SWODY1
SPC AC 191630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT MON MAR 19 2012
VALID 191630Z - 201200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON THROUGH TONIGHT
FOR EXTREME WRN AR...SE OK...AND CENTRAL/NE TX...
...THERE IS A SLGT RISK OF SVR TSTMS FROM S CENTRAL TX TO MO AND ERN
DAKOTAS/WRN MN THROUGH TONIGHT...
...SYNOPSIS...
A HIGHLY AMPLIFIED PATTERN PERSISTS ACROSS THE CONUS WITH A DEEP
TROUGH OVER THE ROCKIES AND A DOWNSTREAM RIDGE OVER THE TN/OH VALLEY
REGION. AN INITIAL OCCLUDED CYCLONE IN NE MT WILL MOVE NNEWD INTO
SK AS A TRAILING FRONT MOVES SLOWLY EWD ACROSS THE ERN DAKOTAS TODAY
AND WRN MN TONIGHT. FARTHER S...A REMNANT LEE CYCLONE PERSISTS IN
ERN CO...WITH THE PAC COLD FRONT EXTENDING SWD INTO W TX. THE FRONT
IS PRECEDED BY AN OUTFLOW BOUNDARY FROM OVERNIGHT CONVECTION...WHICH
NOW EXTENDS FROM ERN NEB SWD ACROSS EXTREME ERN KS...AND THEN SWWD
ACROSS CENTRAL OK INTO NW TX. E OF THE NRN PLAINS FRONT AND
CENTRAL/SRN PLAINS OUTFLOW...A BROAD WARM SECTOR COVERS AREAS EWD
ACROSS THE ENTIRE MS VALLEY REGION. THESE FRONTAL/OUTFLOW SEGMENTS
WILL PROVIDE THE PRIMARY FOCUS FOR SEVERE STORM DEVELOPMENT THROUGH
TONIGHT.
...CENTRAL TX TO ERN OK/WRN AR THROUGH TONIGHT...
OVERNIGHT CONVECTION PERSISTS FROM CENTRAL OK INTO NW TX...WITH NEW
DEVELOPMENT OCCURRING IN RESPONSE TO 40-50 KT LOW-LEVEL SLY FLOW
OVER THE LEADING EDGE OF THE COLD POOL. REGIONAL 12Z SOUNDINGS
REVEALED MODERATE INSTABILITY ACROSS OK/TX IN ADVANCE OF THIS
CONVECTION...WITH SOME WEAKENING OF CONVECTIVE INHIBITION NOTED
ALREADY ACROSS CENTRAL/N TX WHERE SURFACE HEATING IS OCCURRING
WITHIN CLOUD BREAKS. EXPECT THIS CONVECTIVE BAND TO CONTINUE TO
SLOWLY INTENSIFY THROUGH THE AFTERNOON ACROSS N TX AND ERN OK AS
DESTABILIZATION CONTINUES...AND AN EMBEDDED MID-UPPER SPEED MAX
ROTATES NEWD FROM THE TX BIG BEND. DEEP-LAYER AND LOW-LEVEL SHEAR
WILL BE FAVORABLE FOR ORGANIZED BOWING SEGMENTS AND EMBEDDED
SUPERCELLS WITHIN THE LARGER CONVECTIVE SYSTEM...AND MORE DISCRETE
STORM DEVELOP COULD OCCUR WITHIN THE WARM SECTOR FROM E TX INTO ERN
OK/WRN AR THIS AFTERNOON. GIVEN THE PREDOMINATELY LINEAR CONVECTIVE
MODE...DAMAGING WINDS WILL BE A PRIMARY CONCERN...ALONG WITH A FEW
TORNADOES AND LARGE HAIL WITH THE STRONGER EMBEDDED STORMS.
OVERNIGHT...THE UPSTREAM TROUGH WILL CONTINUE TO EVOLVE INTO A
CLOSED LOW OVER SE NM/FAR W TX. SUBSTANTIAL ASCENT AND A NOTABLE
LOW-LEVEL MASS RESPONSE TO THE NM/W TX TROUGH WILL SUPPORT
ADDITIONAL SEVERE STORM DEVELOPMENT TONIGHT IN CENTRAL TX ALONG THE
PAC COLD FRONT/REMNANT OUTFLOW BOUNDARY. THIS CONVECTION APPEARS
LIKELY TO EVOLVE INTO ANOTHER LARGE MCS WITH AN ACCOMPANYING RISK
FOR DAMAGING WINDS AND TORNADOES WITH EMBEDDED ROTATING STORMS...IN
ADDITION TO LARGE HAIL. RELATIVELY SLOW EWD PROGRESS OF THE BAND
AND TRAINING CONVECTION WILL ALSO RESULT IN LOCALLY HEAVY RAINFALL.
...MO/IA NWD TO THE ERN DAKOTAS/WRN MN THROUGH TONIGHT...
BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 50S BENEATH STEEP MIDLEVEL
LAPSE RATES WILL SUPPORT A CORRIDOR OF WEAK-MODERATE INSTABILITY IN
ADVANCE OF THE COMPOSITE OUTFLOW BOUNDARY IN MO/IA...AND THE SURFACE
FRONT ACROSS THE ERN DAKOTAS. SOMEWHAT UNIDIRECTIONAL PROFILES WILL
SUPPORT A RISK FOR ISOLATED DAMAGING WINDS/HAIL WITH A BROKEN BAND
OF STORMS ALONG/AHEAD OF THE FRONT THIS AFTERNOON/EVENING ACROSS THE
ERN DAKOTAS/WRN MN. STORM COVERAGE IS MORE CERTAIN FARTHER S INTO
MO/IA WHERE CONVECTION IS EXPECTED TO INTENSIFY THIS AFTERNOON ALONG
THE COMPOSITE OUTFLOW BOUNDARY NOW MOVING INTO WRN MO/IA. SOMEWHAT
STRONGER LOW-LEVEL SHEAR /COMPARED TO FARTHER N/ WILL PROMOTE A RISK
FOR EMBEDDED ROTATING STORMS IN A PREDOMINATELY LINEAR CONVECTIVE
MODE...WITH AN ATTENDANT RISK FOR DAMAGING WINDS/ISOLATED TORNADOES.
..THOMPSON/LEITMAN.. 03/19/2012
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