SWODY1
SPC AC 060545
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1245 AM CDT WED AUG 06 2008
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL PLAINS INTO THE
CUMBERLAND PLATEAU...
...SYNOPSIS...
LARGE-SCALE PATTERN WILL UNDERGO AMPLIFICATION THIS PERIOD AS A
SERIES OF SHORT WAVE TROUGHS TRANSLATE SEWD THROUGH THE GREAT LAKES
REGION...EFFECTIVELY INTENSIFYING LONG WAVE TROUGH IN PLACE OVER ERN
N AMERICA. WITHIN THIS PATTERN...THE PRIMARY FEATURE OF INTEREST
APPEARS TO BE IMPULSE THAT WILL MOVE SEWD FROM THE NRN PLAINS INTO
THE OH VALLEY.
IN THE LOW LEVELS...ONGOING MCS OVER THE SRN OH VALLEY WILL LIKELY
DISPLACE THE EFFECTIVE SYNOPTIC BOUNDARY FARTHER S THAN LATEST MODEL
GUIDANCE SUGGESTS. BY MID AFTERNOON...THIS BOUNDARY IS EXPECTED TO
EXTEND FROM THE TN VALLEY NWWD TO NRN KS...TO THE N OF DEEPENING
SURFACE LOW OVER WRN KS. MEANWHILE...A COLD FRONT WILL PUSH SEWD
THROUGH THE NRN PLAINS AND UPPER GREAT LAKES...IN CONJUNCTION WITH
AFOREMENTIONED SHORT WAVE TROUGH.
...CNTRL HIGH PLAINS INTO THE CUMBERLAND PLATEAU...
CURRENT SURFACE OBSERVATIONS AND GOES SOUNDER IPW DATA INDICATE THAT
A MOIST AIR MASS EXISTS ALONG LOW-LEVEL BAROCLINIC ZONE FROM KS INTO
THE OH/TN VALLEYS WITH DEWPOINTS IN THE 60S TO LOW/MID 70S. THE
PRIMARY UNCERTAINTY IS HOW FAR S THIS BOUNDARY WILL BE DISPLACED BY
COLLECTIVE OUTFLOW FROM ONGOING MCS OVER THE OH VALLEY.
NONETHELESS...THIS MOISTURE COMBINED WITH MODESTLY STEEP LAPSE RATES
WILL CONTRIBUTE TO THE DEVELOPMENT OF A MODERATE TO STRONGLY
UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPES APPROACHING 2000-3500
J/KG.
DIURNAL HEATING COMBINED WITH MESOSCALE ASCENT ALONG THE SYNOPTIC
AND ANY ATTENDING OUTFLOW BOUNDARIES ARE EXPECTED TO CONTRIBUTE TO
AN INCREASE IN STORM COVERAGE BY AFTERNOON. THE SRN FRINGE OF
STRONGER HEIGHT FALLS ASSOCIATED WITH SHORT WAVE TROUGH TRANSLATING
SEWD THROUGH THE UPPER MIDWEST...MAY FURTHER ENHANCE STORM
DEVELOPMENT/EVOLUTION OVER PORTIONS OF NEB...KS AND MO.
THE STRONGEST DEEP-LAYER VERTICAL SHEAR WILL RESIDE ALONG CNTRL
PLAINS PORTION OF BOUNDARY WHERE ELY/SELY LOW-LEVEL WINDS WILL VEER
TO WNWLY AT 25-30 KT IN THE MIDLEVELS. HERE...POTENTIAL WILL EXIST
FOR SUPERCELL AND/OR BOWING STRUCTURES CAPABLE OF LARGE
HAIL...DAMAGING WINDS AND PERHAPS A BRIEF TORNADO OR TWO. VERTICAL
SHEAR WILL DECREASE WITH SEWD EXTENT...ESPECIALLY WITH EXPECTED
FARTHER S LOCATION OF SURFACE FRONT. STILL...ORGANIZED STORM
CLUSTERS APPEAR LIKELY WITH THE THREAT FOR DAMAGING WINDS AND
PERHAPS SOME HAIL.
...UPPER GREAT LAKES...
SCATTERED TSTM DEVELOPMENT IS EXPECTED THIS AFTERNOON ALONG AND
AHEAD OF COLD FRONT PUSHING SEWD ACROSS THE REGION. WHILE AIR MASS
WILL NOT BE OVERLY MOIST AND UNSTABLE...THE PRESENCE OF RELATIVELY
COOL MIDLEVEL TEMPERATURES ACCOMPANYING SHORT WAVE TROUGH WILL
CONTRIBUTE TO THE DEVELOPMENT OF STEEP LAPSE RATES AND WEAK
CONVECTIVE INSTABILITY WITH SBCAPES AOB 1000 J/KG. A FEW OF THE
MORE INTENSE STORMS WILL BE CAPABLE OF HAIL AND LOCALLY STRONG WIND
GUSTS GIVEN THE LAPSE RATES AND DEEP NWLY...UNIDIRECTIONAL WIND
FIELDS.
...NRN CA/SRN ORE...
A SHORT WAVE TROUGH WILL LIFT NWD THROUGH THE REGION TODAY PROVIDING
THE BACKGROUND FORCING FOR ASCENT FOR ISOLATED TO
SCATTERED...DIURNAL STORM DEVELOPMENT. FORECAST SOUNDINGS INDICATE
THE PRESENCE OF RELATIVELY STEEP LAPSE RATES WHICH WILL LARGELY
CONTRIBUTE TO SBCAPES OF 500-1000 J/KG. VERTICAL SHEAR WILL NOT BE
PARTICULARLY STRONG...BUT SOME HAIL AND/OR LOCALLY GUSTY WINDS ARE
POSSIBLE WITH THE STRONGER CELLS.
..MEAD/JEWELL.. 08/06/2008
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