SWODY2
SPC AC 231643
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1143 AM CDT SAT AUG 23 2008
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE NRN AND
CNTRL HIGH PLAINS...
...SYNOPSIS...
AN AMPLIFIED LARGE-SCALE PATTERN WILL EXIST OVER CANADA AND THE NRN
TIER OF STATES DURING THE DAY TWO PERIOD...FEATURING TROUGHS OVER
THE NERN PACIFIC INTO WRN CANADA/PACIFIC NW AND OVER ERN CANADA INTO
THE NRN STATES. IN THE LOWER LATITUDES...TROPICAL STORM FAY WILL
SLOWLY MOVE WWD ACROSS SRN MS INTO SERN LA.
...NRN/CNTRL HIGH PLAINS...
AN INCREASINGLY MOIST BOUNDARY LAYER WILL RETURN NWD ON BACKSIDE OF
SURFACE HIGH CENTERED OVER THE UPPER MS VALLEY INTO UPPER GREAT
LAKES...AND TO THE E OF STRENGTHENING LEE TROUGH. THIS PROCESS WILL
OCCUR BENEATH ERN EXTENSION OF EML/STEEP LAPSE RATE PLUME
ORIGINATING OVER THE ROCKIES...RESULTING IN A MODERATELY UNSTABLE
AIR MASS BY AFTERNOON WITH MLCAPES APPROACHING 1500-2500 J/KG.
CONVERGENCE ALONG LEE TROUGH...OROGRAPHIC FORCING AND PERHAPS A WEAK
IMPULSE CRESTING MIDLEVEL RIDGE AXIS ALL WILL CONTRIBUTE TO DIURNAL
TSTM DEVELOPMENT BY LATE AFTERNOON OR EARLY EVENING. WHILE MID AND
HIGH-LEVEL WIND FIELDS WILL NOT BE PARTICULARLY STRONG...FORECAST
HODOGRAPHS INDICATE CONSIDERABLE VEERING THROUGH THE LOWEST 3 KM
WITH EFFECTIVE BULK SHEAR STRENGTHENING TO AROUND 30 KT. GIVEN THE
STEEP LAPSE RATES AND MODERATE CONVECTIVE INSTABILITY...ENVIRONMENT
WILL BE SUPPORTIVE OF MARGINAL SUPERCELL STRUCTURES CAPABLE OF LARGE
HAIL AND LOCALLY STRONG WIND GUSTS.
...AL/MS/LA...
LATEST MODEL GUIDANCE SUGGESTS THAT THE CORRIDOR OF STRONGEST
LOW-LEVEL WIND FIELDS AND RESULTANT SHEAR/SRH WILL GRADUALLY ROTATE
FROM N TO W OF T.S. CENTER...SLOWLY BECOMING DISPLACED FROM ANY
POTENTIALLY STRONGER CONVECTIVE INSTABILITY THAT MAY DEVELOP IN ERN
SEMICIRCLE OF SYSTEM THROUGH THE DIURNAL HEATING CYCLE.
NONETHELESS...IT APPEARS THAT A SUFFICIENT OVERLAP OF MODEST
INSTABILITY AND LOW-LEVEL SHEAR WILL EXIST THROUGH FIRST HALF OF
PERIOD TO SUPPORT ISOLATED SEVERE STORMS CAPABLE OF DAMAGING WIND
GUSTS AND PERHAPS A BRIEF TORNADO OR TWO. A CATEGORICAL SLIGHT RISK
MAY BECOME NECESSARY IN SUBSEQUENT DAY ONE OUTLOOKS ONCE DETAILS
REGARDING INSTABILITY DISTRIBUTION AND MAGNITUDE BECOME MORE
CERTAIN.
..MEAD.. 08/23/2008
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