MESO: Mesoscale Discussion 2051

ACUS11 KWNS 132330
SWOMCD
SPC MCD 132330
TXZ000-140030-

MESOSCALE DISCUSSION 2051
NWS STORM PREDICTION CENTER NORMAN OK
0630 PM CDT SAT OCT 13 2012

AREAS AFFECTED...PORTIONS CENTRAL/SE TX.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 132330Z - 140030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED SUPERCELLS MAY DEVELOP OVER DISCUSSION
AREA...WITH DAMAGING GUSTS POSSIBLE. TORNADO THREAT CANNOT BE RULED
OUT EITHER...THOUGH SPACE/TIME WINDOW APPEARS RELATIVELY SMALL.
ADDITIONAL CONVECTION IS EXPECTED TO MOVE INTO WRN PORTIONS OF THIS
REGION AFTER 02Z FROM WW 662...AND WILL BE COVERED WITH LATER
DISCUSSION(S) RELATE TO THAT REGIME.

DISCUSSION...SFC MESOANALYSIS REVEALS NO SUBSTANTIAL BOUNDARIES OVER
THIS REGION...EXCEPT FOR SUBTLE OUTFLOW ARC ASSOCIATED WITH ONGOING
CONVECTION THAT EXTENDS FROM LEON/BASTROP COUNTIES AS OF 23Z.
ADDITIONAL DEVELOPMENT IS EVIDENT IN REFLECTIVITY/VIS IMAGERY SWWD
ACROSS SAT AREA. ALTHOUGH WEAKLY FORCED IN LOW LEVELS...COMBINATION
OF LACK OF SUBSTANTIAL ELEVATED MIXED LAYER AND VERY RICH LOW-LEVEL
THETAE CONTINUES TO RESULT IN WEAK MLCINH WITH MLCAPE IN 500-1000
J/KG RANGE OVER THIS AREA. SFC DEW POINTS ARE COMMONLY 70S F IN
PRECONVECTIVE AIR MASS...NEAR N-S ORIENTED MOIST AXIS...WITH PW
2-2.25 INCH DETECTED BY GPS EQUIPMENT W OF I-45. FARTHER E...AIR
MASS BECOMES DRIER DUE TO PRIOR MIXING IN RELATIVELY PERSISTENT AREA
OF DIURNAL HEATING...THOUGH MOIST ADVECTION THROUGH REMAINDER
EVENING SHOULD SPREAD FAVORABLE PW BACK NWD THROUGH E-CENTRAL TX.

EXISTING BOUNDARY-LAYER INSTABILITY SEEMS MRGL TO OVERCOME STABLE
LAYER BETWEEN 850-700 MB IN FCST SOUNDINGS...AND MAINTAIN CONVECTIVE
CONTINUITY. THIS AREA IS ON SRN RIM OF FAVORABLE VERTICAL
SHEAR...WITH 35-40 KT EFFECTIVE SHEAR MAGNITUDES IN FCST SOUNDINGS.
HODOGRAPH DERIVED FROM LDB PROFILER WINDS YIELDING 150-200 J/KG OF
0-3 KM AGL SRH. INTERMITTENT STORM-SCALE ROTATION HAS BEEN
INDICATED IN CELL MOVING FROM BASTROP INTO LEE COUNTY...AND YET MAY
OCCUR WITH OTHER CELLS IN AREA AS WELL. MAIN LIMITING FACTORS WILL
BE WEAK LOW-LEVEL LAPSE RATES AND LACK OF MORE VIGOROUS MESOBETA
SCALE FOCI FOR ASCENT.

..EDWARDS/HART.. 10/13/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...SHV...HGX...FWD...EWX...

LAT...LON 29429926 31659635 31859521 31489457 30909453 30439467
29559559 29229735 29189895 29429926

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