SWODY1
SPC AC 212000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE JUL 21 2009
VALID 212000Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS LOWER MS VALLEY TO
S-CENTRAL TX...
--- UPDATES ---
...W-CENTRAL GULF COAST REGION...
MRGL SVR WIND PROBABILITIES HAVE BEEN EXPANDED EWD ACROSS THIS
REGION. SFC WARM FRONTAL ZONE CONTINUES TO LIFT NEWD ACROSS NRN MS
AND WRN/SRN AL...DEFINED WELL DIURNALLY BY MOISTURE FIELD GIVEN STG
INSOLATION ON BOTH SIDES OF FRONT AND HEATING OF DRIER AIR TO ITS N.
BKN BANDS OF PREFRONTAL TSTMS WILL CONTINUE TO POSE THREAT FOR GUSTS
NEAR SVR LEVELS AND ISOLATED DAMAGING DOWNBURSTS AS IT MOVES EWD
ACROSS DELTA REGION AND SRN LA...INTO POST WARM-FRONTAL ENVIRONMENT
CHARACTERIZED BY SFC DEW POINTS UPPER 60S TO LOW 70S F AND STG SFC
HEATING. WEAK KINEMATIC FIELDS...INCLUDING LACK OF EITHER LOW-LEVEL
OR DEEP-LAYER SHEAR...WILL LIMIT STORM ORGANIZATION TO
MULTICELLULAR/LINEAR S AND SE OF CATEGORICAL SLGT RISK OUTLOOK.
..EDWARDS.. 07/21/2009
.PREV DISCUSSION... /ISSUED 1110 AM CDT TUE JUL 21 2009/
...LOWER MISSISSIPPI VALLEY...
WELL DEFINED MCV EVOLVED OUT OF LAST NIGHTS SEVERE CONVECTION OVER
THE CENTRAL PLAINS AND THIS MORNING IS MOVING SLOWLY EWD ALONG THE
AR/MO BORDER REGION. CIRCULATION CENTER EXPECTED TO BE VICINITY MO
BOOTHEEL BY THIS EVENING. A BROAD AREA OF NON-SEVERE CONVECTION IS
SPREADING EWD ACROSS AR INTO NERN TX.
COLD FRONT THAT IS ACCOMPANYING THE LARGE SCALE TROUGH THAT IS STILL
EVOLVING OVER THE UPPER MS VALLEY CURRENTLY EXTENDS FROM WRN MO
WSWWD ACROSS CENTRAL OK TO SRN TX PANHANDLE.
AIR MASS IN THE WAKE OF AR CONVECTION AND AHEAD OF COLD FRONT
REMAINS VERY MOIST WITH DEWPOINTS INTO THE LOW 70S. THE AT LEAST
TEMPORARY CLEARING OBSERVED ALONG RED RIVER WILL ALLOW SUFFICIENT
HEATING TO DEVELOP MLCAPES AOA 2500 J/KG WITH LITTLE CINH BY EARLY
THIS AFTERNOON.
MID LEVEL WINDS HAVE BEEN ENHANCED BY THE MCV CIRCULATION AND WILL
PROVIDE SHEAR PROFILES SUFFICIENT FOR SEVERE STORMS AND POSSIBLE
SUPERCELLS ALONG AND AHEAD OF COLD FRONT BY MID AFTERNOON. PRIMARY
THREAT WILL BE DAMAGING WINDS WITH STRONGEST STORMS INCLUDING
SUPERCELLS. THERE IS A THREAT FOR ISOLATED TORNADOES GIVEN THE
FAVORABLE LOW LEVEL VEERING SHEAR PROFILES...INSTABILITY AND LOW
LFC/S.
FURTHER E AHEAD OF MCV AND ASSOCIATED WITH THE CURRENT BAND OF
CONVECTION THERE IS A THREAT OF ISOLATED SEVERE STORMS DEVELOPING
ACROSS MS RIVER...HOWEVER EXTENSIVE CLOUD COVER AND GENERALLY LESS
FAVORABLE INSTABILITY SHOULD KEEP THE THREAT LOW.
...SRN HIGH PLAINS...
THE SURFACE FRONT TRAILS WESTWARD INTO WEST TX AND EASTERN NM.
STRONG HEATING THIS AFTERNOON WILL LIKELY RESULT IN SCATTERED
THUNDERSTORMS IN REGION OF WEAK UPSLOPE FLOW BEHIND THE BOUNDARY.
WEAK FLOW ALOFT WILL LIMIT CONVECTIVE ORGANIZATION...BUT STEEP LOW
AND MID LEVEL LAPSE RATES MAY RESULT IN GUSTY WINDS AND HAIL IN
STRONGER CELLS.
...UPPER MS VALLEY...
COLD POOL ASSOCIATED WITH LARGE SCALE TROUGH AND SURFACE HEATING IN
THE WAKE OF DEPARTING CLOUD SHIELD SHOULD LEAD TO SUFFICIENT
INSTABILITY FOR AFTERNOON CONVECTION. WHILE THE SHEAR PROFILES ARE
GENERALLY WEAK...THE COLD MID LEVEL AIR MASS AND STEEP LAPSE RATES
WILL SUPPORT HAIL IN STRONGER UPDRAFTS. MLCAPES AOA 1000 J/KG
SUGGESTS HAIL COULD BE SEVERE IN STRONGER STORMS.
...UPPER OH VALLEY...
WEAK UPPER LOW CONTINUES TO TRACK SLOWLY NORTHEASTWARD ACROSS
EASTERN OH/WESTERN PA. LARGE SCALE LIFT AHEAD OF THE LOW COUPLED
WITH MODERATE INSTABILITY MAY RESULT IN SCATTERED AFTERNOON
THUNDERSTORMS FROM NORTHERN VA INTO CENTRAL NY. RATHER COOL
TEMPERATURES ALOFT COULD POSE A THREAT OF HAIL AND GUSTY WINDS IN
STRONGEST CORES...BUT ORGANIZED SEVERE STORMS ARE NOT ANTICIPATED.
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