Severe Thunderstorm Warning 209, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
240 PM CDT SUN JUL 2 2000

FORECAST CONCERNS THIS PD WL BE EXCESSIVE RAINFALL POTENTIAL ACRS
OUR NRN AND ERN CWA TNT AND MOVMT OF SYNOPTIC BNDRY OUT IN TIME.

18Z SFC MAP DEPICTING CDFNT ACRS SRN MN INTO CNTRL WI...SLOWLY
SINKING SWD. MESOSCALE BNDRY FROM PREVIOUS CONVECTION ACRS NRN
IL PRODUCING SOME ISOLD TSRA MAINLY ACRS THE NORTH. IMPRESSIVE
RISE/FALL COUPLET LOCATED FROM SRN MN INTO SRN WI WITH BEST
INSTABILITY/LL CONVERGENCE AND 850 MB WARM AXIS INTO NERN IA
SRN WI AND NRN IL. WEAK SHORTWAVE THAT PRODUCED THE CONVECTION ACRS
OUR SRN COUNTIES THIS MRNG HAS SHIFTED EAST AND SOUTH OF FCST AREA
THIS AFTERNOON. ETA MODEL AGAIN HAS DONE A RELATIVELY GOOD JOB WITH
THE SMALLER SCALE FEATURES FROM OUR MRNG CONVECTION...ALTHOUGH THE
QPF FIELDS WERE A BIT TOO FAR NORTH AND TOO SLOW IN ITS EWD PROGRESSION.
SYNOPTIC SCALE BOUNDARY TO SHIFT SLOWLY SOUTH TNT WITH MAIN CONVECTION
EXPCTD ALONG AND JUST SOUTH OF FNT IN VERY MOIST AND UNSTABLE AIR MASS.
PWAT VALUES NEAR 2 INCHES TNT JUST TO OUR NORTH NEAR BNDRY WITH SATURATION
THICKNESSES SUGGESTING 1.5-2 INCHES PSBL NORTH OF 573-576 THICKNESS
CHANNEL...WHICH WOULD BE FM KGBG-KBMI-KCMI. NEW FFG ACRS CWA ARE IN THE
2-2.5 INCH RANGE OVR MOST OF THE AREA EXCEPT OUR FAR SOUTHEAST SO FOR NOW
WL HOLD OFF ISSUING ANY FFA.

CDFNT FCST TO STALL OUT OVR CNTRL IL BY NOON TUE AND BEGIN A NWD TRACK
AGAIN BY AFTN AND EVENING AS NEW SHORTWAVE PULLS OUT INTO THE PLAINS AND
FOCUSES INSTABILITY AND RAINFALL THREAT TO OUR WEST AND NORTH FOR MON
NIGHT AND TUE. NOT REAL CONFIDENT ABT MOVMT OF BNDRY ON TUE INTO TUE
EVE...SO WL CARRY POPS THRU THE DAY RATHER THAN KEEP THE MORNING
WORDING. ETA DEPICTING BEST INSTABILITY AND 925 MB FRONTOGENETICAL
FORCING PROGGED TO SHIFT INTO SERN MN AND WI BY EVENING...HOWEVER DUE
TO UNCERTAINTY OF BNDRY LOCATION...WL KEEP AT LEAST SOME LOW POPS GOING
INTO THE THIRD PD. FAN GUID NUMBERS HAVE BEEN MORE CONSISTENT OVR THE
PAST SVL RUNS AND WL STAY FAIRLY CLOSE TO THOSE THIS FCST PD.

MRF NOT AS AGGRESSIVE IN DEVELOPING DEEP TROF OVR THE LKS IN LATER PDS
AS IT WAS YSTDY. ECMWF STILL BULLISH ON DVLPG UNSEASONABLY DEEP TROF
ACRS THE ERN LAKES WITH RIDGING SHIFTING ACRS THE ROCKIES. HOWEVER...
ADDL SHORTWAVE ENERGY RIDING OVR TOP OF CNTRL US RIDGE WL KEEP BNDRY
RELATIVELY CLOSE TO FCST AREA...SO RATHER THAN TRYING TO BE CUTE WITH
WORDING IN OUR EXTENDED...WL INCLUDE CHANCES OF PRECIP INTO FRI.

PRELIMINARY CCF FOR COORDINATION PURPOSES ONLY...

SPI BB 071/086 070/088 069 44543
PIA BB 069/084 068/086 067 44644
DEC BB 071/086 070/088 069 44543
CMI BB 070/086 069/087 068 44644
MTO BB 071/088 071/088 070 44443
LWV BB 072/089 072/089 072 44333

.ILX...NONE

SMITH