Chicagoan say NO signficant sunshine today. It’s been a damp Wednesday marking the 7th consecutive day to log an ABOVE NORMAL TEMP (thanks to all the moisture today holding overnight temps up) and the 8th straight day of easterly wind in Chicago, which has whipped up waves on Lake Michigan.
The persistence of the late season “warmth” and of the easterly winds is LIVING PROOF our showery upper air low pressure and a sprawling early autumn Canadian high pressure to the north are “hung up” in an UPPER ATMOSPHERIC BLOCKING PATTERN. Blocking patterns slow weather system progression thus producing “extended stays” for weather. You essentially get “trapped” in the weather which is in place when the blocking pattern develops for a extended period of time
Rainfalls with the current sporadically rainy have been ALL OVER THE MAP in terms of totals—with as much as 1.96″ have fallen the past 2 days in Lake Geneva and 1.66″ at Pell Lake—both in southern Wisconsin—plus 1.30″ in Poplar Grove and 1.19″ at Spring Grove in Boone and McHenry counties respectively to as little at 0.02″ at St. Charles, 0.11″ in Roselawn IN and just 0.12″ in Bonfield. (NOTE THAT RAINFALLS CAN VARY WIDELY—EVEN OVER AREAS A LIMITED AS A SINGLE TOWN—so if you’ve seen different amounts in any of the communications, that’s not surprising given the convective nature of the rains).
Totals at O’Hare and Midway thus far have come in at6 0.38″ and 0.25″ respectively.
We’re not done with the rain yet. Additional showers and even a few t-storms are expected and model estimates on rainfall amounts continued widely varied, ranging from as little a 0.10″ to as much as 0.60″ before the rains thin out to several less numerous showers Thursday—and likely ending from Thursday night forward well into next week.
A fair amount of cloudiness is to linger into Thursday, though cloud breaks should allow mixed sunshine. Guidance suggests 80% to 100% cloud coverage as Thursday gets underway. But blend of model cloud coverage forecasts has the percent of the sky with clouds dropping off to 30 to 40% by later in the day . And far sunnier weather is to take up residence this weekend and well into next week. Rain may NOT RETURN to the area until Wed night or Thursday next week!
AND AN EXTENDED RUN OF LATE SEASON WARMTH IS TO DEVELOP AND HANG TOUGH THIS WEEKEND AS OCTOBER ARRIVES (SUNDAY) THROUGH NEXT WEEK. IN fact, modeling continues to indicate each of the coming 14 days will continue above normal—with this weekend hosting afternoon 80s at a time of the year when 70-deg is “normal”.
Chicago’s average daytime temps from Saturday through Thursday of next week are to average 10 to 16-deg above normal. Daytime readings likely won’t break any records—but they’ll not be more than 5 or 10-deg from record levels. Lake breezes will ease so what we are talking about is LATE SEASON BEACH WEATHER—with water temps in Lake Michigan still in the mid 60s.
September, 2023 has moved into its closing 4 days (Believe or not, October, 2023 gets underway THIS SUNDAY!!)
It’s been a month which is running a degree above normal and 0.7-deg warmer than the opening 27 days of Sept a year ago. But moisture has been plentiful. September has temps running among the warmest 18% and rainfalls among the 30% wettest of all 153 Septembers on the books dating back to 1871.
HERE’S MY LATEST THURSDAY CHICAGO METRO FORECAST (9/27/2023):
TONIGHT: Predominately cloudy, damp but mild for the season with steady east winds and sporadic showers—several of them possibly thundery. Low 64.
THURSDAY: A good deal of cloudiness—but breaks will allow some passing sun. Milder than typical in late Sept but with a few left-over showers or sprinkles possible—though not widespread at any given moment. High 72—but 60s lakeshore.
THURSDAY NIGHT: Partly cloudy to cloudy. Low 63.
FRIDAY: Becoming partly sunny and modestly warmer. High 77—closer to 70 lakeshore and beaches.
SATURDAY THROUGH THE WEEKEND AND CONTINUING TILL TUESDAY: Generous daytime sunshine and warmer—only a few mixed clouds. And a few scattered clouds at night. Afternoon temps warm to unseasonably mild levels for so late in the season—and nights remain mild for early October. High Saturday 82; Sunday’s high 84; high Monday 85 and Tuesday’s high 84. Lows 66 Saturday night; 64 Sunday night; 65 Monday night and 65 Tuesday night.
WEDNESDAY: Partly sunny, and warm. High 82.