Chicago Weather Forecast (O'Hare Official) 9:18 am CDT Sep 21, 2017 with Forecast Discussion

Today: Mostly sunny, with a high near 92. Heat index values as high as 96. South wind 5 to 10 mph, with gusts as high as 15 mph.

Tonight: Mostly clear, with a low around 71. South wind around 5 mph.

Friday: Sunny, with a high near 91. South southwest wind 5 to 10 mph.

Friday Night: Mostly clear, with a low around 69. South wind around 5 mph.

Saturday: Sunny, with a high near 90. South wind around 5 mph.

Saturday Night: Mostly clear, with a low around 67.

Sunday: Sunny, with a high near 87.

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

Monday: Sunny, with a high near 85.

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

Tuesday: A slight chance of showers. Mostly sunny, with a high near 83.

Tuesday Night: Mostly cloudy, with a low around 61.

Wednesday: A chance of showers and thunderstorms. Partly sunny, with a high near 73.

 Amf Ohare IL  41.98°N 87.9°W

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


630 AM CDT Thu Sep 21 2017


Through tonight...

A few festering showers will continue early this morning near the I-39 corridor ahead of a weakening cold front as it encroaches on an expansive ridge centered along the Appalachians. Overnight satellite imagery shows convection back-building across Iowa with diminishing chances for thunders across the local CWA. Hi-res models are in good agreement on precipitation ending around or shortly after daybreak today.

Meanwhile, an upper low is digging across the Pacific Northwest this morning and will approach the Intermountain West this evening. In response, southwest flow will increase across the Great Plains and Mississippi Valley today lifting a warm front into the far Upper Midwest which should be the focus for convection today. This leaves the local area well entrenched in the warm sector and capped by around +20C 850mb temps. Assuming the broad cirrus shield this morning is able to clear out, this should leave the area under partly cloudy to mostly sunny skies this afternoon which will contribute to another day of temperatures well into the 80s and low 90s. Record high temperatures today are 92F for Chicago and 94F for Rockford, the former having the best chance of being tied or broken today. Dewpoints in the mid to upper 60s today will result in heat indices in the upper 90s to around 100F this afternoon.




Friday through Wednesday...

Large blocking high will be in place over the eastern half of the U.S. Friday through the middle of next week resulting in a stretch of above normal temperatures and primarily dry conditions. Friday and Saturday in particular look very warm with record or near record highs possible. Record highs for September 22nd are 92F for Chicago and 93F for Rockford. Record highs for September 23rd are 91F for Chicago and 92F for Rockford. In addition, dewpoints in the mid to upper 60s these days will make for continued muggy conditions.

Upper ridge axis shifts slightly farther east Monday and Tuesday. Temperatures remain well above normal this time frame, but should be tempered some as the air mass modifies and cloud cover increases from upstream convection. GFS indicates the potential for showers and thunderstorms Monday afternoon due in part to steep low level lapse rates. Not ready to bite off on this though as forcing is minimal and forecast soundings show overall weak instability due to poor mid and upper level lapse rates and some capping from the 700-800mb warm nose. Meanwhile, ECMWF maintains a dry forecast on Monday.

GFS and ECMWF remain in reasonable agreement that the strong upper ridge will begin to breakdown late Tuesday or Wednesday allowing a cold front to sweep across the local area. This looks to be the next decent shot for showers and thunderstorms and temperatures will moderate behind the front closer to seasonal norms.



.AVIATION... For the 12Z TAFs...

Convection continues to dissipate as it encounters more stable air over IL. No additional rain is expected at any of the TAF sites. Looking at southerly winds and VFR conditions through Friday morning. Cloud cover may linger longer than currently forecast, but it will be VFR.




A cold front will move over central Lake Michigan today and then lift north as a warm front tonight. Wind direction will vary on either side of the cold front, but southerly winds follow the warm front. A blocky pattern then sets up and remains in place through early next week. A high pressure ridge will sit over the eastern U.S. while a low pressure trough extending from the northern Mississippi Valley to the southern Plains remains stationary as it weakens. This pattern will produce southerly winds through Tuesday. While guidance differs on how the pattern breaks, the models agree that winds will shift to northwest Wednesday.




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Arlington Heights Weather Forecast
Chicago allergy weather
Chicago arthritis weather
Chicago respiratory weather

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Hazardous Weather Outlook National Weather Service Chicago/Romeoville IL 326 AM CDT Thu Sep 21 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 220830- 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- 326 AM CDT Thu Sep 21 2017 /426 AM EDT Thu Sep 21 2017/


.DAY ONE...Today and Tonight.

WEATHER HAZARDS EXPECTED:   Limited Thunderstorm Risk this morning.   Limited Excessive Heat Risk.


An isolated thunderstorm or two is possible early this morning, generally near the I-39 corridor over north central Illinois. Severe storms are unlikely.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Tuesday and Wednesday...   Limited Thunderstorm Risk.


Spotter activation will not be necessary through tonight.


Moving northeast at 25 MPH.