DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 170820
SWODY3
SPC AC 170818

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CST MON DEC 17 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN TX...EXTREME SERN OK
THROUGH THE LOWER MS VALLEY...

...SYNOPSIS...

MODELS HAVE CONVERGED ON SIMILAR SOLUTIONS REGARDING THE SPEED AND
AMPLITUDE OF THE NEXT SIGNIFICANT UPPER TROUGH FORECAST TO AMPLIFY
ACROSS THE SWRN STATES TUESDAY. THIS FEATURE WILL CONTINUE RAPIDLY
EWD THROUGH 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 REGIONS. 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...

PRIMARY LIMITING FACTOR FOR A MORE ROBUST SEVERE EVENT WITH THIS
SYSTEM WILL LIKELY BE VERY WEAK INSTABILITY. COLD FRONT THAT WILL
MOVE OFF THE TX AND LA COASTS MONDAY 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 MAY SIGNIFICANTLY LIMIT MUCAPE TO AOB 500 J/KG.

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 50 KT. LEWP AND BOWING SEGMENTS CAPABLE OF TRANSFERRING HIGHER
MOMENTUM AIR WITH STRONG TO DAMAGING GUSTS DOWN TO THE SFC WILL BE
THE MAIN THREAT AS ACTIVITY ADVANCES THROUGH THE LOWER MS VALLEY
OVERNIGHT.

HAVE SCALED BACK ON PROBABILITIES FROM DAY 4 WITH ONLY 15% SLIGHT
RISK CATEGORY AT THIS TIME DUE TO THE LIMITING CONSTRAINTS OF THE
EXPECTED MARGINAL THERMODYNAMIC ENVIRONMENT.

..DIAL.. 12/17/2012

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.