079 
FXUS63 KILX 180838
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
330 AM CDT WED JUL 18 2001

FORECAST CONCERNS ARE WITH RESPECT TO PCPN CHCS AND PSBLTY OF STRONG 
STORMS/HEAVY RAIN.

CONVECTION CURRENTLY IN ERN PARTS OF FORECAST AREA IS ELEVATED IN 
NATURE AS 20-25 KT LOW LEVEL JET INTERSECTS A BOUNDARY THAT WAS 
ROUGHLY FROM SOUTH OF DSM-UIN-XTRM SW IND. THIS CONVECTION IS XPCTD 
TO CONTINUE PAST DAYBREAK...THEN DISSIPATE AS LOW LEVEL WINDS AND 
CONVERGENCE FCST TO WEAKEN. MCS IN IOWA IS HOLDING TOGETHER AND WILL 
BE THE FOCUS FOR DEVELOPING T-STORMS IN WCENT IL TODAY. THE MID 
LEVEL SHORTWAVE ASSOCIATED WITH IT/MCS REMNANTS WILL SLIDE INTO CENT 
IL LATE THIS MORNING/ERLY AFTN. PLENTY OF INSTABILITY WITH CAPES 
OVER 4000 AND LI/S UP TO -9. LOW LEVEL SHEAR/DEEP LAYER SHEAR NOT 
VERY IMPRESSIVE...BUT HIGH INSTABILITY AND PROXIMITY OF NW-SE 
ORIENTED SFC BOUNDARY FROM SW IA-CENT/SE IL COULD PRODUCE STORMS WITH
STRONG WIND GUSTS. 

AM ALSO CONCERNED THAT WITH AFOREMENTIONED BOUNDARY...LOW LEVEL 
CONVERGENCE...INCRSG UPR LEVEL DIVERGENCE AND DEEP MOISTURE 
(PRECIPITABLE WATER VALUES GRTR THAN 2 INCHES) TRAINING CELLS WITH 
LOCALLY HEAVY RAIN A DISTINCT POSSIBILITY. FLASH FLOOD GUIDANCE IS 
RELATIVELY HIGH...SO WILL HOLD OFF ON HEADLINE BUT WILL MENTION 
LOCALLY HEAVY RAIN ACROSS FORECAST AREA.

TEMPS WILL BE TRICKY TODAY DUE TO ONGOING CONVECTION IN ERN IL AND 
ADVANCING CONVECTIVE COMPLEX/ASSOCIATED CLOUD COVER. WILL FOLLOW THE 
LEAD OF THE NUMERICAL GUIDANCE AND LOWER TEMPS A FEW DEGREES FROM 
YESTERDAYS HIGHS...WITH UPR 80 AND HEAT INDICES AROUND 100. 

WILL BUMP UP POPS FOR SRN PARTS OF FORECAST AREA TONIGHT...AND KEEP
40 POPS GOING IN NRN SECTIONS AS A BOUNDARY SLIDES SOUTH IN RESPONSE 
TO INCREASING NE FLOW IN GRT LAKES STATES. MODELS INDICATE AN MCS 
XPCTD TO DEVELOP IN NRN MO TRACKING INTO SCENT IL OVERNIGHT. THE 
BOUNDARY IS XPCTD TO SLIDE A BIT FARTHER SOUTH THURSDAY...BUT WILL 
KEEP CHC POPS GOING FOR WHOLE CWA SINCE TEMPS/MOISTURE NOT XPCTD TO 
CHANGE MUCH AND UNCERTAINTY OF BOUNDARY POSTIONS COULD PROVIDE FOCUS 
FOR CONVECTION.

WILL UPDATE EXTENDED FORECAST TO DROP PCPN MENTION FOR FRIDAY AND 
SATURDAY AS UPR RIDGE BUILDS IN UPR MIDWEST...WHICH SHOULD CAUSE 
CONVECTION TO STAY FAR ENOUGH WEST AND NORTH OF REGION.

THANKS TO LOT/LSX FOR COORDINATION.

...PRELIMINARY CCF FOR COORDINATION PURPOSES ONLY...

SPI TB 089/073 088/073 087 23664
PIA TB 088/072 088/073 087 23643
DEC TB 087/073 088/072 087 23664
CMI TB 088/072 087/072 086 23643
MTO TB 086/072 087/072 086 23664
LWV TB 087/073 088/073 087 23664

.ILX...NONE.

$$

MILLER