Severe Thunderstorm Warning 121, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
318 PM CDT FRI JUN 4 1999

MAIN FCST PROBLEM: TEMPS AND PCPN...IF ANY...

ALL MODELS INITIALIZED SIMILARLY THIS MORNING WITH RESPECT TO
1200Z WV IMAGE. MODELS DIFFER MAINLY IN TIMING OF EJECTING DEEP
500MB TROF NEWD AS AN OPEN WAVE. ETA SLOWEST WITH THE SHRT WV
WHILE NGM THE FASTEST...AVN VERY CLOSE TO ETA SOLN. WILL GIVE
THE NOD TO THE SLOWER ETA/AVN SOLNS SINCE DEEP LOW WILL PROBLY
BE SLOW TO MOVE OUT INITIALLY.

ANYWAY ALL MODELS AGREE WITH BUILDING 500MB HTS ACROSS MO DURG THE
NEXT 24 TO 36 HRS. THIS WILL LEAD TO STRENGTHENING MID-LEVEL CAP AND
SUPPRESSING TSTM DVLPMNT THRU SUN AM.

LATEST SFC ANALYSIS HAD WARM FNT WELL TO THE NORTH OF THE CWA.
OUTFLOW FROM TSTM COMPLEX OVER IA HAD PUSHED INTO NORTHERN MO. DWPTS
IN THE LOWER 70S QUITE COMMON THRU THE AREA WITH TEMPS IN THE MID TO
UPPER 80S. THE AIRMASS WAS UNSTABLE BUT DESPITE THIS...A CAP AROUND
850MBS WAS PREVENTING CONVCTN FROM FIRING OVER THE AREA...WITH THE
EXCEPTION OF SOME CU. AFTN TEMPS WOULD HAVE TO REACH AT LEAST 92 DEG
BEFORE LFC REACHED. THE EXECPTION IS OVER THE EXTREME NRN COUNTIES OF
MORGAN...MILLER...AND MARIES. WILL PUT IN A 20 PCT POP FOR THOSE
COUNTIES. THIS IS DUE TO THE PSSBLTY OF OUTFLOW BOUNDARY BEING KICKED
SWD FROM TSTM COMPLEX ACROSS NERN MO. OUTFLOW BOUNDARY WOULD ADD
THE IMPETUS TO BREAKING CAP...IF THIS BOUNDARY OCCURS.

OTHERWISE WX CONDITIONS WILL BE SUMMERLIKE FOR THIS WEEKEND WITH
TEMPS IN THE UPPER 80S TO LOWER 90S AND LOWS NR 70. THE DEEP UPPER
LOW WILL BE KICKED NEWD TO THE NRN PLNS SAT NGT AND SUN. 500 HTS WILL
FALL SOMEWHAT ON SUNDAY BUT BELIEVE THAT CAP WILL BE TOO STG TO ALLOW
TSTM OVER THE WRN PTN OF CWA SAT NGT THRU SUN AM.

UPPER JET ASSOC WITH EJECTED 500MB SHRT WV WILL BE CNTRD OVER THE NRN
PLNS ON SUN...WITH RR QUAD OF JET AFFECTING SWRN MO. THIS WILL
PROVIDE A SOURCE FOR MID-LEVEL LIFT. 500HTS WILL CONT TO FALL BY SUN
EVE...IMPLYING SOME COOLING ALOFT AND AN EROSION OF CAP. SINCE SFC
BASED INSTAB WILL EXIST...THERE IS THE POSSIBILITY FOR TSTMS TO DVLP
LATE SUN AFTN OR SUN EVE. THE QUESTION IS...WILL THE CAP HOLD OR
NOT? WILL OPT TO LEAVE MENTION OF PCPN OUT OF THE FCST FOR SUN BUT
WILL MENTION FOR SUN NGT IN XTNDED FCST.

WENT A FEW DEGREES WARMER ON FWC AND FAN GUID ON TEMPS.

CCF
SGF UU 069/089 070/088 066 12-00-
JLN UU 070/092 070/089 068 12-00-

D.STEINMETZ

ILZ058>060-064-065-069-070-074-079-095>102-MOZ009-010-018-019-026-
027-034>036-041-042-047>052-059>065-072>075-084-085-099-042200-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
145 PM CDT FRI JUN 4 1999

THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON...ESPECIALLY
OVER NORTHEAST MISSOURI AND WEST CENTRAL ILLINOIS.  DUE TO THE VERY
WARM AND HUMID AIR FUELING THESE STORMS...HAIL AND HIGH WINDS
MAY OCCUR WITH SOME OF THE STRONGER STORMS.

SPOTTER ACTIVATION MAY BECOME NECESSARY...SO STORM SPOTTER GROUPS
AND EMERGENCY MANAGERS ARE URGED TO MONITOR WEATHER DEVELOPMENTS.

THIS OUTLOOK COVERS THE COUNTY WARNING AREA OF THE NATIONAL WEATHER
SERVICE FORECAST OFFICE IN ST LOUIS.  ARE$AS INCLUDED ARE PORTIONS OF
NORTHEAST...CENTRAL...EAST CENTRAL AND SOUTHEAST MISSOURI AS WELL AS
WEST CENTRAL AND SOUTHWEST ILLINOIS.

TRUETT

ILZ058>060-064-065-069-070-074-079-095>102-MOZ009-010-018-019-026-
027-034>036-041-042-047>052-059>065-072>075-084-085-099-042200-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
255 PM CDT FRI JUN 4 1999

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE REST
OF THIS AFTERNOON AND EVENING OVER PARTS OF NORTHEAST AND
EAST CENTRAL MISSOURI...AND ADJACENT AREAS OF WESTERN ILLINOIS.
THIS SLIGHT RISK AREA IS GENERALLY ALONG AND EAST OF A
KIRKSVILLE...FULTON MISSOURI LINE.

THUNDERSTORMS WILL MOVE THROUGH NORTHEAST MISSOURI AND WEST
CENTRAL ILLINOIS THIS AFTERNOON...AND MAY PUSH INTO EAST CENTRAL
MISSOURI AND PARTS OF SOUTHWEST ILLINOIS EARLY THIS EVENING.
DUE TO THE VERY WARM AND HUMID AIR FUELING THESE STORMS...HAIL
AND HIGH WINDS MAY OCCUR WITH SOME OF THE STRONGER STORMS.

A SEVERE THUNDERSTORM WATCH HAS ALREADY BEEN POSTED FOR NORTHEAST
MISSOURI AND WEST CENTRAL ILLINOIS UNTIL 7 PM.  STORM SPOTTER GROUPS
IN EAST CENTRAL MISSOURI AND SOUTHWEST ILLINOIS SHOULD REMAIN ALERT
FOR POSSIBLE SKYWARN ACTIVATION LATER THIS AFTERNOON OR EARLY THIS
EVENING.

THIS OUTLOOK COVERS THE COUNTY WARNING AREA OF THE NATIONAL WEATHER
SERVICE FORECAST OFFICE IN ST LOUIS.  AREAS INCLUDED ARE PORTIONS OF
NORTHEAST...CENTRAL...EAST CENTRAL AND SOUTHEAST MISSOURI AS WELL AS
WEST CENTRAL AND SOUTHWEST ILLINOIS.

TRUETT