Severe Thunderstorm Warning 153, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 AM CDT TUE JUN 20 2000

FCST CHALLENGES THIS PD WL BE TIMING OF FROPA ACRS FCST AREA AS WELL
AS SVR POTENTIAL LT THIS AFTN AND TNT AHD OF BOUNDARY.

MODELS DID A FAIRLY DECENT JOB INITIALIZING THIS MRNG WITH ETA AND
AVN SEEMING TO HAVE THE BEST HANDLE ON THE DEEPENING UPPER TROF ACRS
THE NRN ROCKIES AS WELL AS THE WEAK VORT LOBE APPRCHG IL FROM THE
CNTRL PLAINS THIS MORNING. 06Z SFC ANALYSIS INDICATING FAIRLY
IMPRESSIVE 3 HOURLY PRES FALLS ACRS NWRN WI SOUTHWEST THRU IA. BEST
THETA-E ADV AND UPPER LVL DIVERGENCE LOCATED ACRS THE ERN DAKOTAS
INTO NRN IA SOUTH INTO NRN KS WHERE STRONGEST CONVECTION WAS
OCCURRING THIS MRNG. TIME HEIGHT CROSS SECTIONS SUGGEST BEST LAYERED
OMEGA OCCURRING ACRS THE FCST AREA UNTIL EARLY AFTERNOON IN
ASSOCIATION WITH WEAK VORT LOBE...WITH A SECONDARY PEAK LATER THIS
EVENING AHD OF COLD FRONT. 65 TO 70 DEG DEW POINTS STREAMING NWD
INTO THE MIDWEST WITH SAT DERIVED PWATS IN THE 1.75 TO 2 INCH RANGE
TO OUR SOUTH...SO ANY OF THESE STORMS COULD PUT DOWN QUITE A BIT OF
WATER IN A SHORT PERIOD OF TIME. BIGGEST CONCERN WL BE EXTENT OF
CLOUDS AND PRECIP AND HOW IT WILL AFFECT OUR SVR THREAT LATER THIS
EVENING. TIME HEIGHT CROSS SECTIONS SUGGEST LOW LVL MOISTURE INCRG
WITH TIME THIS MRNG WITH NOT MUCH BREAK UP INDICATED DURING THE DAY.
SHOULD SEE SOME BREAKS DVLP FOR A TIME EARLY THIS AFTN TO SEE TEMPS
PUSH UP CLOSE TO FWC GUID WHICH WOULD YIELD CAPES IN THE 1500-2000
J/KG RANGE BY THIS EVENING. FCST HODOGRAPHS INDICATE SOME LOW LVL
TURNING OF WINDS (0-3KM) THIS EVENING AHD OF FRONT...HOWEVER IT
APPEARS MAIN THREAT WITH THE STORMS THIS EVENING WILL BE DAMAGING
DOWNBURST WINDS AND HEAVY RAINFALL.

AS STRONGER VORT CNTR ROTATES ACRS THE NRN MIDWEST LATER TODAY...COLD
FRONT SHOULD CONTINUE ITS EWD PROGRESSION. AWIPS DPROG/DT FUNCTION
SUGGESTING A SLOWER MOVMNT TO FRONT...ESP AS IT GETS INTO CNTRL AND
ERN IL EARLY WED MORNING. ETA MODEL INDICATING SFC WAVE DVLPG ACRS
THE SRN PLAINS FOCUSING AN AREA OF STRONG LOW LVL CONVERGENCE ALONG
ADVANCING COLD FRONT TO OUR SOUTHWEST OVERNIGHT. QUESTION BECOMES IF
THIS DOES OCCUR WL IT IMPEDE ON MOIST INFLOW INTO OUR AREA AHD OF
FRONT AND CUT DOWN PRECIP AMTS?  00Z UA ANALYSIS INDICATING STRONGER
BAND OF WINDS STILL ON THE WEST SIDE OF DVLPG TROF TO OUR WEST SUGGESTING
A SLOWER PROGRESSION OF FEATURE NEXT 36 HRS...AS A RESULT...WL BE
KEEPING HIGHER POPS GOING AT LEAST THRU WED MRNG OVR THE FAR EAST
AND SOUTHEAST COUNTIES. AVN MODEL THE MOST AGGRESSIVE IN BRINGING
SECONDARY VORT LOBE ACRS THE MIDWEST LATE ON WED BUT WITH DEEP LAYERED
MOISTURE SHUNTED TO OUR SOUTH AND EAST...WL GO WITH THE "DRYING"
TREND GOING OVR MOST OF THE FCST AREA.

STILL A COMPLICATED PICTURE AS FAR AS THE EXTENDED IS CONCERNED.
PROGRESSIVE FLOW PATTERN TO CONTINUE MOST OF THE WEEK WITH SHORTWAVE
ENERGY FCST TO PUSH INTO THE MIDWEST AGAIN OVR THE WEEKEND. BOUNDARY
WHICH SLIPS TO OUR SOUTH ON WED WILL BEGIN TO SLOWLY APPRCH AREA
LATER ON FRIDAY AND BE IN AREA ON SAT AS UPPER LVL ENERGY APPRCHS.
BASED ON LATEST ECMWF AND UKMET MODELS...WILL INTRODUCE TSRA CHANCES
ON SAT AS SYSTEM APPROACHES STATE.

PRELIMINARY CCF FOR COORDINATION PURPOSES ONLY...

SPI TB 084/064 080/057 080 44863
PIA TB 082/063 079/056 079 44863
DEC TB 084/064 080/057 080 44863
CMI TB 082/064 079/057 078 44774
MTO TW 084/067 081/058 080 44676
LWV TW 086/072 082/069 082 44687

.ILX...NONE.

SMITH

ILZ027>031-036>038-040>057-061>063-066>068-071>073-201800-

HAZARDOUS WEATHER OUTLOOK FOR CENTRAL ILLINOIS
NATIONAL WEATHER SERVICE LINCOLN IL
1100 AM CDT TUE JUN 20 2000

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND TONIGHT...WEST OF A KANKAKEE TO DECATUR LINE.

SHOWERS AND THUNDERSTORMS WERE OCCURRING OVER PARTS OF CENTRAL
ILLINOIS THIS AFTERNOON...WITH A WARM UNSTABLE AIRMASS IN PLACE. AN
AREA OF LOW PRESSURE WILL TRACK WELL TO THE NORTH OF ILLINOIS DURING
THE DAY PUSHING A COLD FRONT TO THE MISSISSIPPI RIVER BY EARLY THIS
EVENING. THE ATMOSPHERE AHEAD OF THE COLD FRONT IS EXPECTED TO
DESTABILIZE THIS AFTERNOON WITH THUNDERSTORMS FORECAST TO
CONTINUE AHEAD OF THE FRONT. SOME OF THESE THUNDERSTORMS COULD
BECOME SEVERE LATER THIS AFTERNOON OR EVENING. AT THIS TIME...THE
PRIMARY THREAT WITH THESE STORMS WILL BE DAMAGING DOWNBURST WINDS AND
VERY HEAVY RAINFALL.

SPOTTER ACTIVATION MAY BE REQUIRED LATER THIS AFTERNOON AND
EVENING IN THE SPRINGFIELD AND PEORIA AREAS.

KETCHAM