Chicago Weather Forecast (O'Hare Official) 8:16 pm CDT Sep 26, 2017 with Forecast Discussion

Tonight: A 20 percent chance of showers before 2am. Mostly cloudy, with a low around 60. Northwest wind around 10 mph, with gusts as high as 15 mph.

Wednesday: Mostly cloudy, then gradually becoming sunny, with a high near 72. North northwest wind 10 to 15 mph, with gusts as high as 20 mph.

Wednesday Night: Mostly clear, with a low around 51. North northwest wind 5 to 10 mph, with gusts as high as 15 mph.

Thursday: Sunny, with a high near 71. North northwest wind around 5 mph.

Thursday Night: Partly cloudy, with a low around 54. West wind around 5 mph.

Friday: Mostly sunny, with a high near 68.

Friday Night: Mostly clear, with a low around 49.

Saturday: Sunny, with a high near 67.

Saturday Night: Mostly clear, with a low around 49.

Sunday: Sunny, with a high near 70.

Sunday Night: Partly cloudy, with a low around 54.

Monday: Mostly sunny, with a high near 77.

Monday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 59.

Tuesday: A slight chance of showers. Mostly sunny, with a high near 78.

Amf Ohare IL
 41.98°N 87.9°W

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


650 PM CDT Tue Sep 26 2017


Through Wednesday...

One last hurrah with the current late season heat event is ongoing this afternoon, but we are about to take the leap back into fall. ORD did hit break the record high earlier today, now for the seventh day in a row. Showers have developed across north central Illinois ahead of a cold front currently in northwest Illinois. The main upper forcing will pass off to our northwest, and thus deeper saturation for more widespread activity is limited. This should act to keep showers more in the isolated to scattered regime. There is a narrow instability axis ahead of the front, thus an isolated storm is possible, though with the cu field filling in, capping will set in farther downstream.

The weather pattern change will be noticed here through the afternoon and evening as the front moves in. There is a healthy stratus field back behind the cold front, and we will have some of these clouds plus a healthy mid level cloud deck also. Expect somewhat breezy northwest winds, though most upstream sites have topped only out around 20 mph or so. Additional shortwave energy will propagate northwest along the frontal zone keeping some chances for showers into the evening, though coverage will be fairly low.

Wednesday will feel much different across the area in spite of the fact that temperatures will be peak around seasonal normals. After some morning clouds, expect a dry day with partly cloudy skies.




Wednesday night through Tuesday...

Cooler, more seasonal, weather is expected later this week and into this weekend. However, the chances for precipitation through much of the period looks to remain low.

After a pleasant day on Thursday, a mid-level trough is expected to dig southeastward across the Western Great Lakes Region into Friday morning. This feature should push another cold front south over the area Thursday night. Even cooler air in the wake of this front should result in temperatures on Friday only in the 60s across much of northeastern Illinois, and into the low 70s inland. Lake effect showers are likely to largely remain east of the area, though some of these showers and clouds could impact far eastern portions of the area in northwestern Indiana into Friday morning. Otherwise, expect a surface high to build over the Great Lakes late Friday and into Saturday, resulting in continued dry and seasonal weather.

Later in the weekend, the surface high should shift towards New England, and as it does so, the low-level flow should turn southerly again. This should allow for a warming trend and a return to above average temperatures into early next week. The only chance for rain during the period looks to be late Monday through Monday night as a frontal system looks to move across the area. Otherwise, forecast guidance is insistent in rebuilding the upper ridge across the central portion of the country by the middle of next week. This may result in yet another period of well above normal temperatures for the later half of next week.



.AVIATION... For the 00Z TAFs...

A cold front is sweeping across the area this evening. A few showers in northeast Illinois are passing safely north of ORD and there is no sign of concentrated development farther south so have removed VCSH mention. Behind the front, winds are shifting to west-northwest to northwest. There may be a brief period of gustiness with the wind shift at MDW and GYY that will quickly subside based on observations from DPA and ORD. A pocket of MVFR CIGs back to the west could try to work eastward tonight, but confidence is low in prevailing MVFR so have carried SCT030 in the TAFs. On Wednesday, northwest to north-northwest (320-340 degrees) winds are expected with some occasional gustiness in the mid to high teens. The potential exists for winds to turn closer to due northerly with lake influence late in the day at ORD, MDW and GYY but confidence is low. Conditions will be VFR Wednesday and Wednesday evening.




A cold front will push across the lake this evening. In its wake, expect winds to increase up around 25 KT out of the northwest overnight into Wednesday. The winds will gradually ease into Thursday and back more west-southwesterly for a period late Thursday. However, another cold front is expected to drop down the lake Thursday night, with a return to northerly winds up around 30 KT into Friday. Given the amount of cool air expected to shift over the warm lake, waterspouts will also be possible in association with lake effect showers Thursday night into at least Friday morning. A surface high is then forecast to shift over the lake on Saturday.



.LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...Beach Hazards Statement...INZ001-INZ002...5 AM Wednesday to 10      PM Wednesday.

LM...Small Craft Advisory...LMZ744-LMZ745...5 AM Wednesday to 10 PM      Wednesday.

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Hazardous Weather Outlook National Weather Service Chicago/Romeoville IL 314 PM CDT Tue Sep 26 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 272015- 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- 314 PM CDT Tue Sep 26 2017 /414 PM EDT Tue Sep 26 2017/


.DAY ONE...Tonight.

WEATHER HAZARDS EXPECTED:   Limited Thunderstorm Risk.


There is a slight chance of thunderstorms across mainly north central Illinois through early this evening. The risk of any severe weather is low.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Friday...   High Swim Risk. Monday...   Limited Thunderstorm Risk.


Spotter activation will not be necessary through tonight.


Moving to the northeast at 35 mph.