Tornado in Illinois, May 1, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
400 AM CDT WED MAY 1 2002

CONCERNS FOR THIS FCST PD...

MDT RISK SVR TSTMS OVR MOST OF CWA TDA/THIS EVE
HVY PCPN
TEMP FCSTS
FOG

SFC LOW NOW OVR NRN OK FCST TO DPN AND LIFT NEWD ACRS E CNTRL MO
THIS AFTN AND INTO IN TNGT.  MODELS STILL DIVERGE AS TO LOCATION OF
SFC LOW CNTR AS IT LIFTS ENEWD TWD INDIANA TNGT. ETA STILL FURTHEST
SOUTH AND NGM/AVN STILL HOLDING IT FURTHER N. PROB IS THAT DENSE FOG
HAS FORMED N OF WRM FNT ACRS SRN THIRD MO.

SGFNT SVR WX FCST TO DVLP NR SFC LO AND ALG/NR WRM FRONTAL
BOUNDARY.  SPC HAS OUTLOOKED MOST OF CWA IN MDT RISK FOR TDA AND
TNGT.  THIS FOG DVLPMT HAS COMPLICATED MATTERS AS ELY FLOW N OF LOW
WL TEND TO HOLD IT IN AND MID/HI CLDS BEGINNING TO DEVELOP OVR WRN
MO OVERHEAD TO EXASTERBATE THE PROBLEM. CURRENT PRES FALLS STILL IN
OK NEAR LOW AS IT BEGINS TO DEEPEN SLOWLY.

MODELS ALL DVLP PCPN IN COLD AIR OVR NRN MO/CNTRL IL TDA AND THIS EVE
BUT DO LITTLE IN THE WARM AIR...HWVER COND WILL CONTINUE TO HEAT UP
AND DEVELOP W/TIME TDA. HAVE OPTED TO FOLLOW AVN MODEL AGAIN TODAY
AND ALLOW WRM FNT TO LIFT NWD AS LOW DEEPENS NEWD.  PROB IS WHAT TO
DO WITH FOG/LOW CLDS N OF LOW.  LOOKS LIKE THIS MAY LIFT NWD INTO E
CNTRL MO/SRN IL FOR AWHILE THIS MRNG. HV MODIFIED TEMPS DOWN A BIT
DUE TO COLD AIR PLACEMENT AND THE EWD ORIENTATION OF LLJ.

OFFICE HAS SET UP A STAFFING PATTERN FOR SGFNT SVR WX EPISODE THIS
AFTN/EVE.

NEXT THING IS HVY PCPN. FLOOD GUIDANCE LESS THAN 2 INCHES IN MOST
AREAS AND 1.00 TO 1.50 IN MANY PLACES...PCPBL WATER TOTALS ARE
UNSEASONABLY HIGH HWVR CELL MVMTS WILL BE RAPID AND LOCATION STILL
IN DOUBT...SO WILL MENT LOCALLY HEAVY AMOUTS IN IL ZONES BUT NO
HIGHLIGHTS FOR FLOODING.

STILL IN A QUANDRY ABOUT TEMPS...60S NORTH...FOG MAY HOLD AREAS
ALG/NR I-70 AROUND 70 DEG WITH WELL INTO 80S SOUTH.  IF LOW TREKS
ALG AVN  FCST GUIDELINES LOOK FOR SKIES TO CLEAR AND TEMPS TO JUMP
QUICKLY.

FOG....WL MENT DENSE FOG OVR SRN ZONES THIS MRNG BUT NOT ISSUE AN
ADVISORY AS DAYLIGHT WILL ALLOW FOR BETTER DRIVING VISIBILITIES
QUICKLY.

.STL...NONE

PEDIGO

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-011800-

HAZARDOUS WEATHER OUTLOOK...CORRECTION...OUTLOOK IS FOR THURSDAY
NATIONAL WEATHER SERVICE ST LOUIS MO
615 AM CDT WED MAY 1 2002

THREATS THROUGH TONIGHT...
THERE IS A SIGNIFICANT THREAT FOR A SEVERE WEATHER OUTBREAK TODAY
AND TONIGHT FOR MUCH OF THE AREA. THERE IS A MODERATE RISK FOR
SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING ACROSS MUCH OF
EASTERN MISSOURI AND SOUTHERN ILLINOIS ALONG AND SOUTH OF A LINE
FROM JEFFERSON CITY TO 40 MILES NORTH OF ST LOUIS TO JUST NORTH OF
EFFINGHAM ILLINOIS. THIS INCLUDES MOST OF THE FORECAST AREA.
THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND
TONIGHT FURTHER NORTH THAT INCLUDES MUCH OF NORTHEAST MISSOURI
AND THE REMAINING WARNING COUNTIES OF CENTRAL ILLINOIS. THE AREA
COVERED INCLUDES ALL COUNTIES NORTH OF THE LINE OF DELINEATION FOR
MODERATE RISK OF SEVERE WEATHER AND SOUTH OF A LINE FROM MOBERLY
MISSOURI TO HANNIBAL AND EAST NORTHEAST TO ABOUT 10 MILES NORTH OF
SPRINGFIELD ILLINOIS. THIS MEANS THE ONLY AREA NOT COVERED BY THIS
OUTLOOK IS A FEW COUNTIES IN EXTREME NORTHEAT MISSOURI AND THE
QUINCY AREA. THESE AREAS MAY BE A LITTLE TOO FAR NORTH AND REMAIN
IN THE COLDER AIR THAT WILL DIMINISH THE THREAT OF SEVERE WEATHER
FOR THAT AREA.

DISCUSSION...
A STORM SYSTEM IS FORMING OVER THE CENTRAL PLAINS THIS MORNING.
THE LOW PRESSURE CENTER WAS LOCATED IN NORTH CENTRAL OKLAHOMA EARLY
TODAY WITH A WARM RONT PIVOTING EAST FROM THE LOW THROUGH NORTHERN
ARKANSAS AND INTO WESTERN TENNESSEE. CURRENT INDICATIONS ARE THAT
THE LOW WILL DEEPEN AND RACE EAST NORTHEAST THROUGH CENTRAL MISSOURI
...CENTRAL ILLINOIS...AND INTO INDIANA BY LATE TONIGHT.  AS IT DOES
WARM AIR WILL SURGE NORTHWARD WITH THE LEADING EDGE OF THE WARMER
AIR FORMING A FOCUS POINT EAST TO WEST ACROSS MISSOURI AND ILLINOIS.

A SIGNIFICANT SEVERE WEATHER EPISODE APPEARS TO BE SETTING UP FOR
THIS AFTERNOON AND EVENING ACROSS A LARGE PORTION OF CENTRAL AND
SOUTHERN MISSOURI AND ILLINOIS AS WELL AS SOUTHWESTERN INDIANA AND
WESTERN KENTUCKY.KTUDKA DEVELOPING FRONT ACROSS SOUTHERN MISSOURI
AND ILLINOIS WILL BE THE FOCUS OF THUNDERSTORMS THIS AFTERNOON AND
TONIGHT.  WARM AND UNSTABLE AIR DRAWN NORTHWARD ALONG AND OVER THE
FRONT WILL PROVIDE THE POTENTIAL FOR THUNDERSTORMS.  SOME OF THESE
STORMS WILL BE SEVERE ...WITH LARGE HAIL...DAMAGING WINDS...AND
A FEW TORNADOES POSSIBLE. THESE COULD FORM AT ANY TIME TODAY AND
WILL LIKELY BECOME SEVERE WITHIN A A FEW SHORT MINUTES. THIS WILL
REQUIRE AN ADDED STATE OF READINESS ON THE PART OF EVERYONE
TODAY...COORDINATORS...SPOTTERS...MEDIA...AND FORECAST STAFF AT THE
NATIONAL WEATHER SERVICE.  THE PUBLIC SHOULD KEEP ONE EYE ON THE
SKY AND BE ABREAST OF LOCAL STATEMENTS AND POSSIBLE WATCHES OR
WARNINGS.

IT WOULD ALSO BE GOOD TO KEEP IN MIND THAT TODAYS WEATHER WILL
BE RATHER DECEIVING. SKIES WILL LIKELY BE GREY WITH LOW CLOUDS
AND FOG IN THE AREA.  YOU WILL PROBABLY NOT BE ABLE TO SEE THE
STORMS APPROACHING...THEY COULD BE SHROUDED FROM VIEW. THIS WILL
MAKE IT EVEN MORE PERTITENT AND IN ESSENCE, EVEN MORE DANGEROUS
TO THE AVERAGE PERSON AS WELL AS SPOTTERS ALIKE.

EMERGENCY MANAGERS SHOULD REMAIN ON A HIGH STATE OF AWARENESS
THE NEXT 24 HOURS AS SKYWARN ACTIVATION IS LIKELY.  IF FOR ANY
REASON YOU WILL BE UNABLE TO BE A PART OF IT...MAKE EARLY CONTACTS
FOR SOMEONE TO TAKE YOUR PLACE OR ASSIST YOU.

 .OUTLOOK FOR THURSDAY...

THE STORMS THAT ARE EXPECTED TODAY AND TONIGHT WILL RACE ON TO THE
EAST OF THE AREA FOR WEDNESDAY AND COLDER MORE STABLE AIR WILL
OVERTAKE THE AREA...HOWEVER THERE WILL BE ANOTHER SIGNIFICANT THREAT
OF SEVERE WEATHER POSSIBLE THIS WEEKEND.  KEEP YOUR PLANS FLEXIBLE
ACCORDINGLY.

PEDIGO

THIS PRODUCT WILL BE ISSUED BETWEEN 6 AND 8 AM DAILY...AND WILL BE
UPDATED AS NEEDED.  FOR DETAILED INFORMATION ON A PARTICULAR
THREAT...MAKE SURE TO REFER TO THE ZONE FORECASTS AND THE ACTUAL
WATCH...WARNING OR ADVISORY PRODUCT.