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MESOSCALE DISCUSSION 0489
NWS STORM PREDICTION CENTER NORMAN OK
0732 PM CDT THU MAR 27 2008
AREAS AFFECTED...NERN OK...NWRN AR...S CNTRL THROUGH E CNTRL MO AND
S CNTRL IL
CONCERNING...SEVERE THUNDERSTORM WATCH 138...139...
VALID 280032Z - 280200Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
138...139...CONTINUES.
THREAT FOR MAINLY LARGE HAIL WILL PERSIST INTO MUCH OF THE EVENING
FROM NERN OK...SRN THROUGH E CNTRL MO INTO S CNTRL IL. AN ISOLATED
TORNADO OR TWO REMAINS POSSIBLE WITH SURFACE BASED DISCRETE STORMS
FROM NERN OK THROUGH SRN MO NEXT HOUR OR TWO.
COLD FRONT EXTENDS FROM SRN IND THROUGH SRN IL TO JUST SOUTH OF ST
LOUIS THEN SWWD THROUGH SWRN MO...NERN AND SWRN OK. WARM SECTOR
SOUTH OF THIS BOUNDARY REMAINS MODERATELY UNSTABLE WITH MLCAPE FROM
1000 TO 1500 J/KG ALONG WITH STEEP LAPSE RATES. AS EVIDENCED ON THE
00Z RAOB FROM SPRINGFIELD...STRONG HEATING AND BOUNDARY LAYER MIXING
WEAKENED THE CAP ENOUGH FOR SURFACE BASED STORMS TO DEVELOP WITHIN
THE ZONE OF LOW LEVEL CONVERGENCE ALONG FRONT FROM NERN OK INTO E
CNTRL MO. LOW LEVEL HODOGRAPHS ARE SMALL OWING TO MODEST AND VEERED
LOW LEVEL WINDS. HOWEVER...EFFECTIVE BULK SHEAR OF 40 TO 50 KT HAS
SUPPORTED SUPERCELL STRUCTURES. THE MAIN THREAT WITH THESE STORMS IS
LARGE HAIL. ISOLATED BRIEF TORNADOES HAVE BEEN REPORTED OVER NERN OK
AND SRN MO. GIVEN THE RELATIVELY LARGE TEMPERATURE-DEWPOINT
SPREADS...SURFACE BASED INVERSION WILL BECOME MORE PRONOUNCED WITH
ONSET OF NOCTURNAL COOLING. THIS SUGGEST ANY REMAINING TORNADO
THREAT WILL GRADUALLY DECREASE IN THIS REGION. STORMS ARE SHOWING A
TENDENCY TO BACKBUILD DOWN THE FRONT IN ERN OK. HOWEVER...SRN EXTENT
OF DEVELOPMENT IN WARM SECTOR WILL BE LIMITED BY A STRENGTHENING
CAP...ESPECIALLY AS THE BOUNDARY LAYER COOLS.
SHORT TERM TORNADO THREAT APPEARS A LITTLE HIGHER WITH SUPERCELLS
ACROSS SERN MO NEXT HOUR OR TWO WHERE TEMPERATURE-DEWPOINT SPREADS
ARE LOWER AND 0-1 KM HODOGRAPHS ARE LARGER ON NOSE OF THE LOW LEVEL
JET.
..DIAL.. 03/28/2008
ATTN...WFO...LSX...LZK...SGF...TSA...
38499065 38038976 36089350 34919521 35699599 37199381
37859283 38349185
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