SWODY1
SPC AC 080527
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1227 AM CDT MON SEP 08 2008
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF ERN KS/NERN OK
INTO CNTRL IL...
...THERE IS A SLGT RISK OF SVR TSTMS OVER S FL...
...SYNOPSIS...
PRIMARY EXTRA-TROPICAL FEATURE OF INTEREST THIS PERIOD WILL BE
MIGRATORY SHORT WAVE TROUGH WHICH WILL TRANSLATE EWD FROM THE NRN
PLAINS INTO GREAT LAKES REGION. ELSEWHERE...HURRICANE IKE WILL MOVE
WNWWD ALONG MUCH OF CUBA.
...CNTRL/SRN PLAINS INTO THE MID MS AND OH VALLEYS...
WEAK SURFACE LOW PRESSURE INITIALLY OVER SWRN OR S-CNTRL KS WILL
RAPIDLY DEVELOP NEWD TODAY ALONG RETREATING BAROCLINIC ZONE INTO THE
LOWER MO VALLEY BY AFTERNOON AND EVENTUALLY INTO THE LOWER GREAT
LAKES BY TUESDAY MORNING. IN THE WAKE OF THIS LOW...AN ASSOCIATED
COLD FRONT WILL PUSH SWD THROUGH THE CNTRL/SRN PLAINS AND MID MS
VALLEY.
ELEVATED TSTMS ARE EXPECTED TO BE ONGOING AT THE ONSET OF THE
FORECAST PERIOD ACROSS KS AND SRN NEB...DRIVEN LARGELY BY WAA AND
ISENTROPIC ASCENT ALONG THE NOSE OF NOCTURNAL LLJ. THIS ACTIVITY
WILL LIKELY CONTINUE THROUGH THE MORNING EWD INTO NRN MO ALONG
DIURNALLY WEAKENING AND VEERING LLJ. SOME HAIL WILL BE POSSIBLE
WITH THE MOST INTENSE STORMS THROUGH THE MORNING HOURS GIVEN THE
PRESENCE OF STEEP MIDLEVEL LAPSE RATES AND POCKETS OF MODERATE
CONVECTIVE INSTABILITY.
BOUNDARY LAYER DEWPOINTS IN THE 60S COMBINED WITH DIABATIC HEATING
ARE EXPECTED TO CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS BY
AFTERNOON /MLCAPES OF 1000-2000 J PER KG/ ALONG SRN FRINGE OF ANY
LINGERING CONVECTIVE DEBRIS AND AHEAD OF SURFACE FRONT FROM
W-CNTRL/SWRN IL WWD INTO ERN KS/NERN OK. HEIGHT FALLS ATTENDANT TO
UPPER TROUGH IN CONCERT WITH FRONTAL CONVERGENCE WILL SERVE TO FOCUS
VIGOROUS...DIURNAL TSTM DEVELOPMENT WITHIN A KINEMATIC ENVIRONMENT
CHARACTERIZED BY 35-45 KT OF DEEP-LAYER SHEAR. A CORRIDOR OF
STRONGER LOW-LEVEL SHEAR WILL RESIDE ALONG SURFACE LOW TRACK WHERE
POTENTIAL WILL EXIST FOR SUPERCELLS CAPABLE OF A TORNADO OR TWO.
OTHERWISE...LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE PRIMARY
THREATS WITH ANY OF THE MORE ORGANIZED STORM CLUSTERS THAT DEVELOP
DURING THE AFTERNOON AND EVENING HOURS.
...TN VALLEY INTO PARTS OF CNTRL PA/SRN NY...
LATEST MODEL GUIDANCE IS RELATIVELY CONSISTENT IN SUGGESTING THAT A
NE-SW ORIENTED BAND OF MAINLY ELEVATED STORMS WILL DEVELOP OVERNIGHT
IN ADVANCE OF COLD FRONT...FOCUSED PRIMARILY ALONG STRENGTHENING
SWLY LLJ. HERE...THE NEWD TRANSPORT OF AN INCREASINGLY MOIST AIR
MASS BENEATH A PLUME OF STEEP MIDLEVEL LAPSE RATES WILL RESULT IN
POCKETS OF ELEVATED CONVECTIVE INSTABILITY. GIVEN THE MODERATELY
STRONG CLOUD-BEARING SHEAR...THE POTENTIAL WILL EXIST FOR A FEW
STRONG STORMS CAPABLE OF SOME HAIL AND PERHAPS GUSTY WINDS.
...S FL...
AS MENTIONED ABOVE...LATEST NHC GUIDANCE TAKES HURRICANE IKE WNWWD
ALONG THE LENGTH OF CUBA. THIS MOTION WILL ALLOW LOW-LEVEL SHEAR TO
STEADILY INCREASE IN RIGHT /STORM-RELATIVE/ SEMI-CIRCLE OF TROPICAL
SYSTEM. THE GREATEST THREAT FOR SUPERCELLS AND A COUPLE OF
TORNADOES WILL LIKELY EXIST THROUGH THE DIURNAL HEATING CYCLE TODAY
WITH ANY LAND FALLING SPIRAL BANDS EXHIBITING MORE
DISCRETE...CELLULAR CONVECTIVE ELEMENTS.
...NM/FAR WRN TX...
WRN EXTENSION OF AFOREMENTIONED COLD FRONT WILL PUSH SWD THROUGH
MUCH OF WRN TX AND NM...PROVIDING THE FOCUS FOR TSTM DEVELOPMENT
THIS AFTERNOON INTO TONIGHT. MODEST BOUNDARY LAYER MOISTURE
/DEWPOINTS LARGELY IN THE 50S/ COMBINED WITH STEEP LAPSE RATES WILL
YIELD A MODERATELY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPES OF
AROUND 1000 J/KG. THIS INSTABILITY IN CONJUNCTION WITH 30-35 KT OF
DEEP-LAYER SHEAR WILL BE SUPPORTIVE OF A FEW ORGANIZED STORMS
CAPABLE OF SOME HAIL AND STRONG WIND GUSTS.
..MEAD/GRAMS.. 09/08/2008
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