Chicago Weather Forecast (O'Hare Official) 12:58 pm CDT Sep 18, 2017 with Forecast Discussion

This Afternoon: Sunny, with a high near 76. East northeast wind 5 to 10 mph.

Tonight: A slight chance of showers between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 63. East wind around 5 mph. Chance of precipitation is 40%.

Tuesday: A chance of showers and thunderstorms before 1pm, then a slight chance of showers. Partly sunny, with a high near 80. Calm wind becoming east around 5 mph in the morning. Chance of precipitation is 30%.

Tuesday Night: Partly cloudy, with a low around 66. Southeast wind around 5 mph.

Wednesday: Mostly sunny, with a high near 87. South wind 5 to 10 mph.

Wednesday Night: A 30 percent chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 67.

Thursday: A 20 percent chance of showers and thunderstorms before 1pm. Mostly sunny, with a high near 85.

Thursday Night: Partly cloudy, with a low around 67.

Friday: Sunny, with a high near 86.

Friday Night: Mostly clear, with a low around 65.

Saturday: Sunny, with a high near 84.

Saturday Night: Mostly clear, with a low around 63.

Sunday: Mostly sunny, with a high near 82.

 Amf Ohare IL  41.98°N 87.9°W

Area Forecast Discussion below ad ...

National Weather Service Chicago/Romeoville, IL
GO Current Forecast Discussion


1228 PM CDT Mon Sep 18 2017


Through tonight...

High pressure will build across the western Great Lakes today while the cold front that passed over the region yesterday settles over the Ohio Valley. East to northeast flow will hel Ptemper afternoon highs today, especially near Lake Michigan where onshore flow will keep temperatures only in the low 70s. Farther inland expect afternoon highs in the mid to upper 70s.

Meanwhile, a shortwave trough lifting across the central Great Plains this morning will lift across the mid Mississippi Valley this evening, crossing the river around 00Z. Expect increasing cloud cover out ahead of the wave late this afternoon and evening, and there is a chance for showers and thunderstorms this evening and tonight. Have backed off on PoPs before 00Z given the later forcing and initially dry low/mid levels that will be hard to overcome by the weak forcing. Also lowered PoPs some the evening and overnight, especially north of the I-88 corridor, given the less favorable diurnal timing. Much better chances will be well to our west on the nose of the low level jet over the mid Missouri Valley overnight.




Tuesday through Sunday...

Expect a warm pattern throughout much of the extended time frame as an increasingly amplified ridge takes hold over the Great Lakes and eastern CONUS. There could be a few lingering showers with the shortwave trough that starts to move across the area tonight primarily early in the day Tuesday with dry conditions favored in the afternoon. Otherwise not much going on Tuesday which will likely be the last near normal day temperature-wise before a big warmup takes hold Wednesday. A strong jet digging into the Pacific NW through the early part of the week will carve out a deep trough over the West while downstream amplification of the ridge is expected over the Upper Midwest. Very warm 850mb temps to around 20C will be transported all the way into the Dakotas Tuesday and the thermal ridge will inch east over the local area by Wednesday resulting in well above normal temperatures. Afternoon highs Wednesday are expected to be into the upper 80s with some locations tagging 90.

Thursday through the weekend, strong upper ridge becomes increasingly blocky which should lock the area into a continued warm pattern. Guidance suggests a cold front coming up against the ridge Wednesday night into early Thursday could bring a decaying line of showers and thunderstorms to or at least close to the local area, but beyond that it appears the strong ridge will keep any precipitation off to our west with primarily dry conditions locally.



.AVIATION... For the 18Z TAFs...

Quiet weather is expected across the area for the rest of today, with only some high level clouds shifting over the region. Otherwise, expect the winds to remain easterly 6 to 9 KT through the afternoon.

The chances for a period of showers, and perhaps an embedded thunderstorm, will increase across the area late this evening as an upper level disturbance approaches the area. The best timing for this activity looks to be from around 06-07Z through around 11Z. Otherwise, expect the possibility for a period of lower CIGs, possibly down into the MVFR range, very late tonight into early Tuesday morning.




High pressure over the upper midwest will dominate the pattern today and shift into southeast Canada tonight.  Northeast winds diminish as the high builds overhead, and then become southeast behind the high.  The high pressure ridge remains over the eastern third of the CONUS while a low forms over the Dakotas Tuesday. The low deepens over Saskatchewan, and south winds increase as the pressure gradient tightens over the lake.  The low`s cold front diminishes just west of the Mississippi River Wednesday, and it looks like southerly winds will persist into the weekend.




+ + + + + +

Important links below ad ...
NWS Forecast Chicago (O'Hare)
(NEXRAD Radar Chicago)
(Chicagoland Weather Radar)
(Satellite Cloud Cover East United States)
(US Weather Forecast Chart)
Ultraviolet Index/UV Index
Chicagoland Sunrise, Sunset and Solar Information for Chicago area
Chicagoland Moonrise, Moonset and Lunar Phase information for Chicago area

Full climate/weather details
(Desktop Mac/PC links)

Chicago record high temperatures

Chicago record low temperatures

Chicago extreme records

Chicago normal temperatures

Chicago Weather Radar

Chicago Weather Forecast

See also ...
Arlington Heights Weather Forecast
Chicago allergy weather
Chicago arthritis weather
Chicago respiratory weather

Much of the information in, Chicago Weather Stations and Chicago Weather Station consists of material from the National Weather Service, which is in the public domain (See ABOUT section).


Hazardous Weather Outlook National Weather Service Chicago/Romeoville IL 320 AM CDT Mon Sep 18 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 190830- Winnebago-Boone-McHenry-Lake Illinois-Ogle-Lee-De Kalb-Kane- DuPage-Cook-La Salle-Kendall-Grundy-Will-Kankakee-Livingston- Iroquois-Ford-Lake Indiana-Porter-Newton-Jasper-Benton- 320 AM CDT Mon Sep 18 2017 /420 AM EDT Mon Sep 18 2017/


.DAY ONE...Today and Tonight.

WEATHER HAZARDS EXPECTED:   Limited Thunderstorm Risk.


A few thunderstorms are possible this evening and tonight. Severe thunderstorms are not expected.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday through Thursday...   Limited Thunderstorm Risk.


Spotter activation will not be necessary through tonight.


Moving east to northeast at 20 MPH.