Flash Flooding and Hail in Illinois, July 22, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
217 PM CDT MON JUL 22 2002

PLENTY OF CONCERNS WITH FOCUS ON SEVERE CONVECTION INTO TONIGHT AND
PRECIPITATION AND TEMPS BEYOND FIRST 24 HOURS.

LATEST 17Z SURFACE ANALYSIS PLACES MAIN SURFACE LOW PRESSURE ACROSS
SOUTHERN CANADA WITH A SURFACE COLD FRONT ACROSS GREAT LAKES REGION
SOUTHWEST INTO THE CENTRAL PLAINS STATES. LATEST 1815Z IR SATELLITE
IMAGE PLACES PLENTY OF CLOUDS ACROSS MICHIGAN SOUTHWEST ACROSS MID
MISSISSIPPI VALLEY. LATEST 1815Z W/V IMAGE PLACES S/W ACROSS CENTRAL
PLAINS STATES/SOUTHWEST IOWA/NORTHWEST MISSOURI. OTHER SW/S WERE
ACROSS WESTERN U.S. NEAR THE COAST.  LATEST 1839Z KILX RADAR
INDICATES SCATTERED THUNDERSTORMS ALONG THE COLD FRONT NORTH OF
PEORIA.  LATEST 1838Z KDVN RADAR INDICATES OTHER SHOWERS AND
THUNDERSTORMS ACROSS CENTRAL AND EASTERN IOWA. LATEST 18Z MSAS AND
LAPS DATA INDICATES CAPES NEAR 4000 J/KG AND LI/S AT -9 ALONG THE
COLD FRONT.

MODELS FAIRLY SIMILAR WITH SOME DIFFERENCES NOTED ELECTING TO USE A
BLEND OF THE MODELS.  PREFER SLOWER MOVEMENT OF COLD FRONT WHICH WAS
DEPICTED BY THE MESOETA.

MODELS HAVE H50 RIDGE MOVING SOUTH AND BUILDING WEST WITH A H50
TROUGH ACROSS GREAT LAKES REGION SOUTH INTO MID MISSISSIPPI VALLEY
BY 06Z TUE.  THIS H50 TROUGH SHIFTS EAST ACROSS EAST COAST BY 00Z
WED.  MODELS DIFFER SLIGHTLY ON TIMING OF COLD FRONT AND PREFER THE
SLOWER MOVEMENT OF COLD FRONT. COLD FRONT IS EXPECTED TO DISSECT THE
CWA BY 00Z TUE...AND REMAIN ACROSS SE ILLINOIS BY 12Z TUE.  COLD
FRONT MOVES SOUTH AS SURFACE HIGH PRESSURE BUILDS ACROSS UPPER
MIDWEST AND GREAT LAKES REGION BY 00Z WED. SURFACE HIGH PRESSURE
MOVES EAST ACROSS EASTERN GREAT LAKES/NORTHEAST U.S. AND A SURFACE
LOW PRESSURE DEVELOPS ACROSS THE PLAINS STATES BY 00Z THU. THIS
SURFACE LOW PRESSURE WAS DEPICTED STRONGER BY THE ETA VERSUS THE AVN
MODEL AND ETA WAS PREFERRED.

850MB TEMPERATURES DROP TO +16C TO +18C ACROSS CWA BY 12Z TUE
THROUGH 12Z WED...THEN SLIGHTLY INCREASES TO +17C TO +19C ACROSS CWA
BY 00Z THU.  THE ETA 310K ISENTROPIC SURFACE INDICATES SOME COND
PRES DEF AND ISENTROPIC LIFT ACROSS CWA THROUGH 06Z TUE...AND
MAINTAINS DECENT COND PRES DEF ACROSS SOUTHEAST ILLINOIS THROUGH 18Z
TUE.  T/H CROSS SECTIONS PROVIDE HIGH RELATIVE HUMIDITY AT LOWER
LEVELS MAINLY THROUGH 00Z WED.  LATEST MODEL SOUNDINGS INDICATE GOOD
INSTABILITY...PW/S AROUND 2.0 INCHES THROUGH 06Z TUE. THEN MAINTAINS
DECENT MOISTURE AT 850MB THROUGH 00Z WED. WILL MENTION A CHANCE FOR
SEVERE AND LOCALLY HEAVY RAINFALL IN FIRST PERIOD ZONES. CURRENT
HEAT ADVISORY WILL BE ALLOWED TO BE EXPIRED.

EXTENDED...LOOKS ON TRACK AND WILL ADD CHANCE OF THUNDERSTORMS ON
MONDAY.

TEMPERATURES FAIRLY SIMILAR AND WILL NOT STRAY FAR FROM GUIDANCE.

...PRELIMINARY CCF FOR COORDINATION PURPOSES...

SPI BB 067/082 059/083 060 13620
PIA BB 065/082 058/082 058 13320
DEC BB 068/082 059/083 060 13630
CMI BB 067/081 057/081 058 13630
MTO BB 070/082 059/083 060 13640
LWV BB 072/083 061/084 062 13762

.ILX...NONE.

BARBUSH/EH