SWODY1
SPC AC 140529
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 PM CST SAT FEB 13 2010
VALID 141200Z - 151200Z
...NO TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...BROAD BELT OF CYCLONIC FLOW ALOFT WILL PERSIST
FROM NRN PLAINS TO TX...AND ACROSS SERN STATES TO SRN/CENTRAL
APPALACHIANS. EMBEDDED/COMPACT CYCLONE ALOFT -- NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY OVER ERN SD -- IS FCST TO DIG SEWD OVER
STJ/MKC REGION AROUND 14/18Z...BEFORE PIVOTING EWD TO EVV-SDF
REGION BY 15/12Z. RELATED SFC CYCLONE -- NOW ANALYZED WITH WEAK LOW
OVER SWRN MO -- WILL STRENGTHEN CONSIDERABLY AND MOVE TO VICINITY
SWRN OH/NERN KY BY END OF PERIOD. TRAILING COLD FRONT WILL SWEEP
SEWD RAPIDLY ACROSS CENTRAL/SRN PLAINS AND OZARKS...REACHING SERN AR
AND RIO GRANDE VALLEY OF SW TX BY 15/00Z. DURING ENSUING 12
HOURS...FRONT WILL SURGE SWD OVER NERN MEX...SEWD OVER NWRN
GULF...AND EWD OVER MOST OF TN...AL AND NWRN GA.
ALTHOUGH NEITHER AREA APPEARS TO WARRANT SUFFICIENT UNCONDITIONAL
PROBABILITIES FOR GEN TSTM OUTLOOK ATTM...TWO AREAS APPEAR TO POSE
CONDITIONAL RISK WORTH MONITORING FOR POSSIBLE INCLUSION IN
SUCCEEDING OUTLOOKS.
...DEEP S TX...
DESPITE IMMATURITY OF RETURN-FLOW REGIME OVER THIS REGION...MOST
MODEL FCST SOUNDINGS SUGGEST THAT PREFRONTAL BOUNDARY LAYER MAY
MOISTEN/DESTABILIZE SUFFICIENTLY FROM LATE AFTERNOON INTO EARLY
EVENING TO YIELD WEAK BUOYANCY. OBSERVED OPEN-GULF SST AND FCST
RETURN-FLOW TRAJECTORIES INTO THIS REGION INDICATE SFC DEW POINTS
UPPER 50S TO LOW 60S F ARE POSSIBLE NEAR COAST AND S OF ABOUT
CRP...PRIOR TO FROPA. THIS LEADS TO MLCAPE POTENTIALLY REACHING
INTO 100-300 J/KG RANGE. TWO FACTORS LIMIT CONVECTIVE COVERAGE AND
DEPTH...HOWEVER...
1. LACK OF MORE ROBUST MID-UPPER LEVEL LAPSE RATE...WHICH APPEARS TO
STUNT DEPTH OF BUOYANT LAYER...AND
2. WEAKNESS OF PREFRONTAL WINDS NEAR SFC...LIMITING CONVERGENCE.
TSTMS SHOULD DEVELOP OFFSHORE...OVER NWRN GULF...AS FRONT IMPINGES
ON PROGRESSIVELY HIGHER BOUNDARY LAYER THETAE. HOWEVER...RISK OF
THUNDER INLAND APPEARS QUITE MRGL/CONDITIONAL.
...MS DELTA...CENTRAL GULF COAST STATES...
NARROW BUT STG BAND OF PREFRONTAL WAA AND MOIST ADVECTION IS
EXPECTED TO PRECEDE INCREASING COVERAGE WITH TIME OF FRONTAL PRECIP
AND PERHAPS EMBEDDED BAND OF SHOWERS. SOME WRF FCST SOUNDINGS
SUGGEST SUFFICIENT STEEPENING OF LOW-MIDLEVEL LAPSE RATES TO ALLOW
MUCAPE TO REACH 100-200 J/KG IN THAT PART OF WARM SECTOR IMMEDIATELY
ADJOINING COLD FRONT DURING 14/21Z-15/03Z TIME FRAME...AS LATTER
MOVES ACROSS NERN LA/SERN AR/WRN MS AREA. BY CONTRAST...DESPITE
THEIR REASONABLE DEVELOPMENT OF PRONOUNCED FRONTAL PRECIP/CONVECTIVE
BAND...ETA-KF AND SPECTRAL YIELD COMBINATION OF INSUFFICIENT
LOW-LEVEL THETAE TO YIELD MUCH IF ANY CAPE...AND WHAT CAPE IS
GENERATED FAILS TO REACH OPTIMAL ICING LAYERS FOR LTG PRODUCTION DUE
TO WEAK LAPSE RATES ALOFT. VERY ISOLATED LTG CANNOT BE RULED OUT IN
SUCH STRONGLY FORCED SETTING WITH NEAR-NEUTRAL LAPSE RATES.
HOWEVER...GIVEN STATE OF AIR MASS OVER GULF ATTM AND AMOUNT OF
MODIFICATION NEEDED TO YIELD BUOYANCY...PRIND THUNDER POTENTIAL IS
TOO CONDITIONAL/SPARSE TO WARRANT CATEGORICAL THUNDER AREA.
..EDWARDS.. 02/14/2010
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