SPC AC 261228
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0728 AM CDT SAT SEP 26 2009
VALID 261300Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER OH
VALLEY...
THE LARGE UPPER LOW THAT HAS BEEN PERSISTENT ACROSS THE CENTRAL
PLAINS FOR THE PAST FEW DAYS IS BECOMING PROGRESSIVE AND WILL TRACK
EASTWARD INTO THE OH VALLEY BY TONIGHT. RATHER LARGE MID LEVEL
HEIGHT FALLS AND STRENGTHENING WINDS ALOFT WILL OCCUR FROM THE MID
MS VALLEY INTO THE SOUTHEAST STATES. THIS IS LIKELY TO ENHANCE THE
RISK OF ISOLATED STRONG/SEVERE STORMS THIS AFTERNOON AND EVENING.
...LOWER OH VALLEY...
WATER VAPOR IMAGERY SHOWS A COMPACT VORT LOBE ROTATING AROUND UPPER
LOW INTO MO/AR. THIS FEATURE WILL MOVE INTO SOUTHERN IL/WESTERN KY
BY EARLY AFTERNOON...WHERE SOME SURFACE HEATING AND DEWPOINTS IN THE
60S WILL YIELD MLCAPE VALUES AROUND 500 J/KG. COOLING TEMPERATURES
ALOFT MAY FURTHER DESTABILIZE THE REGION THROUGH THE AFTERNOON AS
SCATTERED THUNDERSTORMS DEVELOP ALONG/AHEAD OF THE APPROACHING
SURFACE FRONT. WESTERLY MID LEVEL WINDS ARE FORECAST TO BECOME
RATHER STRONG DURING THE AFTERNOON...PROMOTING CONVECTIVE
ORGANIZATION WITH ISOLATED SEVERE STORMS POSSIBLE. HAIL AND
DAMAGING WINDS APPEAR TO BE THE MAIN THREATS.
...AL/GA...
MORNING SURFACE ANALYSIS SHOWS A WEDGE FRONT MOVING SLOWLY
SOUTHWESTWARD ACROSS NORTH GA INTO EASTERN AL. THE AIRMASS WEST OF
THE WEDGE FRONT REMAINS VERY MOIST AND MARGINALLY UNSTABLE WITH
DEWPOINTS IN THE 70S AND PWAT VALUES OVER 2 INCHES PER 12Z RAOBS.
SCATTERED THUNDERSTORMS HAVE ALREADY BEGUN TO FORM OVER PARTS OF
MS/AL/TN...AND SHOULD CONTINUE TO PROGRESS EASTWARD THROUGH THE DAY.
ENHANCED LOW LEVEL CONVERGENCE AND SHEAR IN VICINITY OF THE WEDGE
FRONT OVER EASTERN AL AND NORTH GA MAY RESULT IN ISOLATED STRONG
STORMS CAPABLE OF GUSTY/DAMAGING WINDS.
...EASTERN NC...
MODELS CONTINUE TO SHOW RAPID CYCLOGENESIS ALONG THE NC COAST LATER
TONIGHT. IF THIS LOW CAN TRACK ONSHORE...ENHANCED LOW LEVEL
VERTICAL SHEAR AND INSTABILITY IN WARM SECTOR WOULD SUPPORT A RISK
OF SUPERCELLS CAPABLE OF GUSTY/DAMAGING WINDS AND/OR AN ISOLATED
TORNADO.
..HART/GRAMS.. 09/26/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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