Scattered Thunderstorms Monday Afternoon

Scattered thunderstorms occurred across the area Monday afternoon and early evening.  The severe weather threat was fairly minimal given the lack of stronger winds aloft, yet, some thunderstorms still became strong and at least one became severe.  In addition, several funnel clouds were reported across northern Illinois.  So what was going on?

The short answer: Boundaries! 

Radar imagery Monday afternoon was filled with several criss-crossing outflow boundaries along with a lake breeze pushing inland from Lake Michigan.  As mentioned, the winds aloft were marginal which inhibited a widespread severe weather threat; however the presence of these boundaries, especially when they intersect at right angles to storms, can locally enhance the shear, especially in the lowest levels of a thunderstorm.  Because of the motions of the thunderstorms and the boundaries, they only momentarily intersected; however, this was enough to cause storms to pulse up in intensity and sometimes produce brief funnel clouds.  If the storms were able to “ride” the boundaries for a longer duration, then the severe weather threat and tornado threat may have been greater.

A thunderstorm over DuPage County briefly pulsed up enough to warrant a severe thunderstorm warning.  A severe microburst occurred near the town of Glen Ellyn producing mainly moderate tree damage across town.

So while the severe weather threat was fairly low today, this serves as an important reminder to have a way to receive severe weather alerts during quickly changing weather conditions.

 Rainfall Amounts

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
1021 AM CDT TUE AUG 11 2015

...MORNING RAINFALL ROUNDUP...

   THE FOLLOWING ARE RAIN AMOUNTS FOR THE PREVIOUS 24-HOURS
   AS MEASURED IN THE MORNING BY NWS COOPERATIVE OBSERVERS
   AND COCORAHS OBSERVERS.
   OBSERVATIONS ARE USUALLY TAKEN BETWEEN 6 AND 8 AM.

   24-HOUR RAINFALL AMOUNTS
       FOR TUESDAY(08/11/15)...


ILLINOIS                                       RAIN
  LOCATION (COUNTY):                           FALL (IN)

  WINTHROP HARBOR 1SSW (LAKE)..................1.62
  ALGONQUIN 1N (MCHENRY).......................1.58
  WINTHROP HARBOR (LAKE).......................1.54
  MALTA (DE KALB)..............................1.40
  WAUKEGAN 2N (LAKE)...........................1.20
  BEACH PARK 1W (LAKE).........................1.14
  STEWARD (LEE)................................1.13
  HOFFMAN ESTATES 5W (COOK)....................1.12
  DOWNERS GROVE 0.4NNE (DU PAGE)...............1.03
  MUNDELEIN (LAKE).............................1.02
  ROCHELLE (OGLE)..............................1.01
  PARK FOREST (COOK)...........................0.99
  WAUKEGAN (LAKE)..............................0.99
  BARRINGTON (LAKE)............................0.95
  LILY LAKE 2E (KANE)..........................0.94
  GURNEE 2NE (LAKE)............................0.91
  ELGIN (KANE).................................0.90
  DOWNERS GROVE 1S (DU PAGE)...................0.86
  HAMPSHIRE (KANE).............................0.84
  COAL CITY 4NNW (GRUNDY)......................0.83
  CARBON HILL 3.1N (GRUNDY)....................0.83
  AURORA (KANE)................................0.82
  MUNDELEIN 2WNW (LAKE)........................0.82
  PARK FOREST 1SW (COOK).......................0.81
  YORKVILLE 2SE (KENDALL)......................0.81
  PAW PAW (LEE)................................0.77
  GLEN ELLYN 1NNW (DU PAGE)....................0.74
  SUGAR GROVE 1ENE (KANE)......................0.73
  ASHTON (LEE).................................0.73
  CARY (MCHENRY)...............................0.72
  MUNDELEIN (LAKE).............................0.67
  ROCHELLE (OGLE)..............................0.65
  DE KALB (DE KALB)............................0.64
  SUGAR GROVE 1NE (KANE).......................0.64
  LAKE VILLA 1SSW (LAKE).......................0.63
  BATAVIA 1WNW (KANE)..........................0.61
  MORRIS (GRUNDY)..............................0.60
  OAK PARK 2S (COOK)...........................0.58
  LAKE ZURICH (LAKE)...........................0.54
  SCHAUMBURG 3WSW (COOK).......................0.53
  COAL CITY 3N (GRUNDY)........................0.52
  BUFFALO GROVE 2N (LAKE)......................0.52
  MENDOTA 2SE (LA SALLE).......................0.52
  WESTMONT (DU PAGE)...........................0.52
  ORLAND HILLS 1SE (COOK)......................0.51
  ELBURN (KANE)................................0.50
  GLEN ELLYN 1NE (DU PAGE).....................0.49
  ELBURN (KANE)................................0.49
  LAKEMOOR 2SE (LAKE)..........................0.49
  AMBOY (LEE)..................................0.48
  LAKE VILLA 2WSW (LAKE).......................0.48
  BATAVIA 1WSW (KANE)..........................0.47
  BATAVIA 2WNW (KANE)..........................0.45
  BRACEVILLE (GRUNDY)..........................0.44
  MONTGOMERY 2SSE (KENDALL)....................0.44
  BATAVIA (KANE)...............................0.43
  ALSIP (COOK).................................0.43
  CHICAGO RIDGE (COOK).........................0.42
  MONTGOMERY 1SSE (KENDALL)....................0.42
  PLANO (KENDALL)..............................0.42
  LAKEMOOR 2NW (MCHENRY).......................0.42
  MIDWAY COOP (COOK)...........................0.42
  OAK PARK 1NNE (COOK).........................0.41
  GENEVA 1SSW (KANE)...........................0.41
  GURNEE 2W (LAKE).............................0.41
  MINOOKA (GRUNDY).............................0.40
  LINCOLNSHIRE 1.3WSW (LAKE)...................0.40
  GENOA (DE KALB)..............................0.39
  ST. CHARLES 6NW (KANE).......................0.39
  EARLVILLE 8SSE (LA SALLE)....................0.39
  LISLE MORTON ARB (DU PAGE)...................0.39
  MAZON 0.5ENE (GRUNDY)........................0.38
  CHANNAHON 2SSE (WILL)........................0.38
  OAK LAWN 2WNW (COOK).........................0.37
  GENEVA 2WSW (KANE)...........................0.37
  DIXON 3NNW (LEE).............................0.35
  ROSELLE 1ESE (DU PAGE).......................0.34
  EARLVILLE 3S (LA SALLE)......................0.33
  DE KALB 2NNE (DE KALB).......................0.33
  BURR RIDGE 2SW (DU PAGE).....................0.33
  OAK LAWN (COOK)..............................0.32
  HIGHWOOD 1S (LAKE)...........................0.32
  WORTH (COOK).................................0.31
  DWIGHT (LIVINGSTON)..........................0.30
  GILBERTS (KANE)..............................0.30
  RIVERWOODS (LAKE)............................0.30
  FOX LAKE 2SE (LAKE)..........................0.30
  OTTAWA (LA SALLE)............................0.30
  SHERIDAN 3SSE (LA SALLE).....................0.29
  BEECHER 3SSE (WILL)..........................0.29
  MENDOTA (LA SALLE)...........................0.28
  SOUTH WILMINGTON (GRUNDY)....................0.27
  NORTH AURORA 2NE (KANE)......................0.27
  BOTANIC GARDENS (COOK).......................0.26
  OTTAWA 2N (LA SALLE).........................0.26
  AURORA (KANE)................................0.25
  ELK GROVE VILLAGE 2WSW (COOK)................0.25
  PLAINFIELD 5SW (KENDALL).....................0.25
  WILMINGTON 6NW (WILL)........................0.25
  MIDWAY (COOK)................................0.25
  ELMHURST (DU PAGE)...........................0.24
  GENEVA 4WSW (KANE)...........................0.24
  BYRON 3N (OGLE)..............................0.24
  ELGIN (KANE).................................0.23
  ELGIN 1S (KANE)..............................0.23
  CHANNAHON 1NNE (WILL)........................0.23
  MACHESNEY PARK 3ENE (WINNEBAGO)..............0.23
  MOUNT PROSPECT 3NE (COOK)....................0.22
  GLENCOE (COOK)...............................0.22
  MORRIS 2SSE (GRUNDY).........................0.22
  WHEELING (COOK)..............................0.21
  CHICAGO 5NE (COOK)...........................0.20
  OTTAWA 1NW (LA SALLE)........................0.20
  CRETE 3E (WILL)..............................0.20
  ROCKFORD 3NE (WINNEBAGO).....................0.20
  JOLIET (WILL)................................0.19
  WILLOW SPRINGS (COOK)........................0.19
  MONEE (WILL).................................0.18
  ROCKFORD (WINNEBAGO).........................0.18
  BONFIELD 4WSW (KANKAKEE).....................0.17
  LOCKPORT 1SE (WILL)..........................0.17
  AURORA 4SE (DU PAGE).........................0.16
  NEW LENOX 3ENE (WILL)........................0.16
  PLAINFIELD 1SW (WILL)........................0.15
  ROMEOVILLE (WILL)............................0.15
  PLAINFIELD (WILL)............................0.15
  LA GRANGE PARK 1SSW (COOK)...................0.14
  BOLINGBROOK 3NE (DU PAGE)....................0.14
  AURORA 4SE (DU PAGE).........................0.14
  NEW LENOX 2SE (WILL).........................0.14
  MANHATTAN 2SE (WILL).........................0.14
  WINFIELD (DU PAGE)...........................0.14
  WEST CHICAGO (DU PAGE).......................0.13
  NAPERVILLE 4SSW (WILL).......................0.13
  NEW LENOX 3E (WILL)..........................0.13
  LANSING (COOK)...............................0.13
  OSWEGO 5SSE (KENDALL)........................0.12
  PALATINE 1E (COOK)...........................0.11
  DWIGHT 4NNW (GRUNDY).........................0.11
  JOLIET 2N (WILL).............................0.11
  WOODSTOCK (MCHENRY)..........................0.11
  BOURBONNAIS (KANKAKEE).......................0.10
  SCHAUMBURG  2E (COOK)........................0.10
  PARK RIDGE 1WNW (COOK).......................0.10
  ELGIN 2WNW (KANE)............................0.10
  PLAINFIELD 2SSE (WILL).......................0.10
  NEW LENOX 4SE (WILL).........................0.10
  JOLIET LOCK/DAM (WILL).......................0.10
  ARLINGTON HEIGHTS 1SW (COOK).................0.09
  LINCOLNWOOD 2E (COOK)........................0.09
  ELMHURST 1ESE (DU PAGE)......................0.09
  STREATOR 1WSW (LA SALLE).....................0.09
  JOLIET 3WNW (WILL)...........................0.09
  HOMER GLEN 1ENE (WILL).......................0.09
  ROSCOE 2ESE (WINNEBAGO)......................0.09
  ROSCOE 2SE (WINNEBAGO).......................0.09
  ELMHURST 2SE (DU PAGE).......................0.08
  GENEVA 2ENE (KANE)...........................0.08
  STREATOR 4ENE (LA SALLE).....................0.08
  PLAINFIELD 3SE (WILL)........................0.08
  MANHATTAN 5ENE (WILL)........................0.08
  MANHATTAN (WILL).............................0.08
  BOURBONNAIS 2NNE (KANKAKEE)..................0.07
  PEOTONE (WILL)...............................0.07
  ELK GROVE VILLAGE 1ESE (COOK)................0.06
  JOLIET (WILL)................................0.06
  MARSEILLES (LA SALLE)........................0.06
  HARWOOD HEIGHTS 2NNE (COOK)..................0.05
  BULL VALLEY 2WNW (MCHENRY)...................0.05
  STREATOR (LIVINGSTON)........................0.05
  NAPERVILLE 2ESE (DU PAGE)....................0.04
  MCHENRY (MCHENRY)............................0.04
  WOODSTOCK 5NW (MCHENRY)......................0.04
  PARK RIDGE (COOK)............................0.03
  KANKAKEE 3SE (KANKAKEE)......................0.03
  LANSING (COOK)...............................0.02
  CAPRON (BOONE)...............................0.02
  CHICAGO 6ESE (COOK)..........................0.02
  ASHKUM 5.6E (IROQUOIS).......................0.02
  DIXON 2SW (LEE)..............................0.02
  KANKAKEE (KANKAKEE)..........................0.02
  OHARE (COOK).................................0.02
  KANKAKEE (KANKAKEE)..........................0.01
  LA SALLE (LA SALLE)..........................0.01
  HEBRON (MCHENRY)............................TRACE
  PONTIAC 1SE (LIVINGSTON)....................TRACE
  ST ANNE (KANKAKEE)..........................TRACE

INDIANA                                        RAIN
  LOCATION (COUNTY):                           FALL (IN)

  WHEATFIELD 3S (JASPER).......................0.40
  RENSSELAER 2SSW (JASPER).....................0.11
  RENSSELAER 5NW (JASPER)......................0.09
  RENSSELAER (JASPER)..........................0.08
  RENSSELAER 2N (JASPER).......................0.05
  DE MOTTE 1NNW (JASPER).......................0.04
  LOWELL 3N (LAKE).............................0.04
  MOUNT AYR 2NNE (NEWTON)......................0.04
  CROWN POINT 2WSW (LAKE)......................0.03
  (W9MAL)MERRILLVILLE 2NNW (LAKE)..............0.03
  VALPARAISO 4SW (PORTER)......................0.03
  CROWN POINT (LAKE)...........................0.02
  RENSSELAER 6SE (JASPER)......................0.02
  DE MOTTE 4SW (JASPER)........................0.02
  VALPARAISO 6SSW (PORTER).....................0.02
  VALPARAISO 7WSW (PORTER).....................0.02
  VALPARAISO 2NW (PORTER)......................0.02
  VALPARAISO 6WSW (PORTER).....................0.02
  INDIANA DUNES (PORTER).......................0.01
  (WV90)HOBART 1ENE (LAKE).....................0.01
  VALPARAISO 1NE (PORTER)......................0.01
  HEBRON 4NE (PORTER)..........................0.01
  RENSSELAER 10NNE (JASPER)...................TRACE
  CROWN POINT 1N (LAKE).......................TRACE
  VALPARAISO 1SE (PORTER).....................TRACE
  PORTAGE 1ESE (PORTER).......................TRACE
  VALPARAISO 5WSW (PORTER)....................TRACE
  MOROCCO (NEWTON)............................TRACE
  VALPARAISO (PORTER).........................TRACE