SWODY1
SPC AC 291957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT FRI AUG 29 2008
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER
S-CNTRL/SWRN AZ...
...AZ/SERN CA...
18Z TUS SOUNDING AND CURRENT SURFACE OBSERVATIONS INDICATE THAT AIR
MASS IS SLOWLY DRYING OVER SERN AZ...PERHAPS DUE TO DOWNSLOPING
EFFECTS OF DEEP-LAYER ELY WIND FIELDS. HOWEVER...RUC OBJECTIVE
FIELDS AND MODIFICATION OF 12Z PHOENIX SOUNDING FOR CURRENT
CONDITIONS SUGGESTS THAT BOUNDARY LAYER OVER S-CNTRL/SWRN AZ IS
ALREADY MODERATELY UNSTABLE WITH MLCAPES APPROACHING 2000-2500 J/KG.
THERE IS SOME UNCERTAINTY AS TO WHETHER THE MODESTLY STRONG ELY
WINDS ON THE LARGE-SCALE WILL OVERWHELM SMALLER-SCALE DIURNAL
CIRCULATIONS...LIMITING THE NUMBER OF TSTMS THAT DEVELOP. SHOULD
THIS OCCUR...THE POTENTIAL FOR AN ORGANIZED TSTM COMPLEX CAPABLE OF
A MORE WIDESPREAD WIND THREAT WOULD DIMINISH.
HOWEVER...BASED ON THE OBSERVED THERMODYNAMIC AND KINEMATIC
PARAMETERS...SETUP APPEARS FAVORABLE ENOUGH TO WARRANT INCLUSION OF
HIGHER SEVERE PROBABILITIES AND A CATEGORICAL SLIGHT RISK.
...SRN OH VALLEY INTO THE SRN PLAINS...
SYNOPTIC COLD FRONT EXTENDS FROM WRN OH SWWD THROUGH THE OZARK
PLATEAU INTO THE TX PNHDL. AN OUTFLOW BOUNDARY REMNANT FROM
NOCTURNAL TSTM ACTIVITY PRECEDES COLD FRONT FROM NERN OK SEWD
THROUGH CNTRL AR INTO THE MS DELTA. THE COMBINATION OF STRONG
DAYTIME HEATING AND DEWPOINTS IN THE 70S HAS RESULTED IN THE
DEVELOPMENT OF A MODERATELY UNSTABLE AIR MASS THIS AFTERNOON WITH
MLCAPES OF 1500-3000 J/KG FROM OK INTO THE LOWER MS VALLEY.
TSTMS SHOULD CONTINUE TO INCREASE IN COVERAGE THIS AFTERNOON OWING
TO SUSTAINED CONVERGENCE ALONG ABOVE-MENTIONED BOUNDARIES AND
GROWING NUMBER OF STORM-SCALE COLD POOL INTERACTIONS. VERTICAL
SHEAR REMAINS QUITE WEAK...BUT THE DEGREE OF INSTABILITY SUGGESTS
SOME POTENTIAL FOR A FEW STRONG PULSE-TYPE STORMS CAPABLE OF GUSTY
WINDS AND PERHAPS SOME HAIL.
...S-CNTRL/SERN CO...
AFTERNOON VISIBLE SATELLITE IMAGERY INDICATES DEEPENING CUMULUS
DEVELOPMENT ALONG THE HIGHER TERRAIN OF CNTRL CO. ELY LOW-LEVEL
FLOW OVER THE ADJACENT HIGH PLAINS IS SERVING TO: 1) ENHANCE THE WWD
FLUX OF AN INCREASINGLY MOIST AND UNSTABLE AIR MASS INTO AREA...AND
2) PROMOTE OROGRAPHIC ASCENT ALONG THE FOOTHILLS. AS MENTIONED IN
PREVIOUS DISCUSSION...12Z GJT SOUNDING INDICATED THE PRESENCE OF
SOME STRONGER HIGH-LEVEL FLOW...BUT IN GENERAL LOW TO MIDLEVEL SHEAR
WILL REMAIN RATHER WEAK. NONETHELESS...THE PRESENCE OF THE STEEP
LAPSE RATES AND RESULTANT MODERATE CONVECTIVE INSTABILITY WILL BE
SUPPORTIVE OF STRONGER STORMS CAPABLE OF HAIL AND LOCALLY DAMAGING
WINDS.
..MEAD/KIS.. 08/29/2008
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