SWODY1
SPC AC 231958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0158 PM CST WED DEC 23 2009
VALID 232000Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE OZARK PLATEAU SWD INTO
CNTRL/ERN TX AND THE WRN HALF OF LA...
...OZARK PLATEAU INTO ERN TX/WRN LA...
TSTMS ARE ONGOING EARLY THIS AFTERNOON FROM NERN KS SWD THROUGH
CNTRL/ERN OK INTO ERN TX. THE NRN MOST ACTIVITY IS ASSOCIATED WITH
WEAKENING...LEAD SHORT WAVE TROUGH LIFTING NWD INTO THE MID MO
VALLEY. THE MAJORITY OF STORMS ARE LIKELY ELEVATED AND SITUATED TO
THE N OF ASSOCIATED SURFACE LOW /S OF EMP AS OF 19Z/ AND WARM FRONT
GRADUALLY MOVING NWD THROUGH ERN KS/CNTRL MO. CONVECTIVE
INSTABILITY IS FORECAST TO REMAIN QUITE SMALL...THOUGH THE COOL
THERMODYNAMIC PROFILES MAY SUPPORT SOME HAIL IN THE STRONGER
STORMS.
THE INTERMEDIATE CLUSTER OF TSTMS OVER OK ARE PRESENT ALONG AND E OF
SURFACE FRONT EXTENDING FROM SURFACE LOW NEAR EMP SSWWD TO SECONDARY
WAVE NEAR ADM. THESE STORMS MAY BE SURFACE-BASED OR NEARLY
SURFACE-BASED WITH A N-S AXIS OF LOCALLY STRONGER HEATING WHICH HAS
DEVELOPED AHEAD OF THE FRONT. SHORT TERM MODEL DIAGNOSTICS AND
WATER VAPOR IMAGERY SUGGEST THAT A WEAK MIDLEVEL PERTURBATION MAY BE
LIFTING NEWD ACROSS THE AREA...PERHAPS PROVIDING FAVORABLE
BACKGROUND FORCING FOR ONGOING ACTIVITY. PRIMARY UNCERTAINTY IS
DURATION AND POTENTIAL SEVERITY OF STORMS GIVEN NARROW INSTABILITY
AXIS WHICH WILL LIKELY NOT TO EXPAND GIVEN ELY LOW-LEVEL SURFACE
TRAJECTORIES ORIGINATING FROM RAIN-COOLED AIR MASS OVER AR. WHILE
ISOLATED SEVERE WEATHER WILL REMAIN POSSIBLE THIS AFTERNOON INTO
TONIGHT...IT APPEARS THAT THE MORE ROBUST SEVERE THREAT WILL REMAIN
S OF THE RED RIVER.
OVER ERN TX...TSTMS HAVE SLOWLY BEEN INCREASING IN COVERAGE AND
INTENSITY WITHIN N-S ORIENTED CONFLUENCE BAND WHERE LOW-LEVEL
MOISTURE FLUX IS BEING ENHANCED...ALONG WRN EDGE OF 30-40 KT SSWLY
LLJ. HERE...LEDBETTER TX PROFILER INDICATES LITTLE LOW-LEVEL
HODOGRPAPH CURVATURE BUT 20-25 KT OF SPEED SHEAR IN THE LOWEST 1 KM.
THE ENTIRE WIND PROFILE WILL IMPROVE WITH TIME THIS AFTERNOON INTO
TONIGHT AS STRONGER WIND FIELD ATTENDANT TO UPSTREAM SYSTEM
OVERSPREADS THE REGION. GIVEN THE MOISTENING BOUNDARY
LAYER...WEAKENING CIN AND RESULTANT MLCAPE OF 500-1000 J/KG...SETUP
WILL BECOME INCREASINGLY FAVORABLE FOR SUPERCELLS EMBEDDED IN LARGER
CONVECTIVE SHIELD WITH THE THREAT FOR TORNADOES...HAIL AND DAMAGING
WINDS.
ARRIVAL OF STRONGER FORCING FROM THE W TONIGHT MAY INITIATE AN
ADDITIONAL BAND OF STORMS ALONG INTENSIFYING COLD FRONT W OF THE
I-35 CORRIDOR. THIS STORM DEVELOPMENT WILL GRADUALLY OVERTAKE
ONGOING ACTIVITY OVER E TX WITH A LINEAR CONVECTIVE SYSTEM BECOMING
THE DOMINANT MODE BY LATE TONIGHT INTO THURSDAY MORNING. AS THIS
TRANSITION OCCURS...DAMAGING WINDS WILL BECOME THE PRIMARY SEVERE
WEATHER HAZARD.
..MEAD.. 12/23/2009
.PREV DISCUSSION... /ISSUED 1027 AM CST WED DEC 23 2009/
..SYNOPSIS...
MID MORNING WV IMAGERY AND 12Z HAND ANALYSIS SHOWS COMPLEX AREA OF
LOW PRESSURE ALOFT OVER AZ/NM. A 100 KT WIND MAX AT 500 MB OVER SAN
DIEGO INDICATES UPPER LOW SHOULD CONTINUE SEWD TODAY INTO FAR WRN
TX/SRN NM...BEFORE TURNING EAST TONIGHT AS JET MAX MOVES TO THE BASE
OF THE UPPER TROUGH. WV IMAGERY ALSO SHOWS ONE WEAK WAVE MOVING NEWD
THROUGH SERN KS...AND ANOTHER MID/HIGH LEVEL TROUGH SHIFTING EWD
INTO WRN AR AND LA. SATELLITE SHOW MID/HIGH LEVEL DRYING/POSSIBLE
SUBSIDENCE OVER A LARGE PORTION OF TX AND THIS WAS SUPPORTED WITH
500 MB ANALYSIS OF THERMAL RIDGE OVER WRN/CENTRAL TX.
AT THE SURFACE...A WEAK SURFACE WAVE WAS LOCATED IN SERN KS...IN
ASSOCIATION WITH WAVE ALOFT. COLD FRONT TRAILED SWWD FROM THE LOW
THROUGH CENTRAL OK...AND THEN WSWWD INTO EAST CENTRAL NM. THE KS LOW
WILL WEAKEN...AS SECONDARY AREA OF LOW PRESSURE DEVELOPS ALONG FRONT
IN E CENTRAL NM...AND DEEPENS AS IT SHIFTS EWD ACROSS TX THROUGH THE
PERIOD...WITHIN PRIMARY AREA OF LARGE SCALE FORCING.
...OZARKS REGION...
CONVECTION ASSOCIATED WITH KS WAVE...ERN KS INTO NERN OK...WILL
SHIFT EWD THROUGH THE AFTERNOON. ALTHOUGH THE BOUNDARY LAYER IS
EXPECTED TO REMAIN STABLE...STEEP MID LEVEL LAPSE RATES AND MUCAPES
AOB 500 J/KG MAY MARGINALLY SEVERE HAIL WITH SCATTERED STORMS THIS
AFTERNOON AND TONIGHT.
...SRN OK/SWRN AR SWD INTO THE ERN HALF OF TX...
WEAK BAND OF CONVECTION CONTINUES FROM VCT TO SHV IN ZONE OF LOW
LEVEL WARM ADVECTION. LIGHTNING HAS DECREASED WITH THIS ACTIVITY
THROUGH THE MORNING HOURS...LIKELY DUE TO SOME WARMING AND
STRENGTHENING CAP ALOFT. WITH BOUNDARY LAYER WARMING...A FEW OF
THESE STORMS MAY BREECH THE CAP LATE THIS AFTERNOON. SUFFICIENT
SHEAR AND INSTABILITY WOULD SUPPORT SUPERCELLS.
HOWEVER...AS LARGE SCALE FORCING SPREADS INTO THE WRN PORTIONS OF
NRN/CENTRAL TX THIS AFTERNOON...MORE INTENSE CONVECTION APPEARS
LIKELY IN THIS REGION. STEEP MID LEVEL LAPSE RATES COMBINED WITH
DEWPOINTS IN THE MID 60S WILL RESULT IN MLCAPES NEAR 1500
J/KG...AHEAD OF SURFACE LOW/SEWD MOVING COLD FRONT. DEEP LAYER SHEAR
WILL INCREASE AS STRONGER WINDS ALOFT STRENGTHEN...AND SUPPORT
SUPERCELLS. A FEW TORNADOES...LARGE HAIL...AND DAMAGING WINDS ARE
EXPECTED WITH THESE STORMS AS THEY SHIFT EWD THROUGH TX LATE THIS
AFTERNOON AND INTO TONIGHT.
AS THE STORMS PROGRESS EWD INTO DEEP ERN TX AND EVENTUALLY INTO SWRN
AR/LA TONIGHT...BACKING DEEP LAYER FLOW/SHEAR VECTORS AND STRONG
FORCING FOR ASCENT SHOULD FAVOR A SQUALL LINE EVOLVING. WHILE THE
PRIMARY THREAT WILL BECOME WIND DAMAGE...THE THREAT FOR A TORNADO OR
TWO WILL EXIST WITH EMBEDDED BOWS/SUPERCELLS.
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