Severe Thunderstorm Warning 102, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
230 AM CDT THU MAY 17 2000

PLENTY OF FORECAST CHALLENGES AGAIN NEXT 48 HRS. TEMPS...CLOUDS...
PRECIPITATION. ALSO CONCERNED WITH SEVERE WEATHER NEXT 24 HRS ACROSS
CWA.

LATEST 06Z SFC ANALYSIS DEMONSTRATING A STRONG SFC LOW PRESSURE
IN THE CENTRAL PLAINS STATES. SFC WARM FRONT EXTENDED FROM
WESTERN IOWA EAST INTO SOUTHERN WISCONSIN AND EAST INTO
SOUTHERN LOWER MI. SFC COLD FRONT WAS ACROSS SOUTHERN NEBRASKA
SOUTHWEST INTO WEST CENTRAL TEXAS. LATEST IR SATELLITE INDICATING
MID-HIGH LEVEL CLOUDS ACROSS CENTRAL AND SOUTHERN ILLINOIS WITH SOME
LOW-MID LEVEL CLOUDS ACROSS NORTHERN ILLINOIS. LATEST W/V IMAGE
DETECTING SEVERAL WEAK S/W ACROSS MID MISSISSIPPI VALLEY INTO GREAT
LAKES REGION. STRONG S/W WAS CENTERED OVER SOUTHERN NEBRASKA/NORTHERN
KANSAS. LATEST 0715Z KILX RADAR INDICATING SCATTERED THUNDERSTORMS
OVER NORTHERN AND WESTERN CWA MOVING NORTHEAST. KLOT RADAR INDICATING
SCATTERED THUNDERSTORMS ACROSS FAR NORTHERN ILLINOIS/SOUTHERN
WISCONSIN NEAR WARM FRONTAL BOUNDARY MOVING NORTHEAST.

MODELS ARE FAIRLY SIMILAR BUT PLENTY OF DIFFERENCES WERE ALSO
NOTED. WILL GO WITH AN ETA/AVN BLEND SOLUTION. ETA NOT CONSISTENT ON
PLACEMENT OF WARM FRONTAL BOUNDARY LAST 24 HRS...HOWEVER THIS RUN
IT IS MORE IN LINE WITH AVN SOLUTION FOR NEXT 24 HRS. CONFIDENCE IS
BETTER TODAY THEN YESTERDAY ON MODELS. AVN DID FAIRLY WELL ON
LOCATION AND PRECIPITATION PAST 24 HRS. RIDGE ACROSS MISSISSIPPI
VALLEY MOVES EAST NEXT 24 HRS AS TROUGH WILL BE ACROSS GREAT LAKES
SOUTHWEST INTO MISSISSIPPI VALLEY BY 00Z FRI. FOCUS SHIFTS TO SFC LOW
IN CENTRAL PLAINS STATES AS IT MOVES EAST AND IS EXPECTED TO BE
ACROSS CENTRAL ILLINOIS BY 00Z FRI. COLD FRONT IS EXPECTED TO SLAM
INTO WARM AND UNSTABLE AIR ACROSS ILLINOIS THIS AFTERNOON AND
EVENING. ETA MODEL SOUNDINGS PLACING -10 LI/S AND CAPES BETWEEN 3000-
4000 J/KG BY 18Z ACROSS WESTERN CWA. ETA MODEL SOUNDINGS PLACING
LITTLE CAP AND BELIEVE THUNDERSTORMS WILL IGNITE BY EARLY AFTERNOON
ACROSS CWA. THIS WILL CONTINUE INTO EVENING HOURS AS SFC LOW PUSHES
EAST ACROSS CWA. MODEL SOUNDINGS ALSO PLACING SOME DECENT HELICITY
VALUES AND BASED ON LOCATION OF SFC LOW...CWA IS GOOD FOR POSSIBLE
SEVERE WEATHER...INCLUDING POSSIBLE TORNADOES. BELIEVE WE COULD
SEE SUPER CELLS EARLY THEN A POSSIBLE LINE FORMING. AGREE WITH SPC
DAY 1 AND WILL MENTION SVR TSTMS IN FIRST PERIOD OF ZONES. ETA
PLACING HIGH 925MB RH (80-90%) ACROSS CWA THURSDAY NIGHT THROUGH
FRIDAY EVENING. ETA ALSO PLACING DRY AIR ACROSS CWA THURSDAY
AFTERNOON AND EARLY EVENING WHICH WOULD ASSIST THUNDERSTORM ACTIVITY.
ETA PLACES +16 TO +18 H85 TEMPS AT 00Z FRIDAY ACROSS CWA...WITH +10
TO +14 H85 TEMPS BY 12Z FRI...+8 TO +10 BY 00Z SAT. ETA 305K
ISENTROPIC SFC INDICATING ISENTROPIC LIFT TODAY...WITH EXPLOSIVE
ISENTROPIC LIFT BY 00Z FRI ACROSS PARTS OF CWA. ETA CONTINUES SOME
WEAK 305K ISENTROPIC LIFT THROUGH FRIDAY. T/H CROSS SECTIONS ALSO
INDICATING SOME PCPN DEVELOPING THIS AFTERNOON AND INTO FRIDAY. ETA
ALSO PLACES CWA NEAR THE NOSE OF A 50KT H85 LOW-LEVEL JET TODAY.

EXTENDED NO CHANGES MADE AT THIS TIME.

WILL NOT STRAY TOO FAR FROM GUIDANCE. TRICKY PART WILL AGAIN BE CLOUD
DEBRIS AND AMOUNT OF PRECIPITATION ACROSS CWA TODAY...WHICH WILL HAVE
A MAJOR IMPACT ON TEMPERATURES. GO WARMER TODAY AND COOLER TONIGHT.

PRELIMINARY NUMBERS FOR COORDINATION.

SPI TW 082/055 066/049 070 13664
PIA TW 080/052 063/048 068 13674
DEC TW 083/055 066/049 070 13664
CMI TW 083/056 065/050 068 13664
MTO TW 083/056 066/051 071 13664
LWV TW 084/057 070/053 073 13464

.ILX...
IL...NONE.

EH

ILZ027>031-036>038-040>057-061>063-066>068-071>073-181600-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LINCOLN IL
600 AM CDT THU MAY 18 2000

...DANGEROUS SITUATION DEVELOPING TODAY AND INTO THIS EVENING ACROSS
CENTRAL AND SOUTHEAST ILLINOIS...

THERE IS A GOOD CHANCE FOR SEVERE THUNDERSTORMS TODAY AND INTO
THE EVENING ACROSS CENTRAL AND SOUTHEAST ILLINOIS. PRIMARY THREAT
WILL BE TORNADOES...DAMAGING WINDS AND HAIL.

LOW PRESSURE ACROSS THE CENTRAL PLAINS STATES WILL MOVE EAST TODAY
AND IS EXPECTED TO BE ACROSS CENTRAL ILLINOIS THIS EVENING. A COLD
FRONT ASSOCIATED WITH THIS LOW PRESSURE WILL COLLIDE INTO WARM...
MOIST...AND UNSTABLE AIR ACROSS CENTRAL AND SOUTHEAST ILLINOIS TODAY
AND THIS EVENING. THUNDERSTORMS WILL RAPIDLY DEVELOP ALONG AND AHEAD
OF THE COLD FRONT TODAY AND INTO THIS EVENING. EARLY INDICATIONS
SUGGEST SUPERCELLS WILL DEVELOP EARLY...WITH THE POSSIBLE DEVELOPMENT
OF A LINE OF SEVERE THUNDERSTORMS LATER IN THE PERIOD. THIS COULD
BECOME A DANGEROUS SITUATION ACROSS CENTRAL AND SOUTHEAST ILLINOIS...
ESPECIALLY THIS AFTERNOON AND EVENING.

SPOTTER ACTIVATION WILL BE REQUIRED TODAY AND INTO THIS EVENING
ACROSS CENTRAL AND SOUTHEA*ST ILLINOIS. BE ALERT TO THE RAPIDLY
CHANGING WEATHER CONDITIONS.

HOLICKY