frost inland. 

THURSDAY: More cloudiness, seasonably cool. High 54. 

FRIDAY AND SATURDAY: Mostly sunny—slowly warming days with light easterly winds off Lake Michigan; a clear cool night between. High Friday 56. Low Friday night 40—30s inland. High Saturday 59. 

SUNDAY: Cloudy—growing prospects for afternoon and nighttime showers. High 58. 

MONDAY (HALLOWEEN DAY): Opens clouds with a few possible lingering showers. Partial clearing in the afternoon. High 59.