Severe Thunderstorm Warning 27, NWS Paducah, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
200 PM CDT FRI MAY 11 2001

COMPLEX ARRAY OF PARAMETERS TO TRACK THAT MAY INFLUENCE PAHS 1ST
PERIOD WX. ONE ITEM OF CONCERN IS ONGOING SEMO CONVECTION...WITH
LATEST IR TRENDS SHOWING TOPS STARTING TO COOL OUT OF WHAT WAS
OTHERWISE THIS AM WARM TOPPED CONVECTION. THIS EVOLUTION WAS
OCCURRING/LIKELY AIDED BY NE AR VORT MAX THAT IS MOVING EAST...BUT
IT IS FORECAST TO SHEAR OUT WITHIN DIFLUENT 1000-500MB THICKNESS
FIELD. EFFECTS OF THIS DIFLUENCE SEEN MOST DRAMATICALLY BY SW FEED
OF COOLING TOPS FM MAIN BODY OF CONVECTION OVER SW MO/NW AR.

ONE EFFECT OF EARLY PM SEMO CONVECTION COULD BE TO NEUTRALIZE
DEVELOPMENT OF MODERATELY UNSTABLE STORM ENVIRONMENT OVER SEMO/FAR
WKY. MAIN AREA OF CONCERN TONIGHT THEN BECOMES NRN/ERN PTNS
FA...WHERE VIGOROUS SHORT WAVE UPSTREAM WILL DRIVE COLD FRONT ACROSS
FA LATE THIS PM/EARLY THIS EVENING. BASED ON LATEST VISIBLE
SATELLITE TRENDS...IT APPEARS THIS IS ALSO THE AREA WHERE BEST LOW
LAYER DESTABILIZATION WL OCCUR...SO WL LIKELY GO WITH HIGHEST POPS
THERE...TAPERING OFF TO LOWER CHC SOUTH AND WEST. ITS ALSO WHERE
OUR HIGHEST CONCERN FOR SVR THREAT WL BE...THOUGH ENTIRE CWA IS
JUSTIFIABLY IN SLGT RISK.

ETA/AVN HAVE BEEN SYNCHRONIZING LAST COUPLE OF RUNS AND APPEAR TO BE
IN GENERAL AGREEMENT NOW...WITH FROPA THRU JUST ABOUT ENTIRE FA BY
06Z. SOME CONCERN HERE AS BOTH MODELS NOW HINT AT BREAKING OFF
PRIMARY MRH FIELDS TO OUR NORTH AND SOUTH...A CLIMATOLOGICALLY
RATHER FREQUENT OCCURRENCE. HOWEVER WITH APPROACHING COLD FRONT
ENCOUNTERING L-M60S SURFACE TDS IN MODERATELY UNSTABLE AIRMASS...AM
INCLINED TO LEAVE POPS AS IS AND NOT DOWNGRADE GOING NOS...AS
NUMERICAL GUIDANCE IS STARTING TO SUGGEST.

AFTER FROPA WX PICTURE IS FAIRLY STRAIGHT-FORWARD WITH SURFACE HIGH
BUILDING OVERHEAD PROVIDING COOL/DRY WEEKEND. SUSPECT THAT
DEVELOPMENT OF NW FLOW ALOFT WL YIELD A FEW MORE CLOUDS THAN PERHAPS
MODELS ARE SUGGESTING INTO EXTENDED PTN OF FORECAST...BUT NOT ENOUGH
FOR ANY POP...AT LEAST TIL SURFACE HIGH SHIFTS EAST AND NEXT FRONT
COMES INTO PLAY TUE.

AVN BASED GUIDANCE CONTINUES WITH COOLER APPROACH TO POST COLD FRONTAL
TEMPS AND TYPICALLY HANDLES THAT SCENARIO BETTER THAN FWC...WHICH
HAS BEEN GOING FCST STRATEGY AND WELL CONTINUE.

.PAH...NONE.
DH

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-100-
107>112-114-111900-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE PADUCAH KY
1040 AM CDT FRI MAY 11 2001

THIS THUNDERSTORM OUTLOOK COVERS THE REGION OF SOUTHEAST MISSOURI...
SOUTHERN ILLINOIS...SOUTHWEST INDIANA...AND WESTERN KENTUCKY. IT IS
VALID UNTIL 600 AM SATURDAY.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE QUAD
STATE THIS AFTERNOON AND EVENING.

A COLD FRONT WILL APPROACH FROM THE NORTHWEST THIS AFTERNOON...AND
MOVE THROUGH THE REGION THIS EVENING. WHILE THERE MAY BE A FEW
STORMS THAT DEVELOP OUT AHEAD OF THE FRONT...MOST THUNDERSTORM
DEVELOPMENT WILL ACCOMPANY THE FRONT ITSELF. THEREFORE THE BEST
CHANCE FOR STORMS...INCLUDING SEVERE WEATHER...WILL BE BETWEEN
ROUGHLY 300 PM AND 1000 PM.

THE ENVIRONMENT THE FRONT ENCOUNTERS IS FORECAST TO BECOME
MODERATELY UNSTABLE. WINDS ALOFT SUGGEST STORM DEVELOPMENT WILL BE
PRIMARILY LINEAR...BUT ISOLATED STORMS MAY FORM ON BOUNDARIES
THAT ARE DEVOID OF A MAIN LINE ORGANIZATION. LONG-LIVED ROTATING
STORMS ARE NOT ANTICIPATED...ALTHOUGH THE POTENTIAL FOR AN ISOLATED
STORM OR TWO TO HAVE ROTATION...PARTICULARLY WITH NUMEROUS OUTFLOW
BOUNDARIES PRESENT...DOES EXIST. THE PRIMARY THREAT OF SEVERE
WEATHER WILL BE DAMAGING WIND AND HAIL.

FORECAST STORM MOTION IS NORTHEAST AT 25 TO 30 MPH. LINE MOVEMENT
WILL BE MORE TO THE EAST AT 15 TO 20 MPH.

SPOTTERS SHOULD MONITOR NOAA RADIO AND MAINTAIN ALERT STATUS IN CASE
THEIR ACTIVATION IS REQUESTED.

DH