SWODY1
SPC AC 170537
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT TUE APR 17 2007
VALID 171200Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
OVER SRN OK/NRN TX INTO THE ARKLATEX...
..SYNOPSIS...
AMPLIFIED YET PROGRESSIVE LARGE-SCALE PATTERN WILL CONTINUE THROUGH
THE DAY ONE PERIOD...WITH PRIMARY FEATURE OF INTEREST BEING MID AND
UPPER-LEVEL LOW WHICH WILL GRADUALLY WEAKEN AS IT TRANSLATES FROM
THE SRN HIGH PLAINS INTO THE CNTRL GULF COAST STATES BY WEDNESDAY
MORNING. IN THE LOW-LEVELS...ATTENDANT SURFACE LOW WILL DEVELOP
GENERALLY EWD FROM THE VICINITY OF THE TX/NM BORDER THROUGH N TX
INTO THE LOWER MS VALLEY BY THE END OF THE PERIOD.
..SRN OK/NRN TX INTO THE ARKLATEX...
17/00Z REGIONAL SOUNDINGS AND CURRENT GOES SOUNDER PW LOOP INDICATE
LOW LEVEL MOISTURE GRADUALLY INCREASING THROUGH SRN AND CNTRL TX
BENEATH A PRONOUNCED ELEVATED MIXED LAYER. LATEST SHORT TERM MODEL
GUIDANCE SUGGESTS THAT CAPPING/WARM MID LEVEL TEMPERATURES WILL
CONTINUE TO LIMIT INSTABILITY TODAY ACROSS CNTRL AND SRN TX DESPITE
A CONTINUED INCREASE IN BOUNDARY LAYER MOISTURE. THE GREATEST AIR
MASS DESTABILIZATION IS EXPECTED TO OCCUR INVOF SURFACE AND
MID-LEVEL LOWS OVER N TX WHERE MID-LEVEL COLD POOL WILL BE COLOCATED
WITH NWRN EDGE OF LOW-LEVEL MOISTURE AXIS /I.E. LOW TO MID 50
DEWPOINTS/...EFFECTIVELY CONTRIBUTING TO MLCAPES OF 500-1000
J/KG...MUCH OF WHICH WILL BE CONTAINED BELOW 500 MB.
TSTMS WILL BECOME INCREASINGLY LIKELY BY AFTERNOON INITIALLY OVER
THE TX PNHDL/W TX WITHIN STEEP LAPSE RATE AIR MASS...BUT W OF
PRIMARY LOW-LEVEL MOISTURE AXIS. SOME HAIL/LOCALLY GUSTY WINDS WILL
BE POSSIBLE WITH THESE STORMS. MORE VIGOROUS TSTM DEVELOPMENT IS
ANTICIPATED BY MID/LATE AFTERNOON AHEAD OF SURFACE LOW AND PERHAPS
SWD ALONG DRYLINE OVER N TX AS LARGE-SCALE FORCING FOR ASCENT
ASSOCIATED WITH MIGRATORY UPPER LOW ACTS ON DESTABILIZING WARM
SECTOR.
FORECAST SOUNDINGS WITHIN THIS AXIS OF STRONGER INSTABILITY INDICATE
RELATIVELY STRONG WIND FIELDS ABOVE 6-7 KM...NEAR AND ABOVE THE
ANTICIPATED EL HEIGHT. AS SUCH...MUCH OF THIS SHEAR WILL LIKELY NOT
BE REALIZED BY MATURE STORMS WITH EFFECTIVE BULK SHEARS IN THE 25-35
KT RANGE. THIS MODEST BULK SHEAR COUPLED WITH 0-3 KM SRH OF 100-150
M2/S2 INDICATE SOME POTENTIAL FOR LOW-TOPPED SUPERCELLULAR STORMS
WITH THE PRIMARY SEVERE THREAT BEING LARGE HAIL. A COUPLE OF
TORNADOES WILL BE POSSIBLE...ESPECIALLY WITH ANY STORMS NEAR THE SFC
AND 500 MB LOWS WHERE AMBIENT VERTICAL VORTICITY WILL BE LOCALLY
STRONGER.
THE WIND/HAIL THREAT WILL SHIFT EWD INTO THE ARKLATEX BY THIS
EVENING...WITH STORMS GRADUALLY WEAKENING LATER TONIGHT AS LOW-LEVEL
LAPSE RATES AND RESULTANT INSTABILITY DECREASE.
.MEAD/GRAMS.. 04/17/2007
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