DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 140830
SWODY3
SPC AC 140828

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CST FRI DEC 14 2012

VALID 161200Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

A PROGRESSIVE SYNOPTIC PATTERN WILL PERSIST THROUGH SUNDAY WITH A
SERIES OF LOW AMPLITUDE SHORTWAVE TROUGHS MOVING THROUGH THE U.S.
ONE SUCH FEATURE WILL DEAMPLIFY AS IT CONTINUES THROUGH THE OH
VALLEY DURING THE DAY. FARTHER UPSTREAM ANOTHER TROUGH WILL MOVE
THROUGH THE SRN PLAINS...REACHING THE LOWER MS VALLEY LATER SUNDAY
NIGHT.

A COLD FRONT THAT SHOULD STRETCH FROM A WEAK SFC LOW OVER THE GREAT
LAKES SUNDAY MORNING WILL ADVANCE SEWD...LIKELY EXTENDING FROM THE
LOWER GREAT LAKES SWWD INTO NRN TX BY THE END OF PERIOD. A PACIFIC
FRONT SHOULD EXTEND FROM THE UPPER GREAT LAKES SWWD THROUGH ERN TX
SUNDAY MORNING AND SUBSEQUENTLY ADVANCE THROUGH THE OH...TN AND
LOWER MS VALLEY REGIONS.

...SERN STATES...

PERSISTENT SLY FLOW WILL MAINTAIN INFLUX OF MODIFIED CP AIR THROUGH
THE SERN U.S. WITH NEAR SFC DEWPOINTS RANGING FROM MID 60S NEAR THE
GULF COAST TO 50S OVER THE TN VALLEY. GIVEN THE LIMITED NWD EXTENT
OF THE RICHER LOW LEVEL MOISTURE AND POOR LAPSE RATES...INSTABILITY
WILL LIKELY REMAIN MARGINAL WITH MLCAPE AOB 500 J/KG. POTENTIAL WILL
EXIST FOR CONVECTION TO PERSIST ALONG CONVEYOR BELT AND WITHIN LOW
LEVEL CONFLUENT FLOW REGIME FROM LOWER MS THROUGH TN VALLEYS. WHERE
DIABATIC WARMING OCCURS...STORMS MAY BECOME SFC BASED DURING THE
AFTERNOON AND EVENING. WHILE LOW LEVEL WINDS ARE FORECAST TO REMAIN
VEERED TO SWLY DURING THE DAY...THIS REGION WILL REMAIN EMBEDDED
WITHIN STRONG FLOW ALOFT WITH WINDS INCREASING TO 60+ KT AT 500 MB
AND STRONG 0-6 KM SHEAR. CONVECTION MAY UNDERGO SOME INCREASE WITH
THE APPROACH OF THE SRN STREAM WAVE AND POSSIBLE STRENGTHENING LLJ
SUNDAY NIGHT. GIVEN THE POTENTIAL FOR NEAR SFC BASED STORMS AND
STRONG DEEP SHEAR...A FEW STORMS MIGHT DEVELOP SUPERCELL STRUCTURES
AND POSE A SEVERE THREAT. HOWEVER...LIKELIHOOD OF LIMITED
INSTABILITY PRECLUDES INTRODUCTION OF MORE THAN 5% SEVERE
PROBABILITIES AT THIS TIME.

...OH VALLEY...

DESPITE MORE LIMITED MOISTURE RETURN WITH ONLY 40S DEWPOINTS
EXPECTED...COLD AIR ALOFT /-20 C AT 500/ AND DIABATIC HEATING MAY
CONTRIBUTE TO AT LEAST WEAK SFC BASED INSTABILITY DURING THE
AFTERNOON. LOW TOPPED CONVECTION WILL BE POSSIBLE AHEAD OF THE FRONT
WITHIN A STRONGLY SHEARED ENVIRONMENT WITH THE APPROACH OF THE LOW
AMPLITUDE SHORTWAVE TROUGH. SOME OF THIS ACTIVITY MIGHT BECOME
CAPABLE OF PRODUCING ISOLATED STRONG WIND GUSTS...BUT LIMITED
INSTABILITY PRECLUDES INTRODUCTION OF MORE THAN 5% SEVERE
PROBABILITIES AT THIS TIME.

..DIAL.. 12/14/2012

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