DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 112001
SWODY1
SPC AC 111958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0158 PM CST SUN NOV 11 2012

VALID 112000Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS EAST TX AND PORTIONS OF
AR/LA...

...EAST TX/ARKLATEX TO OZARKS/LOWER MS VALLEY...
LITTLE CHANGE TO PRIOR FORECAST REASONING...REFERENCE TORNADO WATCH
676 AND RELATED MESOSCALE DISCUSSIONS. OUTLOOK ADJUSTMENTS WERE MADE
IN ACCORDANCE WITH THE ADVANCING COLD FRONT...IN ADDITION TO
REDUCING HAIL PROBABILITIES GIVEN WEAK BUOYANCY/CONVECTIVE MODE.
WHILE DESTABILIZATION WILL REMAIN HINDERED BY APPRECIABLE CLOUD
COVER...LOWER TO MIDDLE 60S F SURFACE DEWPOINTS ARE CONTRIBUTING TO
AS MUCH AS 750-1250 J/KG OF MLCAPE AT MID AFTERNOON ACROSS EAST TX
IMMEDIATELY AHEAD OF THE EAST-SOUTHEAST MOVING COLD FRONT. PER
REGIONAL WSR-88D VWP DATA AND A SPECIAL 18Z OBSERVED SOUNDING FROM
LITTLE ROCK...MODEST LOW-LEVEL VEERING IMMEDIATELY BENEATH VERY
STRONG DEEP LAYER SOUTHWESTERLIES WILL CONTINUE TO SUPPORT THE
POSSIBILITY OF A FEW SUPERCELLS ASIDE FROM A DOMINANT LINEAR MODE
WITH POSSIBLE BOWING SEGMENTS. A TORNADO OR TWO WILL REMAIN POSSIBLE
ALONG WITH WIND DAMAGE...WITH THE SEVERE POTENTIAL STILL EXPECTED TO
GRADUALLY DIMINISH THIS EVENING.

..GUYER.. 11/11/2012

.PREV DISCUSSION... /ISSUED 1027 AM CST SUN NOV 11 2012/

...ERN TX/SERN OK INTO AR AND NRN/WRN LA...
HIGH AMPLITUDE UPPER TROUGH IS EXPECTED TO CONTINUE MOVING EWD
ACROSS THE CENTRAL US THROUGH TONIGHT AS THE STRONGEST WINDS ALOFT
ROTATE THROUGH THE ERN PERIPHERY OF THE SYSTEM. AT THE SURFACE...A
LOW OVER NWRN ONTARIO WILL MOVE NNEWD TOWARD JAMES BAY AS A STRONG
COLD FRONT...CURRENTLY FROM WRN WI INTO CENTRAL MO...SERN OK AND
SWRN TX...PROGRESSES EWD/SEWD TO A LAKE HURON/CENTRAL KY/CENTRAL
MS/TX GULF COAST LINE BY 12/12Z.

AN AXIS OF LOW LEVEL MOISTURE IS PRESENT AHEAD OF THE COLD FRONT
FROM ERN TX INTO THE MIDDLE MS VALLEY WITH SURFACE DEW POINTS
RANGING FROM THE MID/UPPER 60S OVER TX TO THE MID 50S OVER NRN MO
AND ERN IA. THE ERN EXTENT OF THE MOISTURE AXIS HAS BEEN LIMITED BY
ANTICYCLONIC TRAJECTORIES ON THE WEST SIDE OF THE ATLANTIC COAST
SURFACE RIDGE...AND THE MOIST AXIS IS LIKELY TO GRADUALLY NARROW IN
WIDTH AS COLD FRONT ADVANCES EWD WITH TIME.

12Z REGIONAL RAOBS AT FWD/SHV/LZK/SGF EXHIBITED A PRONOUNCED CAPPING
INVERSION ABOVE 800 MB THAT HAD LIMITED DEEP CONVECTIVE DEVELOPMENT
IN THE WARM SECTOR UNTIL RECENTLY. HOWEVER...PRE-FRONTAL STORMS ARE
NOW EVIDENT OVER NERN TX AND GIVEN THE FAVORABLE LOW LEVEL
SHEAR...STORMS WILL BE MONITORED FOR INDICATIONS OF INTENSIFICATION
/SEE MD 2117 FOR MORE DETAILS/.

WIDESPREAD CLOUD COVER DOWNSTREAM FROM THE COLD FRONT IS EXPECTED TO
INHIBIT DIABATIC HEATING AND STRONG DESTABILIZATION THIS
AFTERNOON...BUT SUFFICIENT INSTABILITY EXISTS TO SUPPORT STRONGER
CONVECTIVE UPDRAFTS THIS AFTERNOON. CONVECTION-ALLOWING MODEL
GUIDANCE INDICATES WIDELY SCATTERED STORMS SHOULD CONTINUE TO
DEVELOP IN ADVANCE OF THE COLD FRONT WITH ADDITIONAL LINEAR
CONVECTION ALONG THE COLD FRONT DURING THE AFTERNOON. STRONG DEEP
LAYER AND LOW LEVEL VERTICAL SHEAR ALONG THE SERN EDGE OF THE UPPER
TROUGH WILL ENHANCE STORM ORGANIZATION AND INTENSITY WITH POTENTIAL
FOR A FEW SUPERCELLS AND BOWING SEGMENTS TO FORM. STRONGER STORMS
WILL BE CAPABLE OF PRODUCING DAMAGING WIND...ISOLATED LARGE
HAIL...AND POSSIBLY A FEW TORNADOES MAINLY DURING THE AFTERNOON.
THE SEVERE THREAT SHOULD GRADUALLY DIMINISH TONIGHT AS BOUNDARY
LAYER COOLING COMMENCES AND THE UPPER TROUGH LIFTS NEWD AWAY FROM
THE HIGHER THETA-E AIR MASS.

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