DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 102001
SWODY1
SPC AC 101959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0159 PM CST THU JAN 10 2013

VALID 102000Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS SERN LA...PORTIONS
OF SRN MS AND SWRN AL...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
ACROSS ERN PARTS OF THE OZARK PLATEAU IN MID SOUTH...

...CENTRAL/SRN LA TO SWRN AL...
RECENT TSTM DEVELOPMENT EAST OF KJAN APPEARS TO BE ATTENDANT TO
FORCING FOR ASCENT WITH AN MCV TRACKING NNEWD JUST TO THE NW-N OF
KJAN. AN INCREASE IN EFFECTIVE BULK SHEAR TO 50 KT WITH THE VECTORS
ORIENTED PARALLEL TO THIS CONVECTIVE LINE SUGGESTS LOCALLY DAMAGING
WINDS WOULD BE THE PRIMARY THREAT. THUS...THE SRN SLIGHT RISK AREA
HAS BEEN EXPANDED ENEWD.

OTHERWISE...THE EARLY AFTERNOON SURFACE ANALYSIS SHOWED A COLD FRONT
EXTENDING SWD FROM EAST CENTRAL-SERN OK THROUGH E TX. AN INFLUX OF
MOISTURE WILL PERSIST NWD THROUGH THE LOWER MS VALLEY TO THE MID
SOUTH AND SERN MO/SWRN KY. THE NEWD TRACK OF THE MID-UPPER LEVEL
CLOSED LOW /CURRENTLY CENTERED OVER SRN OK/ N OF THE LOWER MS VALLEY
WILL MAINTAIN THE SLOW EWD ADVANCEMENT OF THE QLCS THROUGH SERN MS
AND THE ADJACENT N CENTRAL GULF INTO SWRN AL. EXTENSIVE CLOUDS/
PRECIPITATION AND WEAK LAPSE RATES WILL CONTINUE TO LIMIT THE
DEVELOPMENT FOR GREATER THAN MARGINAL INSTABILITY. HOWEVER...BACKED
SELY SURFACE WINDS ENHANCING LOW LEVEL SHEAR COMBINED WITH DEEP
LAYER SHEAR UP TO 40 KT SUPPORTS THE ONGOING POTENTIAL FOR SVR
WEATHER...WITH LOCALLY DAMAGING WINDS AND PERHAPS A TORNADO OR TWO
REMAINING THE MAIN THREATS.

...AR/SERN MO AND THE MID SOUTH...
NO CHANGES ARE NEEDED WITH THE NRN SLIGHT RISK AREA. LOW TOPPED
CONVECTION HAS FORMED OVER ERN OK AS THE COLD MIDLEVEL TEMPERATURES
AND FORCING FOR ASCENT ATTENDANT TO THE NEWD MOVING CLOSED LOW
SPREAD ATOP LOW LEVEL MOISTENING/SURFACE HEATING. THIS FORCING WILL
PROGRESS NEWD WITH THE POTENTIAL FOR TSTM DEVELOPMENT/SVR THREAT
LATER THIS AFTERNOON INTO THE EVENING ACROSS THE NRN SLIGHT RISK
AREA.

..PETERS.. 01/10/2013

.PREV DISCUSSION... /ISSUED 1030 AM CST THU JAN 10 2013/

...SYNOPSIS...
A MID/UPPER-LEVEL LOW OVER THE RED RIVER VALLEY WILL OPEN AND EJECT
NEWD THROUGH THE MID-MS VALLEY AS A NEGATIVELY TILTED SHORT-WAVE
TROUGH IN RESPONSE TO THE DEVELOPMENT OF AN INTENSE UPSTREAM TROUGH
ACROSS THE INTERMOUNTAIN WEST. THE FORMER WILL BE ATTENDED BY A
60-70 KT MIDLEVEL JET STREAK AND A CORRIDOR OF 500-MB HEIGHT FALLS
OF 100-150 M/12 HR OVERSPREADING THE OZARK PLATEAU TODAY.

IN THE LOW LEVELS...AN OCCLUDED SURFACE LOW OVER S-CNTRL OK AS OF
16Z WILL WEAKEN TODAY WITH THIS FEATURE REFORMING AT THE
INTERSECTION OF A WARM AND COLD FRONT WHICH WILL DEVELOP NNEWD
THROUGH WRN INTO N-CNTRL AR THIS AFTERNOON INTO EVENING. THE ERN
EXTENSION OF THE WARM FRONT WILL LIFT NWD THROUGH THE CONFLUENCE OF
THE MS AND OH RIVERS WHILE THE TRAILING COLD FRONT ADVANCES EWD INTO
THE LOWER MS VALLEY.

...CNTRL/SRN LA EWD INTO SWRN AL TODAY...

12Z SOUNDINGS SHOWED THE PRESENCE OF A MOIST...INFLOW AIR MASS TO
ONGOING QLCS...CHARACTERIZED BY BOUNDARY-LAYER DEWPOINTS IN THE MID
TO UPPER 60S AND LOWEST 100-MB MEAN MIXING RATIOS OF 13-14 G/KG.
WIDESPREAD CLOUDS AND WEAK MIDLEVEL LAPSE RATES WILL LIMIT THE
DEGREE OF DESTABILIZATION TODAY WITH THE SEASONALLY HIGH MOISTURE
CONTENT LARGELY CONTRIBUTING TO MLCAPE OF 250-750 J/KG.

THE GLANCING INFLUENCE OF THE MIDLEVEL TROUGH PASSING TO THE NW OF
THE REGION COUPLED WITH A SUSTAINED 30-40 KT SLY LLJ SHOULD SUPPORT
THE CONTINUED EWD PROGRESSION OF QLCS INTO SERN MS/SWRN AL BY THIS
AFTERNOON. GIVEN THE MOIST/LOW LCL BOUNDARY LAYER IN PLACE AND
MODESTLY STRONG LOW-LEVEL AND DEEP-LAYER SHEAR...EXPECT THE RISK FOR
EMBEDDED MESOVORTICES TO PERSIST WITH AN ATTENDANT THREAT FOR
LOCALLY DAMAGING WINDS AND PERHAPS A TORNADO OR TWO.

ADDITIONAL STORMS MAY DEVELOP THIS AFTERNOON TO THE W OF THE QLCS
ALONG THE COLD FRONT OVER CNTRL LA. SOME POTENTIAL FOR LOCALLY
STRONG WIND GUSTS WILL EXIST WITH THIS ACTIVITY INTO WRN MS THROUGH
EARLY EVENING.

...ERN PORTIONS OF THE OZARK/PLATEAU MID SOUTH THIS AFTERNOON AND
EVENING...

RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE UPPER 50S TO LOWER 60S WILL
ALIGN WITH 500-MB TEMPERATURES COOLING TO -16 TO -18 C AND POTENTIAL
BREAKS IN THE CLOUDS TO YIELD AFTERNOON MLCAPE VALUES APPROACHING
250-500 J/KG WITHIN THE NWD-EXPANDING WARM SECTOR. INCREASING
FORCING FOR ASCENT/HEIGHT FALLS IN ADVANCE OF THE EJECTING UPPER
TROUGH ARE EXPECTED TO FOSTER THE DEVELOPMENT OF TSTMS ALONG AND
AHEAD OF THE COLD FRONT THIS AFTERNOON ACROSS CNTRL AR.

DESPITE SOME VEER-BACK-VEER TENDENCIES...MODEL DERIVED HODOGRAPHS
ACROSS THIS REGION EXHIBIT MODERATELY STRONG LOW-LEVEL AND
DEEP-LAYER SHEAR WITH EFFECTIVE SRH OF 150-250 M2/S2 AND EFFECTIVE
BULK SHEAR OF 45-55 KT. GIVEN THAT SUFFICIENT INSTABILITY DEVELOPS
TO SUSTAIN TSTMS...THE POTENTIAL WILL EXIST FOR SUPERCELL AND BOWING
STRUCTURES CAPABLE OF DAMAGING WINDS AND POSSIBLE TORNADOES.

EXPECT THIS THREAT TO DIMINISH BY MID TO LATE EVENING OVER SERN MO
AND WRN TN OWING TO THE GRADUAL COOLING AND STABILIZATION OF THE
BOUNDARY LAYER.

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