DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 180636
SWODY2
SPC AC 180634

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1234 AM CST TUE DEC 18 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM EXTREME NERN TX INTO THE
LOWER MS VALLEY REGION...

...SYNOPSIS...

MODEL SOLUTIONS REMAIN SIMILAR REGARDING SPEED AND AMPLITUDE OF THE
NEXT SIGNIFICANT UPPER TROUGH FORECAST TO AMPLIFY ACROSS THE SWRN
STATES TUESDAY. THIS FEATURE WILL ADVANCE RAPIDLY EWD INTO THE SRN
AND CNTRL PLAINS WEDNESDAY AND LOWER MS VALLEY WEDNESDAY NIGHT. A
DEEP CYCLONE WILL DEVELOP IN THE LEE OF ROCKIES AS EXIT REGION OF
UPPER JET ROTATES THROUGH BASE OF THE TROUGH AND INTO THE SRN HIGH
PLAINS. THIS LOW WILL TRACK NEWD THROUGH THE MID MS VALLEY WEDNESDAY
NIGHT. SEWD MOVING POLAR FRONT WILL OVERTAKE THE PACIFIC FRONT AND
SWEEP ACROSS THE SRN PLAINS AND MID-LOWER MS VALLEY. THIS BOUNDARY
WILL LIKELY EXTEND FROM THE SFC LOW OVER IL SWWD INTO MS/LA BY THE
END OF THIS PERIOD.

...EXTREME ERN OK...NERN TX THROUGH LOWER MS VALLEY REGION...

IT STILL APPEARS THE LIMITING FACTOR FOR A MORE ROBUST SEVERE EVENT
WITH THIS SYSTEM WILL BE VERY WEAK INSTABILITY. RECENT COLD FRONTAL
INTRUSION WILL SHUNT RICHER LOW LEVEL MOISTURE AT LEAST AS FAR SOUTH
AS THE CNTRL GULF. HOWEVER...SLY BOUNDARY LAYER WINDS WILL INCREASE
OVER THE WRN GULF LATER TUESDAY IN RESPONSE TO DEVELOPING LEE
CYCLONE. PARTIALLY MODIFIED GULF AIR WILL ADVECT THROUGH ERN TX AND
THE LOWER MS VALLEY TUESDAY NIGHT INTO WEDNESDAY WITH NEAR SFC
DEWPOINTS INCREASING TO AROUND 60 AS FAR NORTH AS ARKANSAS AND UPPER
60S NEAR THE TX/LA COASTS. SOME POTENTIAL ALSO EXISTS FOR LOW CLOUDS
TO DEVELOP ALONG THE AXIS OF MOISTURE RETURN...WHICH IN CONJUNCTION
WITH WEAK MID LEVEL LAPSE RATES WILL SIGNIFICANTLY LIMIT MUCAPE IN
PRE-FRONTAL WARM SECTOR DURING THE DAY.

LOW TOPPED CONVECTION IS EXPECTED TO FORM BY WEDNESDAY EVENING
WITHIN ZONE OF STRONG FRONTOGENETIC FORCING AND ALONG LEADING EDGE
OF DPVA ALOFT FROM NERN TX THROUGH ERN OK/WRN AR INTO SWRN MO.
DESTABILIZATION WILL REMAIN CONFINED TO A NARROW CORRIDOR IN
VICINITY OF THE PROGRESSIVE FRONT AS DEEPER MESOSCALE ASCENT
OVERTAKES THE MOIST AXIS. MUCH OF THE CONVECTION WILL PROBABLY
PRODUCE LIMITED LIGHTNING DUE TO ITS LOW TOPPED NATURE WITH EL
TEMPERATURES AOA -20C. NEVERTHELESS THE EVOLVING SQUALL LINE WILL BE
EMBEDDED WITHIN STRONG DEEP LAYER WINDS WITH LLJ STRENGTHENING TO
AOA 60 KT. LEWP AND BOWING SEGMENTS CAPABLE OF TRANSFERRING HIGHER
MOMENTUM AIR WITH STRONG TO DAMAGING GUSTS TO THE SFC WILL BE THE
MAIN THREAT AS ACTIVITY ADVANCES THROUGH THE LOWER MS VALLEY
OVERNIGHT.

..DIAL.. 12/18/2012

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