FIRST, THE TUESDAY WEATHER HEADLINES

–The Chicago area, which has been VERY DRY, is on the way to its biggest rainfall in a month–since 1.47″ fell Sept 11-12.  We need the rain. Only 0.05″ has fallen this month and my WGN meteorological colleague Mark Carroll notes the period from Sept 26 through yesterday October 10–with its paltry 0.05″—is the driest such period in the 42 years since 1980.  IN checking the books, I’ve found 1.72″ is normal for that period–so the past 15 days have all of 3% of the normal rain here in Chicago.

–Modeling suggests waves of showers and thunderstorms tonight through midday Wednesday may produce anywhere from 0.60″ to 1.20″–and in a few spots, locally more. And the prospect thunder is to occur in some of these shower runs at 70 to 80% through between now and daybreak and 50-60% Wednesday through midday. Rains nor thunder will be continuous, but when it rains, there could be downpours.

–Rain chances reach 80% tonight; 70% Wednesday–but rains begin to ebb after early Wed afternoon with a cold frontal passage.

–As mentioned here yesterday, gusty winds are very much a pattern of this pattern over the coming week with model estimates of gusts peaking at 46 mph before Wednesday closes; to 39 mph Thursday; 37 mph Friday;  43 mph Sat; 39 mph Sun and 34 mph Monday.  The gustiest winds occur as low level NW winds marry with a NW flow aloft.

–What follows the current rain–some of it thundery—is some cool weather as steering winds out of northern Canada. A pool of cold air aloft is to destabilize that atmosphere Thursday and Friday promoting a fair amount of cloudiness with peeks of sun.

–A second push of chilly air hits later Sunday into Monday and Tuesday and the current read on that cool surge is that it’s to be cooler than the one due later this week.

–Longer range guidance suggest the chill gives way to an ABOVE NORMAL period in the week following next.

HERE’S THE CHICAGO METRO FORECAST

TONIGHT: Waves of showers and thunderstorms–some capable of downpours. Mild for the season and breezy. Low 53.

WEDNESDAY: More cloudy than not with sporadic showers and some thunderstorms continue through midday–then winding down in the afternoon. Clouds break allowing partial clearing by late in the day. Quite windy. High 63.

WEDNESDAY NIGHT: Less cloudiness, breezy and cooler. Low 45–but near 40 far west and northwest toward the Fox Valley, McHenry county and west. 

THURSDAY: Mixed sun and clouds, windy and noticeably cooler. Chance of a few spotty afternoon showers, mainly north. Gusts above 35 mph likely. High 52.

FRIDAY: Partly cloudy to cloudy at times, blustery and cool. A few isolated afternoon showers. High 52–a reading 12-deg below normal.

SATURDAY: A good deal of cloudiness, continued breezy. Several showers possible. High 57.

SUNDAY: Sunshine at the start–but clouds build, breezy and cool. High 55.

MONDAY: Mixed sun and clouds, windy and cool for the season. Several spotty afternoon showers possible. High 47.

TUESDAY: Partly sunny but cool and still breezy. High 50.