Severe Thunderstorm Warning 20, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
245 PM CDT MON APR 9 2001

ETA/MESOETA WL BE USED IN THE SHORT TERM FORECAST PERIOD AS SVL MESOSCALE
BOUNDARIES FROM MRNG CONVECTION LOCATED OVER CNTRL IL WHICH WILL AID IN
DVLPMT OF NEW CONVECTION LATER THIS AFTERNOON AND EVENING. MAJOR WEATHER
SYSTEM COMING OUT OF THE SOUTHWEST MIDWEEK WAS HANDLED THE BEST BY THE
AVN AND WILL FOLLOW ITS SOLUTION LATER IN THE FORECAST PERIOD. MAIN
FORECAST CHALLENGE THIS PD WL BE DURATION AND AEREAL EXTENT OF
PRECIP OVR CNTRL IL INTO TUE ALONG WITH TEMPS.

18Z MESOANALYSIS INDICATING WEAK SFC WAVE OVR SE IOWA WITH BNDRY EXTDG
EWD TO SECONDARY WAVE OVR NW OHIO. SVL CONVECTIVE BOUNDARIES LOCATED
ACRS THE CWA. ONE BNDRY IS ACTUALLY RETREATING NEWD INTO SW IL WHERE
THE 18Z MSAS WAS INDICATING SOME WEAK CONVERGENCE ALONG IT. SECONDARY
BNDRY EXTDG FROM SFC WAVE OVR ERN IA TO NEAR GALESBURG TO JUST SOUTH
OF MARSEILLES. MSAS SUGGESTING BEST MOISTURE CONVERGENCE NEAR SFC
WAVE OVR ERN IA. 18Z ILX SOUNDING INDICATING NO CAP WITH CAPES APPRCHG
2500 J/KG. MODELS ONCE AGAIN SLOW TO DEVELOP CONVECTION ACRS THE CWA
THIS AFTN WITH MAIN ACTION DEVELOPING TNT AS LOW LVL JET INCREASES
TO OUR SOUTHWEST AND IMPEDES ON BNDRY ACRS CNTRL IL. WATER VAPOR LOOP
SHOWING SUBTROPICAL PLUME TRACKING NEWD OUT OF THE SRN PLAINS EARLY
THIS AFTERNOON WITH MODELS DEPICTING IMPRESSIVE 250 MB DIVERGENCE
ACRS THE FORECAST AREA LATE TNT INTO TUE. WL HIT THE PRECIP WORDING
HARD WITH A MENTION HEAVY RAINFALL LATER TNT INTO TUE MRNG. DON'T
FEEL VERY CONFIDENT ABOUT WHERE AXIS OF HEAVIEST RAINFALL WL BE
LATER TNT AS ANY CONVECTION WHICH FIRES NEAR SYNOPTIC BNDRY MAY TEND
TO PUSH FRONT FURTHER SOUTH THAN INDICATED BY THE ETA/MESOETA. FFG
VALUES STILL RELATIVELY HIGH ACRS THE CWA SO FOR NOW WL HOLD OFF ANY
FF WATCH HEADLINES. GUID NUMBERS SEEM MORE IN LINE THIS FCST CYCLE
THAN IN THE PAST AND WL STAY CLOSE TO THOSE TNT.

FORECAST BECOMES EVEN MORE COMPLEX TMRW AS ETA/MESOETA SUGGEST BNDRY
WL NOT PUSH VERY FAR SOUTH ACRS OUR CWA...AS A RESULT WL KEEP PRECIP
CHANCES GOING ON TUE OVR MOST OF THE CWA. TUE NIGHT AND WED...AS NEXT
MAJOR SHORTWAVE PULLS OUT INTO THE HIGH PLAINS...STRONG LOW LVL
WARM ADVECTION PATTERN DEVELOPS ACRS THE MIDWEST AS 60+ KNT LOW LVL
JET PULLS DEEP MOISTURE NWD INTO THE REGION. LIKE THE AVN'S DEPICTION
OF PULLING STRONG SFC LOW WELL TO THE WEST OF THE CWA AS ADDL
SHORTWAVE ENERGY DROPS INTO THE MEAN LNGWV TROF POSITION LT WED. THIS
SHOULD RESULT IN ANOTHER THREAT OF CONVECTION TO THE CWA LT WED INTO
EARLY THUR MRNG ALONG WITH STRONG GRADIENT WINDS.

THANKS TO LSX AND IND FOR THE COORD THIS AFTN.

...PRELIMINARY NUMBERS FOR COORDINATION ONLY...

SPI TB 057/072 055/078 055 44766
PIA TB 054/070 055/077 053 44656
DEC TB 057/072 055/078 055 44766
CMI TB 055/073 054/078 055 44666
MTO TB 061/077 062/079 055 55766
LWV TB 065/080 064/082 059 44765Z

.ILX...NONE.

SMITH