DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 291950
SWODY1
SPC AC 291947

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT SAT SEP 29 2012

VALID 292000Z - 301200Z

...NO SVR TSTM AREAS FORECAST...

THE ONLY CHANGE TO THE OUTLOOK FOR THIS ISSUANCE IS TO EXTEND THE 5
PERCENT WIND DAMAGE AND 2 PERCENT TORNADO PROBABILITY AREAS FURTHER
WEST INTO SCNTRL TX. MESOANALYSIS SUGGESTS THE AIRMASS IS MODERATELY
UNSTABLE WITH MLCAPE VALUES ESTIMATED AROUND 1500 J/KG. ALTHOUGH THE
LOW-LEVEL SHEAR IS NOT THAT STRONG...DIRECTIONAL SHEAR IN THE
BOUNDARY LAYER AND LOW LCL HEIGHTS COULD RESULT IN A MARGINAL SEVERE
THREAT FOR A FEW MORE HOURS.

..BROYLES.. 09/29/2012

.PREV DISCUSSION... /ISSUED 1105 AM CDT SAT SEP 29 2012/

...SYNOPSIS...
THE NERN CONUS TROUGH/GREAT LAKES UPPER LOW WILL SHIFT SE TODAY. AN
EMBEDDED SEWD ADVANCING IMPULSE ROUNDING THE BASE OF THIS TROUGH WAS
EVIDENT ON MORNING WV IMAGERY OVER THE MID OH VALLEY. A
SECOND...MORE SUBTLE IMPULSE WAS INDICATED BY 12Z MODEL GUIDANCE AND
SUGGESTED BY EARLY MORNING SHOWERS AND THUNDERSTORMS ACROSS NRN GA
AND FAR WRN NC. TOGETHER...THESE IMPULSES WILL TRACK ACROSS THE
CAROLINAS/MID ATLANTIC REGION THIS AFTERNOON AND EVENING...RESULTING
IN THE E/SE ADVANCEMENT OF A COLD FRONT EXTENDING ACROSS SRN NC INTO
NRN GA/SC. FURTHER WEST...THE SHORTWAVE TROUGH OVER W TX WILL BECOME
BETTER DEFINED AS IT TRACKS TOWARD ERN TX. THE ASSOCIATED SFC LOW
WILL MOVE IN TANDEM WITH THE SHORTWAVE TROUGH...BECOMING POSITIONED
NEAR THE UPPER TX COAST/SABINE RIVER VALLEY BY 12Z SUN.

...WRN GULF COAST REGION...
ABUNDANT CLOUD COVER AND ONGOING PRECIPITATION ACROSS THE REGION
WILL LIMIT DAYTIME HEATING. THE RESULTING POOR LAPSE RATES WILL CURB
AFTERNOON DESTABILIZATION TO AROUND 1000 J/KG MUCAPE DESPITE A VERY
MOIST AIRMASS /LOWER 70S DEWPOINTS...PW VALUES GREATER THAN 2
INCHES/. GIVEN THIS MOIST AIRMASS...AN ISOLATED STRONG/SVR DOWNBURST
MAY BE POSSIBLE IN STRONGER CELLS. THE THREAT FOR ISOLATED STRONG
WINDS AND POSSIBLY A TORNADO MAY INCREASE SOMEWHAT THIS
EVENING/OVERNIGHT AS ANOTHER MCS DEVELOPS IN RESPONSE TO THE
ORGANIZATION OF THE UPPER TROUGH AND EWD ADVANCEMENT OF SFC LOW.
SLIGHTLY INCREASING/BACKED LOW LEVEL FLOW WILL CONTINUE TO SUPPORT
AT LEAST A LOW SVR THREAT IN THIS ENVIRONMENT.

...CAROLINAS/FAR ERN GA...
CLOUD COVER ACROSS NC WILL LIMIT HEATING/DESTABILIZATION TODAY AND
THUS STORM INTENSITY AS MUCAPE VALUES STRUGGLE TO EXCEED 500-750
J/KG AND LAPSE RATES REMAIN POOR. HOWEVER...STRONGER DEEP LAYER FLOW
/30-40 KT BULK SHEAR/...A MOIST AIRMASS /MID TO UPPER 60S
DEWPOINTS...PW NEAR 1.50 INCHES/ AND INCREASING FORCING FOR ASCENT
WITH APPROACH OF SHORTWAVE IMPULSES MAY LEAD TO SOME WEAKLY
ORGANIZED STORM CLUSTERS CAPABLE OF PRODUCING A FEW STRONG/SVR WIND
GUSTS THROUGH THIS EVENING. FURTHER SOUTH TOWARD SE SC AND ERN
GA...THINNER CLOUD COVER WILL RESULT IN SOMEWHAT GREATER
HEATING/DESTABILIZATION AND BETTER LOW LEVEL LAPSE RATES. THIS
ENVIRONMENT MAY BE BETTER SUITED TO AN ISOLATED SVR WIND THREAT THIS
AFTERNOON AS ISO-SCT STORMS DEVELOP.

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