Severe Thunderstorm Warning 140, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
245 PM CDT TUE JUL 24 2001

SFC ANALYSIS SHOWS THAT WINDS ARE STILL MAINLY OUT OF THE SOUTH AS
MAIN SYNOPTIC COLD FRONT IS STILL LOCATED ACROSS NRN IA. THIS IS
MUCH SLOWER THAN PREVIOUS MODEL RUNS.  UPR AIR ANAL SHOWS MESO
INDUCED VORT MOVING ACROSS IA BASICALLY HOLDING UP SRN PROGRESSION
OF FRONT TOWARDS IL.  LOTS OF LOW LVL MOISTURE ACROSS CEN IL AND NRN
MO WITH SFC DWPTS AGAIN IN THE UPR 70S.

QUESTIONS TDY WILL BE TSRA CHC TNGT AND WED. MODELS FAIRLY SIMILIAR
WITH UPR LVL FEATURES AND SFC FEATURES. MODELS DO NOT SHOW MUCH IN
THE WAY OF LOW LVL FOCUSING MECHANISM AROUND FOR TSRA CHC THIS EVE.
BUT WITH LOTS OF INSTABILITY AROUND AND WK OUTFLOWS LURKING ABOUT
...CANNOT RULE OUT SOME ISOLD TSRA THIS EVE. BUT BELEIVE ORGANIZED
CONVECTION WILL WAIT UNTIL LATE TNGT AS VORT MAX IN CEN IA MOVES
INTO NRN IL.  THIS VORT MAX AND DVLPG SFC LOW PRESS AREA IN ERN IA
WILL INCREASE LIFT ENOUGH FOR TSRA CHCS INCREASING ACROSS CEN IL
LATE TNGT MAINLY AFTER MIDNIGHT. WILL MAKE A PRESS TIME DECISION ON
ANY CATEGORICAL POPS THIS EVE...WITH MAIN EMPHASIS ON TIMING OF
OVERNIGHT PCPN CHC.  LOTS OF INSTABILITY AROUND FOR SVR WX POTENTIAL
EARLY MORN WED SO MID SHIFT WILL HAVE TO KEEP AN EYE ON THINGS...BUT
MAIN UPR LVL SUPPORT REMAINS ACROSS NRN IL. LOW TEMPS WL CONTINUE TO
BE ON THE WARM SIDE AS FRONTAL BOUNDARY HOLDS OFF UNTIL WED.  GUID
NUMBERS SIMILIAR AND WILL FOLLOW.

THE DVLPG LOW PRESS SLIDES E/SE ACROSS CEN IL WED MORNING WITH THE
TRAILING COLD FRONT FINNALY MAKING ITS WAY ACROSS IL. LIFT PROVIDED
BY THE S/WV LOBE AND SFC LOW PRESS AREA AND CONVG ALONG THE FRONT
WILL PROVIDE MOST OF CEN IL WITH A PRETTY GOOD SHRA/TSRA CHC WED.
INSTABILITY ALSO WILL BE IN PLACE FOR A CONTINUED SVR WX CHC. SO
WILL CONTINUE THE LIKELY POPS ACROSS MOST OF CEN IL WED...WITH CHC
POPS FURTHER SE.  ANOTHER VORT MAX PROGRESSES EWRD IN THE ZONAL UPR
FLOW INTO CEN IL BY WED AFTN...THIS WILL PROVIDE ENOUGH PUSH TO THE
FRONT TO MOVE IT SOUTH ACROSS CEN IL BY 00Z/THU.  SO LOOKS LIKE MOST
OF THE SHRA/TSRA ACTIVITY WILL END IN THE EARLY EVE WED. HIGH TEMPS
WED COULD BE INTERESTING...AS SFC FRONT IS DELAYED UNTIL WED AFTN.
WILL ADJUST SPI ZONE TO RAISE TEMPS SLIGHTLY.  NOTICABLY
COOLER/DRIER AIR WILL RETURN TO CEN IL BEHIND THIS SYS WITH LOW
TEMPS DROPPING INTO THE L60S. PREFER COOLER FAN/MAV NUMBERS FOR
THIS.

THING DRY OUT FOR THU INTO THE FIRST PART OF THE EXTENDED...AS A SFC
HIGH PRES RIDGE SLIDES ACROSS THE GRT LKS.

MRF SHOWS NEXT CHC FOR PCPN LOOKS TO BE SUN-TUE AS SFC RIDGE SLIDES
EAST...RETURNING SUBTROPICAL AIRMASS TO CEN IL.  HARD TO PINPOINT WK
IMPULSES IN THE ZONAL UPR FLOW...WILL PROVIDE TSRA CHC EACH DAY WITH
UNSTABLE AIRMASS IN PLACE.

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

SPI TB 071/085 064/081 058 22662
PIA TB 070/081 062/079 057o 22762
DEC TB 071/085 064/081 059 22662
CMI TB 070/081 063/079 057 22662
MTO TB 071/083 065/082 060 22666
LWV TB 072/088 067/082 060 22666

.ILX...NONE.

KETCHAM