Flash Flood in Illinois, August 13, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
230 PM CDT TUE AUG 13 2002

FORECAST CONCERNS CONTINUE TO BE MOVMNT OF COLD FRONT ACRS THE
FORECAST AREA OVR THE NEXT 24 TO 36 HOURS AND PLACEMENT OF HEAVIEST
RAINFALL.

18Z SFC ANALYSIS HAS COLD FRONT LOCATED FROM NEAR RFD TO JUST SOUTH
OF GALESBURG TO NORTH OF KIRKSVILLE. BNDRY HAS MOVED VERY LITTLE OVR
THE PAST SVL HOURS AS WEAK WAVES OF LOW PRESSURE MOVE ALONG THE
BNDRY. SATELLITE INDICATING CONVECTIVELY INDUCED VORT ACRS ERN IL
RESPONSIBLE FOR THE STORMS TO OUR NORTH AND EAST WITH ANOTHER VORT
LOBE SEEN ON WATER VAPOR LOOP ACRS CNTRL AND SRN MO. MORE ORGANIZED
CONVECTION ASSOCIATED WITH THIS SHORWAVE WITH PROFILERS INDICATING
40-50 KTS OF FLOW (AT 500 MB) AT THE REAR OF THE COMPLEX. RADAR
MOSAIC SHOWING EXTENSIVE CLUSTER OF STORMS ACRS NRN ARK...SRN MO
AND SRN IL TRACKING ENE. AS FAR AS THE FINER DETAILS...IT LOOKS AS
IF THE ETA HAS DONE THE BETTER JOB OF FRONTAL AND QPF PLACEMENT OVR
THE PAST 24 HRS SO WL TEND TO LEAN IN ITS DIRECTION WITH THIS FCST
PACKAGE.

FIRST SFC WAVE ACRS NRN IL FCST TO SHIFT INTO MICHIGAN OVRNGT WITH
SCATTERED CONVECTION ASSOCIATED WITH SCNDRY VORT CNTR OVR THE
MISSISSIPPI RIVER SHIFING OVR THE WRN HALF OF THE FCST AREA THIS EVE
BEFORE DISSIPATING. MODELS SUGGEST A LULL IN THE PRECIP LATER THIS
EVENING BEFORE ANOTHER WAVE MOVES ALONG THE FRONT TNT ENHANCING THE
PRECIP...ESP ACRS THE SE HALF OF OUR CWFA. MORE FAVORABLE ENVIRONMENT
FOR HEAVY RAINS ACRS THE SE THIRD OVRNGT AS ETA BUFKIT SOUNDINGS SHOWING
LLJ OF 30-35 KTS...PWAT VALUES APPRCHG 2.00 INCHES AND WARM CLOUD DEPTH
OF 12K FEET. QUESTION BECOMES HOW MUCH OF THE SOUTHERLY INFLOW WL BE
CUTTOFF THIS EVENING FOR RAINFALL FURTEHR NORTH. WL CONTINUE CHC TO
LIKELY POPS ELSEWHERE WITH THE LOWER POPS ACRS OUR FAR NW WITH
PRECIP CHANCES SLOWLY DECREASING ACRS THE NW TOWARDS MRNG. BEST
THREAT FOR RAIN AGAIN ON WED ACRS THE SE HALF AS ANOTHER SHORTWAVE
FORECAST TO MOVE ALONG THE VERY SLOW MOVING BNDRY. WL HOLD OFF ENDING
ANY PRECIP THREAT ACRS THE EAST UNTIL WED EVENING...AND NOT UNTIL THU
MRNG ACRS THE SE AS THE ETA STILL SHOWING ADDL SHORTWAVE ENERGY TO
HOLD UP EWD PROGRESSION OF FRONT. PRECIP CHANCES OUT OF THE SOUTHEAST
BY THU AFTN.

MEDIUM RANGE MODELS STILL SHOWING SOME DISAGREEMENT IN TIMING OF
SHORTWAVE FORECAST TO ROTATE EWD ACRS SRN CAN LATE IN THE WEEK AND
INTO THE WEEKEND. 500 MB HEIGHTS FORECAST TO RISE ACRS THE CNTRL US
DURING THIS TIME FRAME...HOWEVER...STILL TOO CLOSE TO SRN EDGE OF
WESTERLIES TO FEEL REAL CONFIDENT ABOUT TIMING OF PRECIP EVENTS ACRS
THE CWFA. PRECIP CHANCES IN FOR LATER FRIDAY INTO SATURDAY WITH
ENSEMBLES SHOWING HIGHEST PROBS ACRS AREA ON SATURDAY. SEE NO
STRONG REASONING RIGHT NOW TO BE MAKING ANY SIG CHANGES TO EFP.

SPI EB 064/081 063/086 065 44742
PIA EB 063/082 062/085 065 44731
DEC EB 064/081 063/086 065 44742
CMI WB 065/080 062/085 064 44753
MTO TW 066/080 064/085 066 44864
LWV TB 069/083 066/087 067 44985

.ILX...NONE.

SMITH

ILZ027>031-036>038-040>057-061>063-066>068-071>073-131700-

HAZARDOUS WEATHER OUTLOOK FOR CENTRAL ILLINOIS
NATIONAL WEATHER SERVICE LINCOLN IL
1100 AM CDT TUE AUG 13 2002

HEAVY RAINFALL WILL BE POSSIBLE THIS AFTERNOON AND TONIGHT OVER
PORTIONS OF CENTRAL AND SOUTHEAST ILLINOIS.

A SLOW MOVING COLD FRONT OVER EASTERN IOWA WILL MOVE INTO ILLINOIS
THIS AFTERNOON...BRINGING PERIODS OF SHOWERS AND THUNDERSTORMS. THE
AIRMASS OVER THE REGION IS VERY MOIST...SO EXCESSIVE RAINFALL WILL
ACCOMPANY THE STRONGER STORMS. ALTHOUGH NO ORGANIZED SEVERE WEATHER
IS ANTICIPATED ACROSS CENTRAL AND SOUTHEAST ILLINOIS...ISOLATED HAIL
AND GUSTY WINDS ARE POSSIBLE IN STRONGER STORMS THROUGH TONIGHT.

THE STORMS ARE EXPECTED TO CONTINUE INTO WEDNESDAY...ESPECIALLY OVER
CENTRAL AND SOUTHERN ILLINOIS AS THE SLOW MOVING COLD FRONT REMAINS
ACROSS THE REGION.

EH