SPC AC 121200
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0700 AM CDT FRI JUN 12 2009
VALID 121300Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS INTO
THE CAROLINAS...
A FLAT RIDGE REMAINS OVER THE CENTRAL UNITED STATES TODAY...WITH
SEVERAL WEAK SHORTWAVE TROUGHS EMBEDDED IN THE MODERATELY FAST
WESTERLY FLOW FROM THE PLAINS TO THE EAST COAST. ONE SHORTWAVE
FEATURE IS CURRENTLY NOTED IN WATER VAPOR IMAGERY OVER EASTERN
CO/WESTERN KS AND WILL BE THE IMPETUS FOR SEVERE THUNDERSTORM
ACTIVITY FROM OK/KS INTO TN/MS/AL TODAY.
...OK/KS/MS/AR/TN/MS...
TWO LINES OF STRONG/SEVERE STORMS ARE ONGOING THIS MORNING OVER
CENTRAL KS AND NORTHERN OK. BOTH CLUSTERS APPEAR TO BE ASSOCIATED
WITH THE AFOREMENTIONED SHORTWAVE TROUGH...ALTHOUGH THE WESTERN
STORMS ARE MOVING FASTER THAN THE EASTERN LINE. IT APPEARS LIKELY
THAT THE ACTIVITY WILL MERGE LATER THIS MORNING OR EARLY AFTERNOON
AS THE PRIMARY UPPER FORCING OVERTAKES THE LEAD CONVECTION. THIS
SHOULD RESULT IN AN EASTWARD ACCELERATION OF THE STORMS ALONG THE
WEAK BAROCLINIC ZONE DRAPED ACROSS AR. AN EXTREMELY UNSTABLE
AIRMASS IS EXPECTED OVER PARTS OF OK/WESTERN AR WITH DEWPOINTS IN
THE 70S AND AFTERNOON MLCAPE VALUES OVER 4000 J/KG. EFFECTIVE SHEAR
AOA 60 KNOTS WILL ALSO MAINTAIN AN ORGANIZED RISK OF SEVERE STORMS
THROUGH THE AFTERNOON AND EVENING AS ACTIVITY SPREADS INTO PARTS OF
WESTERN TN/NORTHERN AL/NORTHERN MS. FORECAST SOUNDINGS SUGGEST
PARAMETERS FAVORABLE FOR VERY LARGE HAIL...SIGNIFICANT DAMAGING
WINDS...AND ISOLATED TORNADOES ACROSS THIS AREA. AN UPGRADE TO
MODERATE RISK MAY OCCUR LATER TODAY AS THE CORRIDOR OF GREATEST
THREAT BECOMES MORE CLEAR AND IF STORMS INTENSIFY AS CURRENTLY
EXPECTED.
...CAROLINAS/GA/AL...
FARTHER EAST...SCATTERED THUNDERSTORMS WILL FORM THIS AFTERNOON FROM
EAST TN/AL EASTWARD INTO THE CAROLINAS. SUFFICIENT VERTICAL SHEAR
WILL BE PRESENT FOR A FEW SEVERE STORMS...ALBEIT LESS ORGANIZED THAN
FARTHER WEST. LATE TONIGHT...SOME POTENTIAL EXISTS FOR LONG-LIVED
MCS MOVING INTO THIS REGION FROM THE WEST.
...OK/TX ALONG DRYLINE...
AN EXTREMELY UNSTABLE AIRMASS IS EXPECTED TO DEVELOP THIS AFTERNOON
ALONG AND EAST OF THE SURFACE DRYLINE ACROSS CENTRAL/EASTERN OK AND
NORTH CENTRAL TX. FORECAST SOUNDINGS SUGGEST A WEAK CAPPING
INVERSION WILL SUPPRESS CONVECTION FOR MOST OF THE DAY.
HOWEVER...ENHANCED CONVERGENCE ALONG THE REMNANT OUTFLOW BOUNDARY
FROM THIS MORNINGS STORMS ACROSS NORTHERN OK MAY HELP TO INITIATE
ISOLATED STORMS. ALSO...MOST MODELS SHOW ISOLATED CELLS FORMING
DURING THE HEAT OF THE DAY OVER NORTH CENTRAL AND NORTHEAST TX. ANY
STORM THAT FORMS IN THIS ENVIRONMENT WILL HAVE A CONDITIONAL RISK OF
BECOMING A SUPERCELL AND WILL POSE A RISK OF LARGE HAIL AND DAMAGING
WINDS.
..HART/JEWELL.. 06/12/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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