DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 140646
SWODY2
SPC AC 140645

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CST FRI DEC 14 2012

VALID 151200Z - 161200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

UPPER TROUGH OVER CA WILL EJECT INTO THE SRN PLAINS BY LATE FRIDAY
AFTERNOON. THIS FEATURE WILL DEAMPLIFY AS IT CONTINUES THROUGH THE
MID MS AND OH VALLEYS SATURDAY AND THE LOWER GREAT LAKES SATURDAY
NIGHT. SHORTWAVE TROUGH NOW APPROACHING THE PACIFIC NW WILL FOLLOW
CLOSELY ON THE HEELS OF THE LEAD TROUGH...REACHING THE SRN PLAINS
SATURDAY AFTERNOON AND LOWER MS VALLEY SATURDAY NIGHT.

AT THE SFC AN AREA OF LOW PRESSURE IS FORECAST TO WEAKEN AS IT MOVES
FROM THE MID MS VALLEY TO GREAT LAKES IN ASSOCIATION WITH
DEAMPLIFYING LEAD SHORTWAVE TROUGH. COLD FRONT WILL ADVANCE SEWD AND
EXTEND FROM THE SFC LOW OVER THE GREAT LAKES SWWD INTO OK BY THE END
OF THE PERIOD. FARTHER SOUTH...DRYLINE OR PACIFIC FRONT WILL MOVE
THROUGH ERN TX.

...ERN TX THROUGH LOWER MS...TN AND OH VALLEY REGIONS...

PRIMARY LIMITING FACTOR FOR A MORE ROBUST SEVERE WEATHER THREAT WILL
LIKELY BE QUALITY OF GULF MOISTURE RETURN AND INSTABILITY AHEAD OF
THE LEAD SHORTWAVE TROUGH THAT WILL BE LOCATED OVER THE MID MS
VALLEY EARLY SATURDAY. TRAJECTORIES EMANATING FROM CP HIGH PRESSURE
OVER THE ERN U.S. ARE CONTRIBUTING TO WRN GULF SFC DEWPOINTS IN THE
50S. AS THIS RIDGE AXIS SHIFTS EWD AND A LEE LOW BECOMES ESTABLISHED
OVER THE CNTRL/SRN PLAINS...WRN GULF TRAJECTORIES WILL BECOME MORE
SLY AND RICHER MOISTURE WILL BEGIN RETURNING THROUGH SERN TX AND THE
LOWER MS VALLEY. SFC DEWPOINTS SHOULD INCREASE TO UPPER MID TO UPPER
60S ACROSS SERN TX INTO LA...BUT WITH 50S FARTHER NORTH INTO THE TN
AND OH VALLEYS.

PRIMARY /50+ KT/ LLJ WILL DEVELOP NEWD THROUGH THE LOWER-MID MS...TN
AND OH VALLEYS IN ASSOCIATION WITH THE LEAD SHORTWAVE TROUGH. THIS
WILL LEAVE SOMEWHAT WEAKER AND VEERED LOW LEVEL FLOW FARTHER SW
ACROSS ERN TX. ZONE OF MOSTLY ELEVATED CONVECTION MAY BE ONGOING
EARLY SATURDAY ALONG WARM CONVEYOR BELT FROM ERN TX INTO THE LOWER
MS VALLEY...GRADUALLY SHIFTING EWD. TENDENCY WILL BE FOR STRONGER
FORCING TO LIFT NEWD THROUGH THE OH VALLEY DURING THE DAY WHERE
INSTABILITY AND MOISTURE RETURN WILL BE LIMITED.

SOME THREAT FOR SEVERE STORMS MAY INCREASE PRIMARILY SATURDAY NIGHT
FROM THE LOWER MS INTO THE TN VALLEY. CONTINUED INFLUX OF BOUNDARY
LAYER MOISTURE...APPROACH OF SRN STREAM SHORTWAVE TROUGH AND
SUBTROPICAL UPPER JET MIGHT BE SUFFICIENT TO REINVIGORATE CONVECTION
ALONG THE CONVEYOR BELT WHERE LARGE HODOGRAPHS AND STRONG DEEP SHEAR
WILL EXIST. HOWEVER...CURRENT INDICATIONS ARE THAT STORMS WILL
PROBABLY REMAIN SLIGHTLY ELEVATED WITHIN A WEAK INSTABILITY
ENVIRONMENT WHICH MAY ULTIMATELY SERVE AS LIMITING FACTORS.

..DIAL.. 12/14/2012

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