SEVERE WEATHER UPDATES

The Storm Prediction Center in Norman, Oklahoma is monitoring conditions across northern Illinois for possible severe thunderstorm development as a cold front approaches from Iowa. The peg the probability of the issuance of a watch at 40 percent.

  AREAS AFFECTED...NRN IL...SRN WI

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 052102Z - 052230Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...A CONDITIONAL THREAT OF SUPERCELLS WITH LARGE HAIL AND
   DAMAGING WINDS EXISTS ACROSS FAR NRN IL AND SRN WI...AND THE AREA IS
   BEING MONITORED FOR POSSIBLE DEVELOPMENT.

   DISCUSSION...THE AIR MASS ACROSS THE REGION WAS AFFECTED BY EARLY
   DAY CONVECTION...BUT SOME RECOVERY HAS TAKEN PLACE. STREAMLINES ARE
   CONVERGING OVER THE AREA BUT SOME CAPPING EXISTS. THE SURFACE
   THETA-E AXIS REMAINS W OF THE AREA...BUT MORE BUOYANT AIR MAY
   EVENTUALLY MOVE IN SLOWLY FROM THE SW. IT IS UNCLEAR IF THE FORCING
   WILL OVERCOME CAPPING...BUT IF IT DOES...CONDITIONS WILL BE QUITE
   FAVORABLE FOR HAIL AND WIND.

The Storm Prediction Center in Norman, Oklahoma continue to keep Illinois and the Chicago Metro area along with the rest of the eastern and southern Midwest in a slight risk area for severe storm development. A cold front currently lying from the Door Peninsula in Wisconsin southwest through eastern Iowa to northwest Missouri. The air ahead of the front is moist and unstable with dew points in the middle and upper 60s and with afternoon heating peaking, thunderstorms could develop rapidly as the cold front presses east.

SPC Day 1 Severe Weather Outlook

The National Weather Service has issued a Severe Thunderstorm Watch for Chicago as well as many northern and western suburbs until 2AM Wednesday.

A line of severe thunderstorms has been raking across southern Wisconsin this evening, and is starting to drop south toward northern Illinois.  The main threat from this line of storms will be damaging winds.  Frequent lightning as well as torrential downpours are also expected.  The storms and associated winds will begin to impact Chicago's northern suburbs between 9:30PM and 11PM.

Below:  Counties included in Severe Thunderstorm Watch 616 until 2AM are shaded in pink.

An 8PM update from the Storm Prediction Center includes much of the Chicago area in it's severe weather outlook for tonight.

A line of severe thunderstorms has been raking across Wisconsin this afternoon and evening, and is moving southeast toward Chicago and northeast Illinois.

BELOW:  Severe weather risk overnight in the areas shaded in yellow.

All Chicago area Flash Flood Warnings have been allowed to expire as the heaviest rain has shifted south and east of the area.  Most of the roads and viaducts that were closed due to flooding from excessive rainfall have re-opened.

While flooding eases, dense fog is rapidly forming over some of Chicago's western suburbs.  A Dense Fog Advisory is in effect for most of the metro area until 8AM Monday morning.

UPDATE 9:01PM:  Rainfall totals at several Chicago area locations are approaching four inches.

Showers and thunderstorms producing excessive rainfall are expected to shift south of the City of Chicago by 11PM. For the remainder of the evening, the heaviest rainfall (1" to 2") will occur over Chicago's southern suburbs as well as northwest Indiana.

Here are a few of latest rainfall reports:

3.67"  Chicago- North Ave at Clark
3.64"  Oak Park
3.50"  Aurora
3.44"  Chicago- Ashland at Jackson
3.16"  Lisle
3.05"  Oak Brook
2.98"  Chicago- North Ave at Halsted
2.94"  Chicago- Midway Airport
0.53"  Chicago- O'Hare Airport
0.41"  Wheeling
0.17"  Waukegan

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7:40PM: Slow moving showers and thunderstorms have dropped over three inches of rain across portions of the Chicago area.  The City of Chicago as well as the western suburbs have been hardest hit by the heavy rain.

Flooding closed all southbound lanes lanes of Lake Shore Drive shortly after 7PM.

Pockets of locally heavy rain are expected to continue through Midnight.

Here are a few of the latest rainfall totals:

3.21"  Chicago- North Ave at Clark
2.63"  North Aurora
2.58"  Chicago- North Ave at Halsted

The National Weather Service has issued a Flash Flood Warning for central Cook County until 1:30AM Monday. Details on the warning can be found here.

A Flash Flood Warning has been issued for some of Chicago's western suburbs In Du Page, Kendall, Will and Kane counties until 2:00AM Monday.  Details on the warning can be found here.

UPDATE 2:50PM:  A thunderstorm that prompted a warning for NW Cook county is located near Schamburg at 2:50PM.  This cell is still producing small, non-severe hail as it slowly drifts south at 5 to 10 mph.

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