Tuesday Evening Weather Update: Strong Storms and Heavy Rain

1:15am Update: The heaviest of the thunderstorms have moved to the east of Rockford, but there is still very heavy rain falling through Lee and central/southern DeKalb counties.  The rain will continue for the next couple of hours, but the severe threat has diminished.  Flash Flood Warnings do remain in effect for Jo Daviess and Stephenson counties.

Storm reports from the line of storms that moved through can be found below:
(12:38:23 AM) nwsbot: Local Storm Report by NWS LOT: Rockford Airport [Winnebago Co, IL] asos reports HEAVY RAIN of M1.11 INCH at 12:30 AM CDT -- fell in 36 minutes


(12:24:46 AM) nwsbot: Local Storm Report by NWS LOT: Oregon [Ogle Co, IL] 911 call center reports TSTM WND DMG at 14 Jun, 11:50 AM CDT -- numerous trees and powerlines down throughout the county, too busy to give exact locations, but oregon hit hard.


(12:18:54 AM) nwsbot: Local Storm Report by NWS LOT: Rockford [Winnebago Co, IL] trained spotter reports TSTM WND GST of E55.00 MPH at 12:10 AM CDT -- estimated 55 mph gust with small branches down

(12:18:54 AM) nwsbot: Local Storm Report by NWS LOT: Rochelle [Ogle Co, IL] awos reports TSTM WND GST of M47.00 MPH at 12:15 AM CDT --

(12:31:40 AM) nwsbot: Local Storm Report by NWS LOT: 2 S Winnebago [Winnebago Co, IL] 911 call center reports TSTM WND DMG at 14 Jun, 11:55 AM CDT -- powerlines downed near alworth

(12:02:46 AM) nwsbot: Local Storm Report by NWS DVN: Lena [Stephenson Co, IL] emergency mngr reports FLASH FLOOD at 11:50 PM CDT -- highway 20 near lena reported to have 6 inches of water across it.

(12:45:12 AM) nwsbot: Local Storm Report by NWS MKX: Janesville [Rock Co, WI] 911 call center reports HEAVY RAIN of E2.50 INCH at 12:35 AM CDT -- rock county dispatch reported water covered roads around the county. rainfall total of 1.6 to 2.5 inches is from radar estimate. electrical transformers have blown in scattered locations across the county.

Storms moving in from the west have gained a little more speed and could pose a wind threat for the next couple of hours.  Wind gusts near 50-55mph are possible with this line, along with the heavy rainfall.

Read the technical discussion here from the Storm Prediction Center









11:20pm Update: Strong winds likely between Forreston and Polo with the storm moving into western Ogle County.  Wind gusts 45-55mph possible with this line.







The Severe Thunderstorm Watch has been cancelled for Stephenson, Jo Daviess and Carroll counties.  Main threat continues to be heavy rainfall through 2am.


Flash Flooding Update:

Read the technical discussion from the Weather Prediction Center regarding the flash flooding potential tonight.


SUMMARY...CONVECTION ON THE NOSE OF A LOW LEVEL JET COULD PRODUCE
A SHORT TERM FLASH FLOOD THREAT ACROSS PORTIONS OF SOUTHERN WI AND
NORTHERN IL INTO EARLY MORNING HOURS.

DISCUSSION...CONVECTION CONTINUES TO MOVE ACROSS EASTERN IA INTO
SOUTHERN WI AND NORTHWEST IL...IN RESPONSE SYNOTPIC SCALE ASCENT
AHEAD OF A SHORT APPROACHING FROM THE CENTRAL PLAINS. THE ACTIVITY
APPEARS TO BE TIED TO THE NOSE OF THE LOW LEVEL JET (20 TO 30
KNOTS ACROSS CENTRAL AND NORTHERN IL INTO SOUTHERN WI PER REGIONAL
VWP)...WHERE PRECIPITABLE WATER VALUES HOVER NEAR 1.75 INCHES
(WHICH IS ABOVE THE 99TH PERCENTILE FOR MID JUNE).

THE CONVECTION IS ABOUT TO LEAVE THE EASTERN EDGE OF MPD 350...ON
THE EDGE OF THE BEST INSTABILITY AXIS. THE AIRMASS BECOMES LESS
UNSTABLE ACROSS CENTRAL AND NORTHEAST WI...WHERE THE 00Z KGRB
SOUNDINGS SHOWED LITTLE INSTABILITY. THE BEST THRUST OF
INSTABILITY WILL BE ACROSS EASTERN IA INTO NORTHERN IL...WHERE
MUCAPE VALUES ARE STILL IN THE 500 TO 1000 J/KG RANGE. IN
ADDITION...THE MOISTURE FEED FROM THE SOUTH IS QUITE
IMPRESSIVE...WITH A 2.20 PRECIPITABLE WATER VALUE AT KDVN.

THE SHORT TERM THREAT FOR FLASH FLOODING IS EXPECTED ACROSS
PORTIONS OF FAR EASTERN IA...SOUTHERN WI INTO NORTHERN IL...WHERE
THE COMBINATION OF MOISTURE AND INSTABILITY CAN SUPPORT THE
THREAT. FURTHER NORTHEAST INTO CENTRAL WI... INSTABILITY DOES NOT
APPEAR AS THOUGH IT CAN SUSTAIN AN ORGANIZED FLASH FLOOD THREAT.

THERE IS A SIGNAL IN THE LATEST HRRR/EXPERIMENTAL HRRR/12Z ARW FOR
AN ADDITIONAL 1-2 INCHES ACROSS THESE AREAS...AND MESONET
OBSERVATIONS NEAR AND SOUTH OF THE WARM FRONT HAVE BORNE THIS OUT.
THE ADDITIONAL AMOUNTS COULD SUSTAIN A FLASH FLOOD THREAT INTO THE
EARLY  MORNING HOURS.

9:50pm Update: A Severe Thunderstorm Warning has been issued for Stephenson and Carroll counties until 10:45pm.  This storm was located just to the north of Mount Carroll and moving east/northeast at 35 mph.  Cities likely impacted by this storm include: Freeport, Pearl City, Cedarville, Ridott and German Valley.  Stay indoors and away from windows until this storm passes.

(9:38:06 PM) nwsbot: Local Storm Report by NWS DVN: Galena [Jo Daviess Co, IL] law enforcement reports FLASH FLOOD at 09:36 PM CDT -- flash flooding occurring in town.



9pm Update: A Flash Flood Watch has been issued for Winnebago, Boone, McHenry, Ogle, Lee and DeKalb counties until 6am Wednesday.  Incoming thunderstorms over Wisconsin and Northwest Illinois have had a history of producing very heavy rainfall.  While not widespread tonight, rainfall amounts of 3" to possibly 4" will be possible by Wednesday morning.



8:25pm Update: A Flash Flood Warning has been issued for Jo Daviess County until 2:30am Wednesday.  Radar estimated rainfall amounts of up to 3" of rain has fallen in the warned area.  Another 2" to 3" is possible.  With night approaching, it's important to remember to never drive through a flooded roadway.

6:20pm Update: Shortly before 6pm a Severe Thunderstorm Warning had been issued for Ogle County.  That warning has since been allowed to expire as the storm has fallen below severe limits.  However, it will continue to produce heavy rainfall as it slides into Winnebago County.

Additional thunderstorms have developed just south of our viewing area - with a Tornado Warning for Henry County until 7pm.  This storm is currently moving to the east at 15 mph.

A Severe Thunderstorm Watch has been issued for Jo Daviess, Stephenson and Carroll counties until 11pm Tuesday evening.

A warm front developing southwest of Rockford has a line of mostly non-severe storms forming along it.  At times those storms have shown enough strength to potentially produce a few stronger wind gusts.  However, most of the severe weather has been further northwest over Minnesota and northern Iowa closer tied to an area of low pressure.

A slight decrease in instability over northern Illinois has allowed for a very slow weakening trend in the current band over NW Illinois, but those storms will continue to march to the Northeast.  Greatest threat with these will be heavy rainfall.

Storms further west in Iowa will continue to grow in coverage through the evening and pose another risk for thunderstorms into the evening and overnight.  Again, heavy rainfall is going to be the greatest threat with any storms that do move through.