SWODY2
SPC AC 131729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CST TUE NOV 13 2007
VALID 141200Z - 151200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER MS
VALLEY AND WRN PARTS OF THE TN VALLEY...
..SYNOPSIS...
LOW AMPLITUDE UPPER TROUGH NOW OVER MT IS FORECAST TO AMPLIFY OVER
THE MS VALLEY AND GREAT LAKES REGION WEDNESDAY AS STRONG LOW LEVEL
COLD ADVECTION ATTENDING CP HIGH PRESSURE BUILDS SEWD THROUGH THE
PLAINS IN WAKE OF SEWD ADVANCING COLD FRONT. EARLY WEDNESDAY THE
FRONT IS FORECAST TO EXTEND FROM A SURFACE LOW IN ERN ONTARIO SWWD
THROUGH THE GREAT LAKES...SRN MO AND THE SRN PLAINS. THIS BOUNDARY
WILL ADVANCE SEWD DURING THE DAY...AND BY WEDNESDAY EVENING SHOULD
EXTEND FROM THE NERN STATES THROUGH THE TN AND LOWER MS VALLEYS INTO
SRN TX.
..LOWER MS VALLEY AND WRN TN VALLEY AREAS...
PERSISTENT SWLY BOUNDARY LAYER FLOW IN PRE-FRONTAL WARM SECTOR WILL
CONTRIBUTE TO NEWD ADVECTION OF MID TO UPPER 60S DEWPOINTS FARTHER
NEWD INTO THE LOWER MS AND TN VALLEY AREAS WEDNESDAY. SURFACE
HEATING WILL CONTRIBUTE TO FURTHER DESTABILIZATION. MODEST 6-6.5
C/KM MID LEVEL LAPSE RATES WILL LIMIT OVERALL DEGREE OF INSTABILITY
WITH AN AXIS OF MLCAPE AROUND 1000 J/KG OVER PARTS OF AR AND NRN LA
TO AOB 500 J/KG FARTHER NEWD INTO THE TN VALLEY REGIONS. STORMS ARE
EXPECTED TO REDEVELOP BY EARLY AFTERNOON FROM PARTS OF AR INTO TN
WITHIN ZONE OF FRONTAL FORCING AND HEIGHT FALLS. STRENGTHENING
HEIGHT GRADIENT ASSOCIATED WITH THE AMPLIFYING UPPER TROUGH WILL
RESULT IN INCREASING MID-UPPER FLOW OVER THE TN AND LOWER MS VALLEY
REGIONS. POSITIVE TILT NATURE OF THE UPPER TROUGH AND LACK OF
CYCLOGENESIS ALONG SERN U.S. PORTION OF THE FRONT WILL CONTRIBUTE TO
UNIDIRECTIONAL WLY WIND PROFILES. THE STRONGEST DEEP SHEAR WILL
LIKELY REMAIN POST FRONTAL. HOWEVER...0-6 KM SHEAR OF 35 TO 40 KT IN
VICINITY OF FRONT WILL BE SUFFICIENT FOR SOME ORGANIZED STORM
STRUCTURES. STORMS ARE EXPECTED TO DEVELOP ALONG FRONT FROM THE TN
VALLEY SWWD INTO THE LOWER MS VALLEY AS THE BOUNDARY LAYER
DESTABILIZES DURING THE DAY. PRIMARY STORM MODE IS EXPECTED TO
EVOLVE INTO LINES. HOWEVER...VERTICAL WIND PROFILES MAY BE
SUFFICIENT FOR SOME UPDRAFTS TO DEVELOP ROTATION...ESPECIALLY OVER
PARTS OF THE LOWER MS VALLEY WHERE THERE APPEARS TO BE A SLIGHTLY
BETTER CHANCE OF MAINTAINING SOME DISCRETE OR MIXED STORM MODES.
EXPECTED MODEST THERMODYNAMIC ENVIRONMENT COULD SERVE AS AN OVERALL
LIMITING FACTOR. HOWEVER...ISOLATED STRONG TO DAMAGING WIND GUSTS
AND HAIL WILL BE POSSIBLE WITH THE STRONGER STORMS. SEVERE THREAT
SHOULD GRADUALLY DECREASE AFTER SUNSET AS THE BOUNDARY LAYER
STABILIZES.
.DIAL.. 11/13/2007
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